Placer Mining for Gold in California (Bulletin 135)

C.V. Averill

Placer Mining for Gold in California (Bulletin 135)

C.V. Averill · 1946 · Prospecting

The definitive reference on California's placer gold deposits. District-by-district coverage of the entire state — geology, production history, methods, and…

Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.

State Of California

Department Of Natural Resourci<3

WARREN T. H ANNUM, Director

Division Of Mines

Ferry Building, San Francisco

W. BURLING TUCKER State Mineralogist

San Francisco] Bulletin 135 [October 1946

Placer Mining For Gold In California

By CHARLES VOLNEY AVERILL

Contributing Authors F. W. Collins P. Malozemoff

L. Ti. HUELSUONK (1 AI. ROMAXOWIT/,

Olaf p. Jenkins H. A. Sawin

H. H. Symons

.C.S. tIBIlARV

Letter Of Transmittal

To His Excellency,

The IIoxorahle Earl AVarren,

Governor of tlie State of California

Sir: I have the honor to transmit herevitl\ for reprinting-, IJnlletin l:}5. Placer Mining for dohl in California, of the Division of Klines. Tliis volnnie was orioinally prepared under the direction of former State Mineralo<iist. Walter AV. Bradley, and published after his retirement, in October l!U(i Avhen W. Burling' Tucker held the same position. Since the issue of the book is now exhausted and there is still a continued demand for it by industry, a second printinji' is recommended by Olaf P. Jenkins, one of its authors, who is now Chief of the Division of Alines and State AIineralo>ist.

The volume is divided into four sections and an apinMulix : Blaccr minin<>' methods. (Jeology of placer deposits, I'rospectinji' and sampling- placer deposits. Placer mines by counties, and T.aws affecting placer mininu-. Eight authors have contributed to the book: Charles Volney Averiil. F. AV. Collins, L. L. Iluelsdonk, Olaf P. Jenkins, I'. Alalozemotf, C. AI. Komanowitz, II. A. Sawin. and 11. 1 1. Symons. Assend)ling and coordinating- the volume were done by C. A'. Averiil. Respectfully submitted,

AVakrkx T. llAXXTwr. Director Department of Xatui'al Uesourccs October 13, 1949.

Section Ii. Geology Of Placer Deposits 147

New technique applicable to the study of placers, by Olaf P. Jenkins 149

Section Iii. Prosi'Ecting And Sampling Placer Deposits— 217

Sampling - 219

Geophysical prospectiuf? 227

Section Iv. Placer Mines By Cotnties 229

Amador 231

Rutte 233

Calaveras 235

El Dorado 255

Fresno 257

Humboldt 258

Imperial 259

Kern 260

Los Anfjeles 260

Madera 261

Mariposa 261

Merced 262

Nevada 263

Placer 271

Plumas 277

Sacramento 278

San Bernardino 282

San Joaquin 282

Shasta 283

Sierra 285

Siskiyou 293

Stanislaus 304

Trinity -305

Tuolumne 313

Yuba 315

Deep gravels dredged successfully, by Herbert Sawin 317

Appendix. Laws Affecting Placer Mining 323

The Caminetti Law 325

Amendments to the 'Caminetti Act' 331

Definition of hydraulic minings, 333

Definition of hydraulic mining from Calif(jrnia Civil Code 333

Trinity and Klamath River Fish and Game District 334

Protection of domestic water supplies 335

Placer mining districts 336

(5)

CONTENTS— Continued

Illustrations

PaKc

I' 1. I>l;.i;lilic .In-.l::.- :}4

-. .M.ip slinw iii;c 'I'fili.iry ;;i;i\cl <li;iim(ls. .\<'\:i(l;i f'ouiity In pockot

Xuiiliciii Sicrni \cv;iil:i ;;c(il<.-ic niMji slmwiii'; Tcrtijiry river ohannHs

.iikI :\r..ili<.r I.n.Ir -..1.1 Im-]| In pocket

4. Xnilln'iii (';iliri(iiii:i 111,1)), sliowiiii; rixcrs niiil cracks wliich prodnrod

ijold In pocket

Viiiun- 1. riiiiii(i\c .i,',>I(l n-cnverv iiielliods — i.:in. rocker, nrnistre 14

2. C.-M i,;ni :iiid hrA,-.\ 2'2

Huckei- 24

4. ]{ockr-r p;irts 2.".

r,. Dip-hox 27

T-oii- loin 2S

7. P.odiiisf.n S.-mipliii!; M.-icliiiie

5. Denver :\re(li:iiiic:il Hold P;iii, siiijile iiiiif witli trommel

'.). T>(>nver AFecIiniiiciil (Jold I'mii. dii|ilex unit with h-oinmel ?,P,

1(1. l)r:i;;liiie dred-e under coiislnictioii in sliop

11. irimd-wiiicli for drn'liiie dredre 30

12. l*o\ver-\viiicIi for dr:if;1iiie dred-e 40

1.1. Trr.minel for dr:i;,dine dredge on track and trailer 40

14. ])r:i;:]iiie dredyc .sliowiiif; tronime], riflle-shiices. , and pump- screen 42

1.-. Cn.s.s .section of drede-ritHes 43

](i. Dragline dredge under constniction in field 44

17. l)ra:liiie dred},'e — early stafe of constrnciion 44

is. Diajcline dredy:e to accomnmdate .''-cn.yd. excavator 40

1!). Dryland dred;;e HO

20. Carrville Cold ('omi>any dredge ."4

21. Hepairiiifi iiucket-line. Yuha No. 20, showing' latest bucket-design HO

22. Perry Idler HR

2."i. P.ecker-IIopkins siii'rle-bucket dredge 61

24. lincket detail, liecker-IIopkins single-bucket dredge 62

Jig ari-angeni(>iits 70

20. Jig (esling set 72

27. Honglier .jigs, four-cell block 74

28. Flow-sheet for use of .iigs on O-cu. ft. dredge 75

20. Sand-drag, Siimpter Valley Dredging Company, Sunipter, Oregon — 76

30. Pieach-sand being worked with dip-box, northern Humboldt County 78

- 31. Method of spiling in loose ground ." 84

32. Flume for hydraulic mine under construction 02

:!3. Pipe install.-ition, 42- and r>4-inch 100

34. Cutting with giant 104

3.". Small giant in operation 104

Rnlde elevator used at Redding Creek mine, Douglas City, Cali- fornia , 108

37. liuble elevjitor in use at Redding Creek mine, Douglas City, Cali- fornia 110

.".S. Hydraulic elevator 111

Handling boulders with derrick 114

40. Sluice-box at hydraulic mine 116

41. Forking boulders along sluice at hydraulic mine 116

42. Stacking coiirse tailing with giant; sluice i.s under grizzly 117

43. Dredge-type rift's and wooden block ritHes 122

44. Looking down from hillside at sluic<- and uiulercurrents 126

4.'>. Amalgam retorts, bullion mold. crucible 138

40. Dre.lg.'d strip alon- Vnba Uiver 150

47. Tertiary Central Hill ehannel. Calaver.is County 151

45. Table Mountain, Tuolumne County , 154

40. Kffect of siream-bed irregularities; 'shingling' of boulders 155

(6)

CONTENTS— Continued

ILLUSTRATIONS— Continued

Page

no. Kxnmple of prpvolcaiiic topoRmpliy

.11. Miip of i)riiK-ipal pli.vsiop;rnpliic provinces of Cjilifornin liiS

r.2. Worl< of Vald.M- Dredinp Compjiiiy. Trinity River 160

T)."!. Tcrnice.s of Canyon Creek, Trinity County 160

54. Diagrams showinfj development of i)lacers 162

5.1. Quartz Hill mine, Siskiyou County 164

r>6. King Solomon mine. Siskiyou County 164

.17. Salyer mines. Trinity County 166

rS. Cross-section of gold-hearing desert stream 167

.10. 'Placer mining' beach sands at Santa Cruz 168

60. ]>iagrams of heach pl.acers 169

61. 'Cohhle wa.sh' and volcanic ash near Knights Ferry, Tuolumne

County 170

62. Diagram of down-dropped fault block 172

(".',. Sketch of dam made by landslide 172

64. Sketch map of early Tertiary channel and its delta 176

6.1. Diagram showing likely positions of gold concentrations in a river_ 176

(6. Diagrams of Tertiary gravel deposits 177

67. Diagrams of erosion and eddies in bends of a river 177

65. Diagram of effect of increased v<'locity on transporting power of a

stream 180

60. A'ertical section of a delta (detail) 182

70. Ideal cross-section of a delta 182

71. Diagram of oxbow loojis and an anastomosing stream 102

72. Diagrams illustrating stre.im i>iracy 106

7.". Diagrams of dendriiic and trellis drainage patterns 108

74. :\rai) of alluvial fans. San .Toaiiuin Valley 198

"7.1. T'dock diagrams showing tilting of Sierra Nevada 109

7(). Diagr.-immatic geologic cross-section of Table INIountain, near

Columbia. Tuolumne County 190

77. Mosaic of aerial photographs (.f Tal)le :Mountain 202

78. Index of mosaic of Table :Mountain 203

70. Surface of Table Mount.iin latite b>va flow 204

SO. Ideal cross-section of river in Sierra Nevada showing faulting of bed 20,5

81. Wallace Dredging Company, .3-cu. ft. dredge, operating 8 miles north

of lone in 1046 230

82. Pearch mine. Humboldt County 259

83. P.adger Hill i.roperty of S.in .Tuan Cold Company 267

84. Western Cold. Inc., Relief Hill mine 268

8.1. Sampling hydraulic bank 50 feet high, McGeachin Placer Gold

Mining Company 275

86. Natomas Ciunpany dredge 279

87. Thurmnn Gold Dredging Company 284

88. Depot Hill hydraulic mine 285

80. I'o\erty Hill Properties dredge under construction 286

00. Removing overburden ahead of dredging with carryall at Lancha

Plana, Amador County 286

01. William Richter & Sons dr.-igline dredge 286

02. Ruby mine, surface plant 288

03. Ruby mine, underground slusher hoist 288

04. Ruby mine, timbering. Slusher scraper at left 280

05. Gobi nuggets from the Ruby mine 290

00. Dragline dredge at Scandia mine 295

07. Dragline dredge at foccasin mine 296

08. Steel hull of dredge of Yreka Gold Dredging Company 302

00. Yreka Gold Dredging Company, dredge under construction 302

100. Goldfield Conso1id.it<>d Mines Company, hyxlraulic mine 306

101. Dredge (.f .Tunction City Mining Comjiany 306

102. Lincoln Gold Dredging Companv, dr.-igline dredge 309

103. We.-iver Drediiing C.ini.anv, dr.agline dredge 312

104. Yuba double st:icker dredges 314

105. Yuba No. 2( dredge under construction 316

106. Yuba No. 20 dredge, operated near Ilammonton, California 320

(7)

Abbreviations

a-e

alternating current (electric)

Ars

abrasion resisting steel (U. S. Steel Corporation)

carbon

cfs.

cubic feet per second

cu. ft.

cubic foot or feet

cu.yd.

cubic yard(s)

d-c

direct current (electric)

E.

east

ft.

foot or feet

gpm.

gallons per minute

H.

Humboldt Meridian

hp.

horsepower

hr.

hour(s)

Inf.Circ.

Information Circular (U. S. Bureau of Mines)

in.

inch(es)

kva.

kilovolt-amperes

lb.

pound (s)

M. M.D.

Mount Diablo Meridian

mg.

milligram (s)

min.

minute (s)

N.

north

no.

number

oz.

ounce (s)

R.

range

rpm.

revolutions per minute

S.

south

S.B.

San Bernardino Meridian

sec.

section (s)

sq.

square

T.

township

vol.

volume

W.

west

Section I

Placer Mining Methods

Small-Scale Methods

Introduction

The following paragraphs describing small-scale placer mining during the depression of the 1930 's are abstracted from a report by the Federal Works Agency, Work Projects Administration, and from the letter of transmittal of that report by Corrington Gill, Assistant Commissioner. ,

This report shows that hand placering for gold is a vanishing frontier enterprise from which it is now next to impossible to extract a living. Soon after the depression set in thousands of unemployed with their families attempted small-scale placer mining as a source of livelihood. During the early years of the rush to the creeks the number of would-be miners failing to find gold was 20 times greater than the number of miners who had been successful in recovering an amount sufficient for even one sale. Disillusionment was rapid, and by 1933, a year in which at least 100,000 men tried their hand at placer mining, departures greatly exceeded arrivals at the diggings. By 1937 the number seeking gold had dropped to approximately 22,000, of whom a fifth recovered no gold at all. Moreover, small-scale placer mining has generally offered emi)loyment only for a very short time even to those Avho had some success. About half of those who found any gold gave up the effort within a month, and three-quarters within two months. Because climate and stream conditions frequently limit the work-year, and because seasonal jobs in other industries sometimes are available at higher wages, even the comparatively small number of full-time miners worked only eight months out of the year.

The average gross earnings for the miners who found gold in Cali- fornia, where most of the hand placering is carried on, were $6.02 per week for the three years ] 935-37, and weekly income of nearly a third of the placer operators did not exceed $3.50. These figures represent gross earnings for a full Aveek's work; returns per calendar week are lower because of broken working time ; net returns are still smaller because of commissions paid to bullion buyers and necessary expenses incidental to mining.

When the low level of weekly earnings and the short periods of work are known it is not surprising that yearly returns from gold placering by hand methods are found to be pitifully small. Gross aver- age annual earnings per miner for California ranged from $44 to $59 in the years 1935-37.

The survey did reveal one small group of miners to whom placer- ing is important. These are the men to whom placering offers an opportunity for work in off seasons and to earn something between jobs. When lumber camps are idle, when no harvests are offering work, when shops are closed for repairs or' waiting for orders, placering provides

1 Xewcomb, K., Merrill, C. W., and Kiessling, R. L., Employment and income from Rold placering by hand methods : Work Project.s Administration, National Research J'roject, Rept No. E-14, 1940.

( l.-i )

PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Fig. 1. Primitive g(.kl recovery methi>as- pan, by courtesy of The Argonaut ; rei)rintcd from Calif orni Geology, April-July 19.1/,, p. til!.'.

Jounidl of Mines (inil

something to do even though the returns are small. In certain limited areas, therefore, placering may yield enough to men Avitli irregular jobs to be of marked aid to them even though it does not yield enough for support in the absence of other sources of income.

If placering is thus looked upon only as a supplemental source of income for residents of the areas with placer deposits, it can be made to fill a definite but very minor place in the economy of the few com- munities in which gold-bearing gravels are found and to help a few hundred men at most.

The needs of the unemployed in the early 1930 's caused many persons to grasp at any possible source of income, no matter liow small or temporary it might be. Moreover, perplexed local relief officials, who were as yet receiving no aid from Federal sources, welcomed any possible source of help for the long lines of unemployed that gathered at their offices.

At that critical time fabulous tales of rich gold strikes came to the unemployed and the relief officials. The reports were listened to eagerly by many, and the farther from the gold streams they spread, the more fantastic they became and the more readily they were believed and acted upon. The greater the distance, the greater was the urge to get to the streams. Many local relief officials even "staked" families to gasoline and food for a one-way trip to the new Eldorados.

The increase in the price of gold from $20.67 in 1932 to $25. 5G in 1933 and to $35.00 in 1934 made such stories seem even more plausible and helped further to stimulate the migration of men to the creeks, despite the unfortunate experiences related by most of those drifting back from the gold-bearing areas. Stories of those who succeeded in making a living and of the very few who made strikes continued to be magnified out of all proportion, both in jassing from mouth to mouth and in the press, and brought new recruits to the streams as late as 1937.

Sec. I] SMALL-SCALE METHODS 15

It is obvious to those versed in jrold milliner tliat the facts are greatly exajrerated in these stories. To tlie hard-pressed unemployed, llovever, these accounts sounded like the answer to their need. How could they know that for every one who made a strike in placer mining, tens of thousands would find little or nothing, that not more than a few score at most could possibly expect to develop a profitable lode mine, and that large amounts of capital would be required for most of these mines ? The experience of the thousands who are unsuccessful in placer- ing does not make n<'ws; the story of the man here and there who is lucky does. i\Iost of the accounts were stories of success, stories which were news but which were misleading to the unemployed.

Number of Small-Scale Placer Miners

Many thousands of unemployed and their families joined in the gold rush that followed the spread of such success stories. Creeks that later had only one or two placer miners per mile sometimes harbored 100 men or more per mile searching for precious metal in 1932-33. Of course no count was ever made of those who flocked to the gold-bearing streams, but 100,000 would seem a conservative estimate for 1932 and 1933. The number probably did not drop much until after 1933, for new men kept coming in considerable numbers until 1934. They came from greater and greater distances as the stories spread eastward, and they came rapidly enough to replace the disillusioned families which were leaving. If there was only one turnover from 1932 through 1933, it would mean that 200,000 men tried their hand at placering, and that there was one would-be miner for every 10 men who were at least 21 years of age in California in 1930.

The 12,422 small-scale miners recorded by the United States Mint as selling gold in California in 1937 sold metal valued at only $542,186, compared with worth $1,033,093 sold by 19,463 miners in 1935. It might be pointed out also that the greatest productivity was not reached until 1936, after the crowds had left and when those w-ho knew the business were able to work unhindered by scores of would-be placer miners.

Summary of Findings

Small-scale placer mining has certain advantages for the able-bodied unemployed. It provides a meager income to a few without requiring much in the way of training or capital. It enables them to work at any time without going through the sometimes hopeless process of find- ing an employer. And, in addition, mining has given many who took it up seriously a new sense of self-reliance, of independence, and of initiative. Such results have had a salutary psychological effect on many unemployed during hard times.

To a few who have mined onl}' internnttently and who have relied on the creeks to augment their incomes from other sources rather than to provide them with a living, placering has proved particularly helpful. It has enabled many men, together with their families, to have some occupation between jobs, and it has contributed more to the welfare of these individuals than the small financial returns might suggest. And to a very small proportion of the few who have stuck to the creeks fairly steadily, placer mining has proved profitable.

To some who dislike discipline and authority, placer mining has proved preferable to other ways of making a living. There are men wlio

PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

n

— r-' ttjtotoooocQotooocf — oTosOo of-fo to'coV —

5.874J62 23.487.604 1 51.818,604 113.643.986 117.664.005

13,037,995 12,662,718 "12.247.892 13.648.386 13.006.469 11.356.527 9.887.233 10.530,372 11.133.437 10.826.645

®.

10.752.381 11.067.815 11.570.781 11.572,647 13,833,679 12,835.084 11,013.474 8.690,174 8.662,879 Z,250.430

OS — aoO"--<o — iCeirt ciioo — Voo ca co loco o go Voo coo oMSmoiocw c) o oo 00 cj — oo mtooootoiooeeoo

Iis

sill

ep 00 O CO O CD OB CO M 00 Oi CM tc O 00 CO CO

OS V 00 to' ui t-T (N O CO

u3cor-.a

wDoTosNOOr-Tco'eo os

l-OCCOCQaatO-- octo CO

to — I'wil-Tto ac lA CO O — CO ovo MCO iCO — CO O 00

litpi 8§§il§§iig i

Sec. I]

Small-Scale Methods

oxonoo —

s

SS5;5Sg

s

ISIfi

5:

5gSSS?S

'5s§5

s

=gi5§

r-Siil

s

g

-ooooJ

B

S5::?"Sg

sa--

o"

s

immmus

iliiS

a

§

Mii

g

iiiSi

5°ii

§

gJSSSS

s

S2--'

. O O CO O lOO ) r-- C5 CM to 30

ot;cooeow50(M-j:> oi w-ito

"Vyfow' -v*" io:oco<M*

uj o V —" t£ cc lO tC

aoosoi oo--

lOiOOO

D 00 W5 OS CO Ol C

jS 2S"So*

Sfeggg

ao — -O-O OU5W5 U500IO

I —T co QC ir MOO CO ussoooo

55 — Ca-SSSu50 TT 00— OCMTfTOtO-W — "O

so uf irjo o — o cT eJ cRcotoci-v -ec*c en ro od

eg

ad ;;

i s'i i i siiii ic-; I

i J-|.-5.Q,T1 -all iTo;

I |ls.li III ss I

o -oi-- con c

„D.2-S-0'0'S "oj fe OS S S 3 "

IK IT,A( i:n MINIS*; roK <:(M) i.v cat.ifoknia [r.iill. i:")

tri livr on ii liiy wliirli tlicy 1 liciiisclvcs ciini tliroujili |)la-or iiiiiiiii-; niflicr timii In \\(irU for wiitrcs or to Jicccpt jnihlic aid. rhicei- iiiiniii<r luis ciiiililnl siicli iiicii 1o live tlicir own lives 1o some (l'<:i'('o at least.

>\notlier small roiip to wlioiii siiiall-seale |)Iai-eri!i<i lias been help- ful iiii-liules men with outside iiieonies or j)eiisions. These men would have had Mothiii<r to do il' they had lived in the eities, hut they can work as hard or as easily as they will on the creeks. Kiiowiujr tliat their pensions will enable them to live, they work at their own convenience and at their own rate of sjieed on the placer <rravels, addinjr a little to their income and takinr advantajre of the fact that living: co.sts are lower on the creeks tlian in town. Placer mininji: has enabled many retired or pensioned jiersons to enjoy healthful work in moderation, to increase their small incomes, and to dream of makin? a rich strike some day.

Men who have shown that they can live within their means and build up their e(piipment out of an income of a dollai* or two a day can sometimes secure backiip' for larmier placer ]irojects that require more capital and will return at least a livin<r wa<ie. p]ach year a few men demonstrate unusual ability to placer and to conserve their resources and are able to lea.se };ood bars and efiuijiment. Only a very few suc- ceed in this way, but they prove that it can be done.

All the men in these fjroups do not add up to 5 percent of tlie small- scale placer miners of the country. For 95 percent of those wiio try to dei>end on small-.scale placer mininjr for a Hviu}?, it has turned out to be a delusion and a snare, primarily because earniufrs are tragically low. The output per man-hour from liand methods of placering on the lean bars still available is too low to support life in modest comfort. Less than half of the nuMi who try it tiiul enoufrh {rold to hold tliem at the streams over a month, and half of tliose who stay over a month do not remain over 2 months. Even amon<:: the better full-time miners, half appear to net less than $7 per Aveek. The result is that most miners follow plaeerinfj only casually in the hope of having a "lucky break" or in an effort to earn an income to tide them over between other jobs.

Parnings from snudl-scale ]">lacer mining, which are too low to support individuals, are far too low to support a well-rounded family life. Even the more successful miners can make no provision for med- ical attention, good clothing, social life, reserves for emergencies, facili- ties for recreation, and other such needs. The small-scale j)lacer miner's family lives at a bare subsi.stence level and from day to day. The uncertain nature of the work — owing to tiu> fact that the gravels at any parti(!ular p(int may give out at any time and force the family to move — has the further disadvantage of discouraging provision for suitable or i)ermanent dwellings and the making or purchasing of furniture or household equipment. This asp(>ct of jdacering also makes it ])articu- larly diflicult for children to be educated satisfactorily.

Children are given very limited educational facilities in the moun- tain counties at best. When they are reared in tents and shacks and are moved from creek to creek, they have access to poor schools oidy and cannot iiojie to receive an education equivalent to that given children of more settletl families in the more populous sections. They are handi- capped in many other ways. Diets are unbalanced, medical facilities hard to secure, and social contacts .scarce.

See. I 1 SMAT,T,-S('Ai.i', Mi/rnons 1!)

l''iii;illy, rjiinilics find coiidil ions discourjijint:' hccansc* llie conniniii- ity life is s( iinsjil isTfictoi-y. Il is (juilc (lill'. i'l-om that of the oi'ijiin.d pionciM's or ovou o!' I'ai'in lainilics. J'ionocrs and i'annors tVol that th(\v the hmd and aro (l('V('h)|)in;- it; tlicy are the jx'oph' who count; they aro tlio coiniHiiiiity, and tlicy are able to iiiako a comniunity life of their own even with veiy limited physical facilities, liut the jlaeer miners are temporary interloi)ei"s. Tliey own no land and are not (levelopinji- the area ; they are livin<>' otf, or at best, in the community, not as i)art of it, and they do not have the resources with which to make a life of their own nor with which to purchase an entree to the life of tlie connnunity in which they are living. Famih' and social life are very circumscribed.

Not only was the life of Ihe small-scale placer miner unsatisfac.-tory, l)articularly if he had a family with him, but the future probably will briiig a declining level. Small-scale placer mining in the United States provided fewer than 6, ()()() men with an average recovery above $3.50 per week gi-oss for more than 1 month out of 12, and it supplied fewer than 'AoO men with that recovery for more than 6 months out of 12. Unless there is a sharp upward change in the price of gold, it probably will provide fewer and fewer men with even this much income and for shorter and shorter periods each year.

The reason for such unsatisfactory incomes may possibly be better understood when it is recalled that small-scale placer mining by hand methods is an attempt to extract a living from a parsimonious Nature by human muscle, with very little aid from tools. The only energy provided by other than human exertion is a little free water power and power drawn upon by about a third of the full-time miners who utilize gasoline engines to pump water. But even these miners, more fortunate than the rest, shovel gravel themselves.

Wherever human muscle, unaided by power equipment works against nature, it is an almost universal result that returns are very low unless the work requires great skill. This holds true for placer mining. If bars are exceedingly rich, as many of them were for a time in the late 1840 's and 1850 's, muscle power may extract returns for a time comparable with those won by skilled labor in urban centers. But when the bars are small, lean, and uncertain in their distribution and erratic in their content, as they are in most known auriferous areas available to small-scale miners in the United States today, hand labor expended on them generally cannot yield earnings comparable with wages.

Mechanized mining can still yield good returns in manj areas, even on beds with a lower gold content per yard than those being worked by hand, because the gold content is certain, the yardage is extensive, and the amount handled per man-day with the aid of powder machinery is many times the yardage one man can handle unaided by machinery. But even when beds are worked by powder, they must be extensive and must give a constant yield to be profitable. If they yielded well one day, little the next, and nothing the third, as do many bars worked by hand, they could not be made to pay no matter how much machinery each man could put to work.

In view of the character of the work and its low returns, the ques- tion naturally arises as to why and how men adapt themselves to this

20 PLACER MI NINO FOB GOLD IN CALIFORNIA [Bull. 135

jiioiieer type of life and its exceed inf,'ly low earnings. The adaptation those \vlio stick to the work is not so difTHcnlt as it niirlit appear, for the selective process (piickly weeds out those who cannot adjust them- selves readily and leaves those to whom the life does not seem strange and to whom it may even seem attractive. Men who cannot live on a steady diet of canned foods, flapjacks, and beans; who cannot repair their own equipment or fix the roof when it leaks; and who dislike soli- tude cannot long survive the life at the creeks.

Phrasing it dilTerently, th.e probability that a miner will adapt him.self to i)lacer mining may vary directly with his self-sufficiency. If he can live alone, take care of his own needs, work without super- vision, and live on a few cents a day, he may become a full-time, small- scale placer miner. len to whom such a life appeals, or men to whom it is not unattractive, can adapt themselves to placer mining, and some of them thrive physically on it. But the proportion of workers in California, or even in the country, who can meet such qualifieations is very small; .so the number who can nuike a success of or even last at placer mining is very limited. Men who can fix the roof if it leaks, or build it from scratch if necessary, can readily be found; but not many men can both fix the roof and stand living alone under it after working alone all day. 80 the process of adapting themselves to the creeks is primarily- one of selection ; mo.st of those who try it cannot adapt them- selves, and leave.

►Some idea of the difficulties facing a would-be miner entering gold-bearing terrain may be realized when it is recalled that many of the forty-niners failed on the creeks of California when gold was much more plentiful than it is now, and when it is further recalled that in the nearly 100 years during which gold has been actively mined, all the profitable areas have long since been patented or at least taken up as mining claims, or have been purchased for farming or other nonmineral purposes. Con.secpiently, a miner who has been successful in locating a place that looks promising will ordinarily find that someone else has established ownership to it a long time before.

About half of the miners interviewed who gave infoi-mation on this point (102 out of 201 miners) were working without making any effort to secure permission; were working with [permission; 24 owned the claims they were working (mostly claims that were .so poor that others had passed them by, but that did yield something) ; six i>aid ro;'alties of 10 to 20 percent; and two were supi)osed to pay royalties above fixed earnings. The rest worked under various sorts of agreements, sucli as acting as caretaker for property in return for the right to mine. Owners of rich bars of course will not freely jiermit unrestricted mining, but nuniy i)rivate owners of low-grade gravel that will not pay wages make no objection to its being mined without royalties provided the operation does not become a nuisance.

The sitimtion is sometimes dilTerent when the men attempt to work on the pid)lic domain, for it is the duty of (Jovernment officials to pro- tect public i)roperty, ami they have not been enthusiastic over the invasion of |)ubli(; lands by miners. The Forest Service, for instance, has a very useful policy of keeping a strip of land a (piarter of a mile to half a mile wide, on either side of major scenic liij.diways, in it,s primitive state. Its oflicials naturally object to the huildiuiior hovels

Sec. I] SMALL-SCALE METHODS 21

within this protected area, thoiijjh they sympathize Avith the men and aHow tliem to build lialf a mile back from the road. But this means that the miners must maintain their own drives to their shacks, which is a real hardship in muddy Aveather. The danger of forest fires is ever present, and the Forest Service also must be very careful that careless miners do not become a fire hazard. Game wardens may object to the lresence of the small-scale placer miners, who sometimes muddy waters and hunt or fish without regard to game laws. The muddying of water used for irrigation purposes may also create difficulties at times. River pollution is another problem where miners work on streams whose Avaters are used by towns or cities, and restrictions imposed by sanitary districts sometimes add to the miners' difficulties. One of the first adjustments the miners must make, consequently, is that of accommodating them- selves to property rights which deprive them of the chance to Avork the bv?st bars AA-hich already are privately owned, and to laAvs and regula- tions Avhich interfere Avith operations on the poorer bars on the public domain.

Those persons Avho insist on trying small-scale placer mining in spite of the above Avarnings Avill find methods described by Boericke.- Numerous practical suggestions by a man aaIio states that he has per- sonally made a living from small-scale placer mining over a period of years are contained in a recent book by Douglas. Small-scale devices described beloAV are suitable for sampling large gravel deposits to deter- mine Avhether the gold-content is sufficient to justify Avorking by machin- ery on a large scale. Descriptions of the pan, rocker, dip-box, and sluice-box are reprinted Avith minor changes and additions from an article by Symons.'*

Pan, Rocker, Dip-Box, and Sluice-Box

The equipment and operations described herein are among the simplest, and have been used in California to recover gold from placers since the days of '49. They are used not only for gold, but any hea\'y materials may be separated from lighter ones in this Avay. They are adaptable for the separation of cassiterite (stream tin), tungsten ore, cinnabar, platinum metals, and gem stones.

Gold-Pan and Batea

The gold-pan is used in prospecting for gold, in cleaning gold-bear- ing concentrates, and in the hand-Avorking of very rich deposits. It is a shalloAv pan which varies from 15 inches to 18 inches in diameter at the top, and from 2 inches to inches in depth, the sides haA'ing a slope of about 30°. It Aveighs from 2 to 3 pounds. It is made of a heaAy-gauge steel Avith the rim turned back over a heaAy Avire to stiffen it. Where amalgamating is to be done in the pan, it is either made of copper or has a copper bottom. AVhen used by a skilled operator, it has a capacity of from half a 3'ard to 1 yard in 10 hours.

The object of panning is to concentrate the heavier materials by Avashing aAvay the lighter. To do this most efficiently, all material

2Boericke, AA'illiam F., Pro.specting and operating sniaU gold placers, 2d ed., New York, John AA'iley & Sons, Inc., 1941.

'Douglas, Jack, Gold in placer: published by Jack Douglas, Box 21, Dutch Flat, California, 1944.

Symons, Henry H.. The pan, rocker, dip-box, and sluice-box: California Jour. Mines and Geology, vol. 30, pp. 126-135, 1934.

I'LACKU MlNIXCi roK (iOI.I) IN ('ALII'(ti;NIA

ir.ull. i:{5

Reinhitid from Cdli/i CcoliKjy, Ai>iil I), iit't

should be of as even a size as possible. The pan is filled about three- quarters full of 'ravel to be washed, then it is subinerjied in Avater. First the larjie p:ravel is picked out by hand, then the clay is broken up. after -which the operator raises the i)an to the of the water, inclininj; it slightly away from him, moving it with a circular motion combined with a slight jerk, thus stirring up the mud and light sand and allowing it to float oft".

This is continued until only the heavier materials remain, such as the gold, black sand and other minerals having a high specific gravity. These concentrates are saved until a large (piantity accumulates, after whidi the gold is separated from them. It may be i)icked out by hand, amalgamated with q\iicksilver, sometimes in a copper-bottomed pan. In some cases where the separation is extremely difficidt and the quality and (juantity justifies the concentrates are shipped to a smelter. Pan- ning may be best learned by watching an old-timer or experienced oper- ator at work, learning certain tricks in the trade from him. A clean 6- or 8-inch frying j)an makes an excellent prospecting or clean-up pan. It is well to burn out an iron pan after having used quicksilver in it, and then polish it with a soft rock or piece of brick, otherwise it may be impossible to see small colorjj or flakes of gold.

The batea is cone-shaped and is the equivalent of the pan. It is made of wood or sheet metal. It varies from 15 to 24 inches in diameter and has an angle from I.IO' to l.');')" at the apex. Many persons claim that wood will liold fine gold better than metal. The batea is in common use in Mexico, Central and South America, and Asia. A shallow wooden chopping bowl may be utilized as a substitute for the batea. This woidd be u.sed in the same niiiiincr as a pan.

Rocker

The rocker is a machine to save gold from auriferous .sands and gravels by concentration (sometimes in conjunction with amalgamation).

See. I] sMAiJ-scArii: Mr/rnoDR 2:{

Rockers vary <rroiitly in size. sliai)e, and <r(MU'ral eonstruction depend- ing on ideas of builders in different localities and on their experience. Desifjns vary also because of diffei'ent materials beinj; available and because of variations in the sizes of tlie ])articles of <ro]d to be recovered. Rockers vary in lenth from 24 to ()() indies or more, in Avidtli from 12 to 24 inclies, and in height from (i to 24 inclies. Some luive a sinjrle apron, and otliei's two ai)rons and sci-eens with lioles as much as half an inch in diameter. A <ireat variety of devices to recover the Kld is found : riffles of all kinds, blanket, carpet, rubber mat, cocoa mat, canvas, cowhide, burlap, and amal'amated copper plate. The writer would sugrprest as a fairly efficient and easy construction of riffles for a rocker, to clamp f-inch metal lath over a double thickness of blanket so that it can be easily removed for cleanin<i:. Of all wet placer methods for saving ?old, the rocker is one of the most economical on water for the amount of material handled. The average rocker when operated by two men has a capacity of about to 5 yards in 30 hours, using 100 to 800 gallons of water.

Construction. Rockers are built in three distinct parts, consisting of a body or sluice box, a screen, and an apron. The floor of the body holds the riffles in which the gold is caught. The screen catches the coarser materials and is a place where clay can be broken up to free it of all small particles of gold. The apron is to carry all material to the head of the rocker, and is made of canvas stretched loosely over a frame. It has a pocket or low place on which coarse gold and black sands can be collected.

The accompanying drawing (fig. 3) gives a suggestion for a knock- down rocker that can be built by any one. The six bolts are removed to dismantle the rocker for easy transportation. The material required to construct it is given in the following tabulation with dimensions in inches :

A End, one piece 1" x 14", 16" Ion}? B Sides, two pieces 1" x 14", 48" long C Bottom, one piece, 1" x 14", 44" long D jNIiddle spreader, one piece 1" x 0", 16" long E End spreader, one piece 1" x 4", ir" long F Rockers, two pieces 2" x 5", 17" long H Screen, about 10" square outside dimensions with screen bottom. Four pieces

of 1" X 4", 15:}" long and one piece of screen 16" square with i" or i" openings

or sheet metal perforated with similar sized openings. K Apron, made of 1" x 2" strips covered loosely with canvas. For cleats and apron,

etc., 27 feet of 1" x 2" is needed. Six pieces of §" iron rod 19" long threaded

2" on each end and fitted with nuts and washers. L The handle, in the drawing is placed on the screen, although some miners prefer

it on the body. AVhen on the screen, it helps in lifting the screen from the body.

If 1- by 14-inch boards cannot be obtained, clear flooring tightly fitted will serve, in which case about 12 feet of 1- by 2-inch cleats in addition to that above mentioned will be needed.

A dipper made of a tomato can (no. 2-i) and 30 inches of broom handle is also necessary. Through the center of each of the rockers a spike is placed to prevent slipping during operation. In constructing riffles, it is advisable to build them in such a way that they may be easily removed, so that clean-ups can be made more readily. Two planks about 2 by 8 by 24 iiiches with a hole in the center to hold the spike in the rockers, are also required. These are used as a bed for the rockers to work on and to adjust the slope of the bed of the rocker.

PLACKK MINING FOR OOr.O IN rAI,IKORMA

f Bui 1.135

Sec T

Small-Scale Methods

A,

—

2(> rLA( i:i< Mi\iN( roit hold in calii-oknia [liull. n")

Assembly. The jiarts arc cut fo si/c as sliowii on tlic drawinrr, fipure 4. The cleats on parts A, B, (', and I) are of 1- by 2-inch material and are fastened with nails or preferably screws. The screen (H) is )iailed tofjether and the handle (L) is bolted to one side. Corners of the screen should be reiufoi-ced with pieces of .sheetnietal because the screen is beinjr continually pounded by the fall of rocks when the rocker is in use. The apron (K) is a fi-aine nailed to<jrether, and canvas is fastened to the bottom, .joints af the corners should be stren{?thened with strips of tin or other metal.

Parts are a.s.sembled as follows: bottom (('), end (A) with cleats inside, middle spreader (1)) with cleat toward A, and end spreader (E) are placed in position between the two sides (B) as shown in figure 3. The six bolts are inserted and the nuts are fastened. Rockers (F) should be fastened to bottom (C) with screws. Apron (K) and screen (II) are set in i)lace. and the rocker is ready for use.

If one-quarter-inch lag screws ai'e driven into the bottom of each rocker about 5 inches to each side of the sj)ike, and if the head is allowed to protrude from the wood, a slight bump will be caused as the machine is worked back and forth. This additional vibration will help to con- centrate the gold. If these are used, metal strips should be fastened to the bed-plates to protect the wood from wearing.

Opcratiun. AVhen the ground to be worked has been found, the miner picks a ilace near his source of water for his rocker. The fii"st thing to do here is to set the bed-plates so that the spikes in the rocker fit in the hole in the i)late and so that the iloor has the i)roper slope. This slojie is decided according to the ground to be worked. AVhere most of the gold is coarse and there is no clay, the head bed-plate should be 2 inches to 4 inches higher tlian the tail bed-plate; where most of the gold is fine or clay is present or a combiiuition of both, this slope is les.sened sometimes to only an inch. It is hard to save very fine gold if very muddy water is used, as the operation does not let the fine gold settle out but rather fioats it off.

After the rocker is jilaced in i)osition, the screen box is filled with gravel, which is washed off by ])ouring water over this material with the dipper. The larger gravel, when clean, is either picked out with a fork or by hand and all clay is broken up into a nuid. Next the machine is rocked vigorously for several minutes, and water is added continu- ously. If all material that will ])ass through the screen has dx)ne so, the box is dumped and this operation is repeated until it is thought necessary to clean the apron. The apron should be cleaned several times a shift, as all coarse gold is caught there. The concentrates are placed in a pile for further cleaning. The riffles are cleaned whenever it is thought necessary, but not nearly as frequently as the apron, and the concentrates are saved for further cleaning. When a blanket is used, it should be wa.shed out carefully in a tub of water, as here a good percentage of the fine gold is found. All concentrates are cleaned further in a ])an. It is important to u.se the right amount of water. The use of too nnich water will carry the nuiterial through this machine too qjiickly. and with it nnich M.ld. When not enough water is used, it makes a mud which will not let the fine gold settle.

SlV. IJ

8Mai.L-Scat.E Mf.Tiiods

Fi<J. 3. A din-bcix or shi>rt sluice, with imn screen for riffles. J'li'iti) bu Tlios. Whitt : Driiittd froin Calitornia Journal o) Mines and Gt ohxni. AprU-.l iihi I'.i.i ',. p. 1 .! ',.

Dip-Box

This is a modification of the sUiiee-box and may be used where Avater is scarce and there is not enough grade for an ordinary sluice. It is portable and may be carried in an automobile. It will permit liandling: about as much dirt in a day as a rocker, though the larger stones Avill have to be thro-\vn out by hand.

The dip-box is simply a short sluice with a bottom of 1- by 12-inch lumber to which are nailed sides of three-quarter-inch or 1 inch by 6 inches. The back end piece may also be of 1- by 6-inch stuff and the lower end piece 1 or inches high. To catch the gold, the bottom of the box may be covered with burlap, canvas or thin cari)et. Over this, beginning 1 foot beloAv the back end of the box, may be 'laid a strip of lieavy wire sci-een of c|nartcr-iiich mesh (made from no. 13 or no. 14 Avire) 1 foot Avide by 3 feet long. r)in-lap and screen may be held in place by cleats along the sides of the box. The diji-box may be made () to 8 feet long. Those Avho use it often claim that practically all the gold will be saved in the first 3 feet. The box is given a steep grade by being set on small trestles, the one near the head end being about

i'LA( i:i{ MiMN(i lOR r.oi.n iv rAT.nouNrA

rP.nll.1S5

Kipriiitfd front Cdlifoniia Joiinuil of Mines and 0((ilofjU. Ainil- Jiilji in.i'i. II. t.i.;.

waist liitrh and 6 inelies to a foot lii<ilier than tlie lower one, near dis- char?e end. The dip-box is used by dumpinjr the sand and gravel, a small bncketl'ul at a time, into ti\e back end of box, then i)onrin<r water from a dipper, bucket or hose onto it until it is washed through the box, discharging over the lower end. The gold will lodge mostly in the .screen. Riffles nuiy be i)ut in the lower i)art of the box to stop gold passing the screen. Water should not be jioured too violently into the box. The larger stones must be thrown out by hand, unless the box is fitted with a hopper, or a screen.

Puddling Box

Where muddy or clayey material is to be sluiced, the first box of the string can be made into a "i)uddling box." This can be 3 feet wide by 6 feet long, or any convenient dimensions, with 6-inch or 8-inch sides. and no riffles. The clayey material can be .shoveled into this box and broken up with a hoe or rake before it passes into the main sluice. Lumps of clay in a sluice may pick up and carry away the gold particles. Long Tom

A long tom is an inclined trouirh used to concentrate auriferous earths and gravels. It has a greater capacity than a rocker, but also uses more water in operation, because the water is the carrying agent of the finer materials. The long tom is n.snally of crude co'n.struction, being built in two sections, the sluice-box, and the riffle-box (fig. fi). The slope is generally 1 inch to each foot in length, but this is varied as conditions warrant. The sluice-box is usually about 12 feet long and about 15 to 24 inches wide at the head or upper end, and 24 to 86 inches wide at the tail or lower end. and sides are about 8 inches high at the tail. A screen or i)iece of ])erforated sheet metal prevents the coarse material from going to the riffle-box. and at the head end is a flume or iron pipe from which the water is fed. The riffle-box is usually shorter than the sluice-box, and .slightly wider than the latter at the

Sec. I] SMAI>L-S('AM'; MKTIIODS 29

tail end. It begins just below tlie first oiK'ninji' in tlie screen, some- times bas a more gentle slope. Here tbe rifHes ai-e i)lace(l to catcli tlie gold. Tbe box is ol'ten lined witb eanvas as in the rocker, and it is best to build detachable riffles. The sluice-box should be made of 2-inch lumber to Avithstand the abrasion of the gravel. The capacity of a long tom is from 4 to 6 yai-ds in a 10-hour day, per man, two to four men working.

Operation. The groinid to be worked is shoveled into the sluice- box and waslied by the water coming from the liead end. One of the men will work the material in the trough with a fork, taking the coarser gravel out when washed clean and keeping the screen from clogging. Clean-ups are made when necessary, usually at the end of the day, but ex])erience might show that they should be made oftener.

Sluicing

►Sluicing is a method of Avorking auriferous gravels in a flume called a sluice-box, or in a ditch, and the method is then called ground sluicing. The sluice-box is a crude sloping flume or trough, having riffles on the bottom to catch the gold. Dimensions var,y greatly and are governed b}'' the amount of material to be washed through the sluice. The slope varies from 5 to 18 inches in a 12-foot length. The riffles also vary, sometimes there are several kinds in a single sluice, some of Avhich are quite elaborate and require considerable work in laying.

In the rocker and long tom, all the coarse materials are removed, but in the sluice all is allowed to pass through, or in some cases a grizzly is placed at the head of tbe sluice-box to catch the very coarsest of material, allowing much heavier gravel to enter than in the other devices previously described. This coarse material serves to grind and polish tbe gold, thereby cleaning it and making it easier to amalgamate and possibly freeing some material mechanical held.

In sluicing, much of the manual labor done in the preceding methods is eliminated, as the water does all of the carrying of the material. In some cases the mining is done hy hydraulicking or a stream of Avater is allowed to fall over a bank and in that way wash the material to the sluice. Sluicing requires more Avater than the methods previously described, the amount depending upon the material to be Avashed, and varying from 20 to 80 cubic feet of Avater to move 1 cubic foot of gravel. Coarse gravel requires more Avater than fine, but as the gradd is increased the amount of Avater required is lessened. The capacity of the sluice box is governed by its grade and amount of water available as Avell as its dimensions. In ground sluicing a ditch is dug along bed-rock and natural irregularities in the bottom furnish pockets Avhich catch the gold.

Riffles. Riffles are obstacles placed along the bottom of a sluice Avhich form pockets to catch gold by concentrating the heaA'ier materials. Numerous forms of riffles Avith innumerable modifications have been devised. Some of the best knoAvn are described in the folloAving para- graphs :

Common riffles or slat riffles are strips of AAood, iron, or steel extend- ing across the sluice box. The abrasion is so great on AA'Ooden riffles that replacement is required often and therefore other types of riffles are preferred in large-scale operations.

Pole riffles are frequently used. These are 2- to 4-inch peeled poles placed either across or lengthAvise of the sluice box. This type is used

pi,A( i;k minin<: row coi-o ix caf.ifornia [Hull. 135

Hiitlirisoi) .saiiip

Irs), of llodins

Miniufni till

with coarse inatcriai and is efticiont in concentrating? both coarse and fine fold.

Block riffles are made by pavinj; the floor of the sluice-box vith wood blocks cut across the grain, and four Indies or more hijjh depend- ing on the depth and width of the sluice. They are nailed to narrow slats on the end that is to re.st on the bottom of the sluice. The slats are naile<l to tlie sides of the blocks, so that a space is left between the rows of blocks at the top. Spaces between the rows of blocks form the riffles. The blocks may be made either .s(piare or round. This method is good for both coai'se and fine materials.

Kock or stone riffles are made by paving the floor of the sluice with rock, either stream [x'bbles or flat stones quan-ied for the iurpose. They are held in place by strips of wood nailed across the bottom at intervals. This method is good for both fine and coarse matei'ial, and extra good for cemented gravel.

Zig-zag riffl<'s are slats placed part way across the floor of the sluice box alternately from the sides.. Tliis type is good for fine material and concentrates in a similar way to panning.

An undercurrent is a wide flat sluice placed beneath the main sluice box and is used for the purpose of saving the tine gold. It is usually .') to 20 times as wide as the main sluice and fi-om 10 to 50 feet long. It receives its feed from a gi'i/./.ly or scr(>en placed in the floor of the main sluice-box. from which the fine material drops into a troujrh, which distributes the feed eveidy acro.ss the whole width. Undercur- rents usually have a greater slope than the main sluice, because the shallow stream is retarded more by friction.

Soo. T] s.MAiJ--srALr. mktiiods 31

Small-Scale Placer Machines A iVw siii}ill-s(jil(> iiiacliiii(>s for rocovory of fold from placer n-avels are described below because they are believed to be valuable for sampling large dejiosits to determine wlietliei- the gold-content is great enough to justify the use of a dragline dredge, bucket-ladder dredge, hydraulic equipment or other expensive machinery. The trend in sampling is toward the use of such labor-saving machines instead of the rocker and other hand-operated devices described above. Additional machines, some of them nnicli different in design from tliose mentioned below, have been described in the California Journal of Mines and Geology. Bodinfion Manufacturing Company, 2401 Baysliore Boulevard, San Francisco, California, has made, on special order, machines for sampling placer gravels. The following equipment was included: revolving screen 30 inches in diameter by oO inches long })erforated with three- eighths-inch holes; 2-inch or 2Tj-inch heavy duty pump; and 2|-hp., 1400 rpm. Novo single-cylinder gasoline engine. The engine was arranged to drive the other machines through belts, chains, and sprockets. All machines were mounted on a steel frame, and some were mounted on rubber tires to make a two-wheel automobile trailer.

Denver Mechanical Gold Van is made by Denver Equipment Com- pany, 1400 Seventeenth Street, Denver, Colorado. This machine has -a motion somewhat similar to that used in hand-panning, imparted by an eccentric which makes 240 coniplete oscillations per minute. Power for both the eccentric and a pump to furnish water is supplied by a gasoline engine of :t-hp. Gravel is placed in a hopper 2i feet above the base of the machine and passes over an upper screen with water from a spray-pipe. The upper screen is a heavy punched plate which passes -inch material. The hopper is provided with a lip to hold back large nuggets. The -inch material passing through the coarse screen goes to a fine screen below, and fine sizes pass through to three concen- trating pans below. The top pan is of copper and is used to amalgamate fine gold with quicksilver. Overflow passes to the two lower pans, which are provided with rubber mats covered with heavy wire screen of 1-inch mesh to act as ritfles. Manufacturers state that the machine is very efficient in recovering both coai'se and fine gold. Capacity of a single machine is to 2 cubic jards bank run per hour. The manu- facturer supplies small tronnnels to mount over- either one or two of the mechanical pans. Capacity of the duplex' pan plus trommel is stated to be 4 to 6 yards per hour.

Denver Trommel-Jig Unit is ma-de by Denver Equipment Company, 1400-17th Street, Denver, Colorado. A trommel, jig, gasoline engine, and pump are provided. The trommel contains a scrubber-section with spiral lifting blades to disintegrate clay or cemented gravel. Rated capacities of three diff'erent models range from 2 to 6 cubic yards bank run per hour. The jigs are 8 by 12 inches or 12 by 18 inches and engines are 3 hp. or 4 hp. All machines are mounted on steel frames. As a sparate unit, an amalgamation barrel is available for amalgamat- ing the gold in the jig-concentrate.

Laizure, C. McK., Elementary placer mining in California, special machines and processes : California Jour. Mines and Geology, vol. 30, pp. 136-227, 1934.

:V>

OK (iOM) IN CAMFORNIA

Bull. 135

Sec. I

Siall-Scale Methods

Fig. 9. Denver Mecii

iinmel. Photo hij

G-B Portable Placer Machine is furnished by The Mine and Smelter Supply Company, Denver, Cohu-ado. It consists of a hopper, combined scrubber and revolving screen, and molded rubber riffles, Avhicli are vibrated at 200 strokes per minute. Tanks are provided for re-use of Avater, but 60 to 75 gallons of water per cubic yard of gravel are dis- charged Avith the tailing, and that amount of make-up Avater must be provided. Rated capacity on ordinary gravel tliat contains little clay and is not cemented is about 2 cubic yards per hour. Power is furnished by a lo-hp. gasoline engine, which drives the scrubber-trommel, pump, and riffles.

Further details about all of the above machines are available from the manufacturers.

34 PLACER MIN'INO FOR GOLD IN CALIFORNIA [Bull. 135

Dragline Dredging

The importance of drajline dmlginff in California is brou?ht out by table 1, which applies to dragline dredging exclusively. It shows the increasing importance of production from dragline dredges for pre-war years. The sharp decline in 1942 was caused by war condi- tions. Not oidy did the War Production Board prohibit gold mining except in si)ecial cases, but ])riictically all of the draglines were put on war work both as oxcaVators and as cranes. Manufacturers of drag- line excavators nnist have time to replace these machines before drag- line dreiiging can be resumed on a large scale after the war. The method was in an early stage of development in IdXi, but the niachinery and niethods were rai)idlv improved, .so that gross production rose to a peak of nearly $8,()0(),obo in 1941.

The name dragline dredge is used in this article to denote a placer mining outfit composed of two separate and distinct units. The dig- ging is done by a standard make of dragline excavator, which travels on the ground by means of caterpillar tracks under its own power. The heavy bucket, which picks up from 1 cubic yard to 3 cubic yards of gravel at one time, is suspended by a steel cable from a structural-steel ,;boom roughly 50 feet in length. Still larger outfits were in use shortly before gold mining was shut down by order of the War Production Board. At the Mocassin mine in Siskiyou County, a dragline excavator of the Monighan type with a 5-ciL yd. bucket Avas in use, and at Uaytou, Nevada, one with a 14-cu. yd. bucket. The one at Dayton did not operate long enough to give a satisfactory demonstration of the per- formance of an outfit of this size. Washing of the gravel is accom- plished on the second unit, which is a barge floating iii a pond. For washing out the gold, the barge carries a revolving screen and riffle tables similar to the units used on the bucket-ladder dredges. The dragline excavator digs away at the edge of the pond, which thus advances. To cause the barge to follow, a pull on cables anchored on the shore is all that is needed. The tailing discharged from a belt- conveyor and sand-sluices fills up the pond behind the barge. The dragline dredge has been called a "doodle bug'' by many persons, but this is not considered an appropriate name, aiul it is not used here.

The older type of dredge, on which the digging is done by means of a bucket-elevator comprising a chain of heavy buckets, each of which is connected by a round pin to the next one, will be called here a bucket- ladder dredge. The ladder is the heavy structural steel member that supports the bucket-chain. This type of dredge is described in a later chapter, Bucket-Line Dredging.

It is not the purpose of this article to indicate that the dragline dredge is in any way superior to the bucket-ladder dredge. The drag- liiu' dredge has oi)ened up a new field to dredging, namely those deposits that are too small to justify the construction of a bucket-ladder dredge. If a deposit is large enough and contains enough gold to amortize the capital investment in a large bucket-ladder dredge, and return a suit- able profit, possibly a dragline dredge should not be considered. How- ever, the large sizes of dragline dredges are considered by some opera- tors to be at least as good as the smaller bucket-ladder dredges.

Bucket -ladder dredges have been made jiortable to a certain extent, and may be used on more than one deposit, but the dragline has the

Division Of Mines

Bui-L. 135. Plate

n.Ah4 View

m

See. I] DRACILINK DREDGING 35

Tabic 1. (lohl piofhiriion from (Ira</linc drrdiics, 103.1-1!) '/.l

Mines

WashiiiK

Cubic yards

Gold recovered

producing

plants

washed

Fine

Vahie

Avei'age per cu. yd.

(iunces

19.S3

1 1 ,500

Si, 924

$0,167

604,000

3,466

121,138

um

3,900,000

22,191

770,701

2(>

10,010,000

49,9()8

l,748,80i

19,304,000

94,142

3,294,970

G8

24,560,000

118,108

4.133,780

31,618,000

172,519

0,038,165

lOG

42,747,000

205,181

7,181,335

45,579,000

225,019

7,875,665

24,52().000

117,900

4,126,710

3,180,000

14,190

496,860

Extracted from Merrill, C. W., and Oaylord, TI. M., Gold, silver, copper, lead, and zinc in California: U. S. Bur. Mines, Minerals Yearbook, Review of 1040, p. 219. See also preprints for 1941, 1942, and 1943.

advantage in tliis regard. The operating cost per cubic yard is roughly the same on the smallest bucket-ladder dredges as it is on the largest dragline.

The dragline dredge has the following disadvantages:

1. The nsnal depth to Avhich they have worked in California is roughly 20 feet. This can be extended somewhat with the largest dragline excavators with ver,y long booms such as the one at the JNIofcasin mine in Siskiyou County described later in this bulletin.

2. The}' will not dig gravel that is hard and compact or partly cemented as well as a bucket-ladder dredge.

3. Bedrock must be soft. No dredge is successful where bedrock is very hard and irregular, but a bucket-ladder dredge will dig harder rock than a dragline.

Subject to favorable conditions regarding depth, ease of digging, and soft bedrock, dragline dredges are successful on deposits too small for bucket-ladder dredges for the following reasons :

1. Less capital is needed to purchase the dragline excavator and washing-plant.

2. The dragline dredges are smaller and float in very shallow ponds because the heavy digging-machinery is not on the barge.

3. The dragline excavator and the tractor with 'bulldozer' blade, \which is now practically a standard item of equipment, can quickly throw up small dams so that the barge can be placed on various terraces and in small tributaries higher than the main channel. If necessar}-, water for the pond is pumped.

4. When one small deposit has been worked out, the modern outfit with barge of steel-pontoon construction can be quickly moved to another deposit. Such a move involving dismantling and re-erection has actually been made in a week's time with the regular crew.

3G PLAPKR MINING FOR GOLD IN CALIFORNIA [Bull. 135

Lopan* and Mapee have written articles on dragline dredges. Since those articles were written, washing plants have been improved, larger nnits have been pnt in service, and cost per cubic yard has been much reduced.

A few details of the geology of the dragline field southwest of Red- ding will be given because conditions are nearly ideal for this type of dredging. Gravels being dredged (1940) are in the channels of present streams and on low terraces adjacent to the present channels. The gravel is seldom more than 10 feet in depth, and most of it is loose enough so that it is not difficult to dig.

Ieneath the gravels of the present streams are sediments of Ter- tiary and Cretaceous age, all of which form soft bedrock that the drag- line buckets can dig. Several inches to a foot of it are usually taken up to recover gold lying on bedrock. To the west of the Pacific High- way for a distance of 10 to 15 miles, the Tertiary bedrock is a clay-like volcanic tuff dipping below horizontal at small angles to the east. Gravels of the Pleistocene Red Bluif formation overlie the tuff in large areas, and they should not be confused with gravels of present streams. Apparently no concentration of gold occurs in these widespread Red Hiutf gravels. In the vicinity of (Jas Point, the bedrock changes from Tertiary on the east to Cretaceous formations towanl the west. The Cretaceous dips east at a steeper angle, roughly 20. It comprises shales, sandstones and conglomerates in general harder than the Tertiary tutf, but a layer near the top is decompo.sed and is s(ft enough for easy digging.

The gold has no doubt been carried over these sedimentary forma- tions from an origin in the igneous rocks, schists, and older sediments to the north and west. Clear Creek is one of the principal streams and it pa.sses through the French Gulch district, well known for its rich quartz veins. Erosion of these has unquestionably contributed gold to the i)Iacer deposits. In the vicinity of Igo is a deposit of gravel cover- ing many acres to depths reaching 100 feet. It is apiiarently an old terrace of (;iear Creek, now high above the present stream. Part of it has been mined by drifting and hydraulicking. Part of it has not yet been mined. Dry Creek and its tributaries, now (1940) being exten- sively dredged with draglines, dis.sect the old Clear Creek terrace, and gold has been carried out by Dry Creek and over Cretaceous and Ter- tiary bedrock. Hence the ]>lacer gold of Dry Creek is derived lal-gely from an older placer deposit.

Some persons have thought of the Cretaceous conglomerates as a possible so\n-ce of the gold, and it is possible that some of the beds of Cretaceous conglomerate contain gold. However, an examination of tlie boulders in the jilacer deposits shows that many are larger than those found in the conglomerates, and that they have apparently been washed in by streams originating in the i-rneou's rocks and .schists, and in the older Bragdon conglomerate (Carboniferous). The bulk of the gold must have been washed along with them. Quartz veins in the Bragdon conglomerate are gold-bearing at French Gulch.

' ''"K'M'- r' l*'-""'-'" "lining In Ciilifornia with power shovels: CaUfornia Jour. .MIrif.v and GeoloKV. vol. .32, pp. :{7;i-.TT7, l'.t3(i.

Ve'Tgi ' il'iiK-lln.! dredge : Am. Inst. Mln. Eng. Tech. Pub. 757,

Averlll r. v.. 0ild deposits of the RediliriK and Weaverville quadrangle: Cali- fornia .lour. Mines and neolocy, vol. 2;t, pp. .1-7.!. map. 1033.

Hinds. N. K. A . Oeologic formations of the Rc.lding-VVeavorville districts, north- ern California: California .lour. Mines and deology. vol. 29, pp. 77-122, map, 1933.

Sec. I] DRAGLINE DREDGING 37

Dragline Excavators

Dragline excavators of such standard makes as Biicyrus-Erie, Lima, Link Belt, Koehring, Marion, Northwest, P. & H., and Thew-Lorain are in use for dragline dredging. Details of various sizes, speeds and horsepower may be obtained from the manufacturers. Thoenen has tabulated some of these data in Liforination Circular 671)8 of the U. S. lUireau of Mines. Fairly higii digging and swinging speeds are desir- able for this type of work, and hence fairly high horsepower. Most of the draglines in California were equipped with Ij-cu. yd. and 1-cu. yd. buckets, but those of 3 cubic yards capacity more recently put in service give a lower operating cost per cubic yard. Some still hirger ones have been used but detailed operating costs on them are not available. Pi-ob- ably additional outfits in these large si/.es will be developed in post-war years. The 1-cu. yd. draglines have 5U-foot booms, and the ;3-cu. yd. draglines have 60-foot booms. Different lengths are obtainable if they are needed to fit different conditions.

Buckets

Both Page and Esco buckets have been used. The Esco with five teeth will dig harder gravel than the Page, but it dumps more slowly. A set of teeth is usually dulled each shift, and must be built up by welding.

Power

The dragline excavator with l-cu.yd. buckets for which cost-data are given below are powered by D-13000 Caterpillar diesel engines rated at a maximum of 130 horsepower. The 3-cu.yd. dragline excavator is powered with a 200-hp. electric motor.

Digging Methods

Two general methods of digging are in use. The common method is to move the dragline excavator in the direction of the channel, and reach to each side as far as possible Avith the boom. Each cut is twice as wide as the horizontal projection of the boom, roughly 60 feet. By utilizing the momentum of the swing, the operator can cast the bucket a little beyond the end of the boom. The other method is to move the dragline excavator across the channe!, tlius placing the caterpillar tracks at right angles to the direction of the digging-cable. Wider cuts are possible with this method, and its advocates state tliat bedrock is cleaned better. This seems rea.sonable, because in the method men- tioned first the arc through which the bucket moves causes a strip of bedrock to remain uncleaned toward the exti-eme reach of the boom. This can be avoided to a certain-extent by overlapping the cuts, but the digging is done under muddy water, and accuracy of this overlap is difficult to attain.

Mats

The dragline excavator can usually ti'avcl on the ground in dry weather, but when the ground is nnuldy or very sandy, mats are needed. These are made by bolting together timbers, about 8 by 10 inches, in sections -i feet wide and somewhat longer than the width of the tread of the dragline excavator. The boom is used as a crane to pick these up behind the caterpillar tracks and put them down in front.

Thoenen, J. R., Sand and gravel excavation, Part I: U. S. Bur. Mines Inf. Circ. 6798, pp. 23-39, 1934.

PLAPEK MIN'IXn FOR GOLD IN CALIFORNIA

[Bull. 135

Fig. 10. Dragline dredge under construction in shop, showing trommel and parts of riffle-sluice.s and staclter-ladder. Photo bii ronrtes}/ of Bodinawi Mannjactur- iiKi Cdiiiixiiiy : reprinted from CdUfornici Joitruiil of Mines and Geology, April ri.ix. p. io>.

Tractors A traetor of tlio cattM-pillar tyjW powered by a diesel engine is now praetically a standard item of ecpiipnient in both drajrline dredging and bucket-ladder dredging. It is usually equipped with a scraper or bulldozer blade in front and often has a winch mounted in back. The ]rincij)al use is for clearing the land of brush and trees. These are either juished or pulled to one side or piled for burning. Many jobs of handling lieavy parts are possible with the tractor, and it is useful in building dams for some locations of the dredge-pond. In dragline dredg- ing, tlie trartor and bulldozer are ])articularly useful for smoothing the way ahead of the dragline excavator, .so that the latter can be moved ahead with a minimum of lo.st time. The tractor and Le Tourneau carryall have been used in a few i)laces to remove several feet of soil overburden containing no gold.

Washing-Plants

The washing-]ilant for a di-agline dredge is mounted on a barge, and consists of a ho])per into which the gravel is dumped by the drag- line, a revolving screen or trommel, and a belt-i;onveyor to stack the coarse tailing behind the barge. Laige streams of water are pumped from tlie pond into both the hopper and the trommel. The sands that pass througli the screen are washed on inclined tables, which are divided by partitions into a number of sluices containing riffles to retain the

Sec. I"

Dragline Dredging

Fig. 11. Hand-winch for dragline dredge. Photo by courtesy of Bodinaon Manufacturing Company; reprinted from California Journal of Mines and Geology, April 1938, p. 103.

gold. The washed sand flows into the pond behind the barge. The following descriptions of details have been generalized somewhat to cover practice in the state, but they are given with the particular plants in mind for which cost-data are tabulated below. The all-steel plants are made by Bodinson Manufacturing Company, 2401 Bayshore Boule- vard, San Francisco. Welded joints are used throughout. Even the corrugated iron housing is tack-welded to the steel frame.

Hulls

The barge for a 14-cu.yd. outfit is 30 feet by 40 feet anil is made of five pontoons, each 8 feet by 30 feet by 42 inches deep. For the 3-cu.yd. outfit, it is 35 feet by 48 feet by 42 inches deep, and comprises six pontoons, each 8 feet by 35 feet. Steel is i\-inch thick, and all seams are electric-welded. Well braced frames for pontoons are made of 2- by 2|- by i- angles. The earlier barges were made of timber frames covered with 3-inch planks, but these are now considered obso- lete and are not used.

PLAf'F.R MINING FOR GOLD IN CALIFORNIA [. 135

I'':g. 12. I'liuer-wiiuh lor ilranHne dredge. I'holo. riiuilfsij ni liodinsDn MdiuiltKl nriny Cii. : II itnntfil III, til CiiUliiriiid JmiiiKil n) .l/iiifs iiiiil Oioloijii, Aiiril lU.iS. 10).

Fig. 13. Trommel for druKline dredge on truck and trailer. Rcin-intcd Jrom Cali- fornia Journal of Mines and Geoloay, April 19S8, p. 105.

Sec. I] DRAGLINE DREDGING 41

Winches

The barge is pulled ahead and swung: to distribute tailing by means of cables anchored ashore and attached to winches on the barge. Hand winches are used on the smaller outfits and power-winches on the larger ones. On a plant serving a 3-cu.yd. electric excavator the winch is driven by a 3-hp. electric motor.

Hopper

A heavy hopper usually made of half -inch steel plates welded together receives the gravel dumped from the dragline bucket. A grizzly of 90-pound steel rails spaced at 16-inch centers prevents large boulders from entering the trommel. An effort is made to lay aside with the dragline any boulders that will not pass through this grizzly. On some washing plants the griz'ly is inclined dowuAvard slightly toward the front of the barge, and boulders are dragged back into the pond with the bucket. Water is discharged from nozzles into the hopper. On the 3-cu.yd. outfit, the hopper is 14 feet by 10 feet and is 13 feet II5 inches above the deck.

Trommels

Details given here are for the plants on which cost-data are given below. Different sizes of holes and different spacing can be used as required by the particular deposit- being worked. For the l-|-cu.yd. outfits, trommels are 24 feet long by 54 inches in diameter. Two end sections of 4 feet eacli are not perforated. Other sections of 4 feet each are perforated as follows: first, f-inch holes with inches of metal between ; second, f -inch holes Avith three-quarters of an inch of metal between; last two, -inch holes and half an inch of metal between. They turn at 14 revolutions per minute. On the 3-eu. yd. outfit, the trommel is 35 feet long by 5 feet in diameter. End sections of 5 feet each are not perforated. The remainder of 25 feet is perforated with -inch holes, but the spacing varies in the 5-foot sections as follows: on the first section inches of metal between holes; second section, -inch ; last three sections, -inch. The different spacing of the holes is to distribute the fine gravel evenly to the riffle-.sluices or tables below. The speed of rotation is 12 rpm. A pipe drilled Avitli f-inch holes extends through the trommel, and water is sprayed from it to wash the gravel.

The intermittent loads dumped into the hopper cause surges of gravel through the screen and sluices. To equalize the flow, some trom- mels have been equipped with an Archimedean screw of one or more turns in the upper blank or scrubber section. This helps to break up lumps of clay and to feed the gravel more evenly into the perforated sections of the trommel.

On the older outfits, the metal housing aroinid the lower half of the trommel ended a few inches above the riffle sluices, and water and sand dropped directly on the riffles. On the Bodinson washing plants, the trommel housing is carried several inches below the level of the riffles into a narrow, depressed steel box running the full length of the trommel. This is provided with baffles or weirs to regulate the flow to the different sluices. It serves also as an effective trap to retain coar.se gold. To recover this at cleanup time, large pipe-plugs in the bottom are unscrewed.

i'i-A( i:h minin<; ion (joi.d in cat.ii 'ohnia IHiill.i:!")

Fio. 14. DraKli

Itrprxntril j.

,1 M,

-:-liii(t s, ininip. atul luimp-srreen. ./ (!roU)<ni. Ainil I'.i.iH, ]i. 106.

Riffle-Tables

On the .'i-LMi.yd. outfit are 10 sluices with riffles on eacli side of tlie tronnuel. Tliey are all ;}0 inelies Avide, are 14 feet lon*r, and eijrht are 1 1 J feet lonjr. They discharge into a jiair of sluices of the same width on each side of the hardie, ruiniin<r len<j:thwise of the bart:e to discharge at the stern. The Jower portions of these sluices are i)rovided with riffles also. In the upper portions, where the sluices running? crosswise of the bar};e disdiai-jre into them, too nnich turbulence exists for riffles to be effective. The trommel and all sluices are set at a j-rade of H inches to a foot. Some desi<>iiers use 1 inches to a foot. On the smaller barp:es for IJ-cu.yd. drajrlines, the arranjrement is tlie same, except that dimen- sions are reduced locoi-respond with those of the barge.

Riffles are of tlie llnufrarian dredire-type of wood, inches deep, 3-iiicli wide, spaced at 1] inches. They are made up in sections of a lenjrth c(|ual to the Vi(lth of the sluice, and about a foot along: the direc- tion of flow. These small sections are easily handled during: the cleanup. The top of the wood is beveled off for an ei<:hth to a quarter of an inch, so that the toj) is nearly level when the riffle is in the sluice. It is shod on top with strai) iron, 1 inch by i-inch, held in place with countersunk wood screws. On the Koarinj; Kiver dredge rubber is substituted for ir<n. But the rubber and the iron are wider than the wood beneath, and overiaj) tlie wood a little on both edjres.

Most operators use expanded metal lath of 1-inch mesh over burlap, coconut mattinpr or En}.disli corduroy in the upper half of the sluices runniiif? cro.s.swise of the barfre, that is just beneath the trommel. The metal lath is raised with t()n<;ne-and-frroove floorinpr so that the top is even with top of the riffles in the lower part of the sluice. Quicksilver is sprinkled on this at the start of each shift, and the metal lath holds the quicksilver do.se to the under side of the flow of sand and water, where it is more effective in amalgamating the gold than in the deeper riffles.

See. I] DRAGLINE DREDGING 43

Wm

Cross Sect/On

Of R/Ffles

O/merrs/ons /n inches

Cross-section of dredRe riffles. Jieprinted jroin CdUfornia Journal of Mines and Geology, April 1VJ8, p. IOC.

Stackers

For stacking: the coarse tailing behind the barpe, the 1-cu.yd. plant is ecjnipped with a belt-eonveyor system, 50 feet long between pulleys, with a 8()-im'h belt. The stacker for the 3-c'U. yd. plant is 50 feet long with a 86-ineh belt. Some of the boats with diesel power have an electric generator and motor so that the .stacker can be driven by the upper pulley. One plant has the upper pulley driven by a shaft running the full length of the stacker.

Power ,

On one of the H-cu.yd. oiitfits for which -data are given below, power is furnished by a D-7700 Caterpillar diesel engine rated at 50 hp. on continuous sustained loads or 63 hp. maximum ; on the other by a D-8800 Caterpillar diesel engine rated at 64 hp. .nd 80 hp. respectively. Electric lights are furnished by 2000-watt Koehler plants.

Power on the 3-cu.yd. outfit is furnished by the following electric motors: 50 hp. on pump, 30 hp. on trommel, 10 hp. on stacker, 3 hp. on winch and 5 hp. on auxiliary pump.

Water

During the first half of the year, for which cost figures are given below, practically all water needed was obtained from the natural flow of the streams. During the dry season.' impounded water bought from a company which furnishes water primarily for irrigation may cost $500 per month total for all three outfits.

Water for washing the gravel on the barges is pumped from the pond on the 1-cu.yd. outfits with a 7-inch centrifugal pump. The 3-cu.yd. plant has a 10-inch pump discharging into the hopper and trommel ; also a 4-inch auxiliary pump to supply additional water to the sluices. The 4-inch pump is used to furnish water for cleaning up the riffles. The proportion of water and sand is variable according to the character of the ground being mined. The mixture of sand and water discharged at the stern of the barge is roughly 10 to 15 percent solids.

PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Fig. lU. Diiieliiie iln-dge under constriu-tinn in (iiki. ICr/nintfil jrom Cali/oritia Jounidl of Mines and Gcoloyy. April lU.is. p. itn.

Sec. T] DRAOMNE DREDGINQ 45

Delays

The plants are kept in operation 24 hours per day. "Operating? hours" listed below include only that time in which the dragline was difrprinj; fjravel and deliverin<j: it to the h()pi)er on the barpje. All other time is counted as delays. These include time for moving:, for lubricating and servicinji" the di'ajiline and other machinery, and for repairs and cleanups.

For a move to a lunv location involvinji.- dismantling of cfjuipment, 7 days are required for the H-cu.yd. outfit, and 8 days for the 3-cu.yd, outfit. The regular crew of rouddy 14 men is used in eitlier case. As extensive replacements of worn i)arts are usually made at this time, an accurate estimate of the cost of siuth a move is not available. Parts and cost of installin*; them should be chai'fied to maintenance and not to movin<r. In such a move the dra<iline is used as a crane to pick up a pontoon or otlier heavy part and load it on a truck and trailer. It is interesting- to note that $1 ,()()() should be ample to cover the cost of dismantling; and re-erection when the len<:th of the truck-haul is moderate.

Merrill in Peele's Mininp: Engineers' Handbook gives a table of actual costs of six such moves ranging from .$1,470 to $1,656. Transpor- tatio)i, partly by truck and partly by rail, was the largest item in each case, and ranged in cost from $900 to $1 ,200. Distances ranged from 50 to 300 miles.

Cleanups

Cleanups are probably made on the average of about once a week. Some operators could no doubt improve their recovery by watching the condition of the riffles more closely and cleaning up when the riffles are loaded instead of at regular intervals. One operator who uses expanded metal lath over burlap near the trommel cleans up the lath after every 80 hours of running time, and makes 80 to 90 percent of his total recovery in this way. The metal lath is taken up, then the concentrate on the burlap is hosed off into a tub. To clean it thoroughly, it is finally held in a vertical position over the tub and hosed again. When the Hun- j?arian riffles are cleaned up, the sections about a foot in length are taken up one at a time, and lighter sands are washed overboard with a hose. Amalgam and several tubs full of the heavier sands are saved for further treatment. This treatment varies with different operators, and ]ouff toms, tables of the AVilfley type, and amalgamation-barrels are all in use. Amalgam is squeezed and ivtortcd, and the resulting sponge-gold is ready for the mint.

One operator who recovei's platinum makes the final concentration by panning, dries the concentrate, and blo-ws away the last of the sand. The metal is then treated with idti-ic acid, washed and dried, and sold to platiniun-buyers.

The c-rew employed on the three outfits for which cost-data are given below comprises the following : 18 men on barges, 9 on draglines, 3 oilers, 3 tractor-di'ivers, 3 mechanic-weldei's, 3 extras used as truckdrivers, etc.,

sMerrin, Charles Wliite, Di-agline dredpiiiK, in Peele, Robert (editor), Mining engineers' handbook, Vol. I, sc. m, pp. ijoO-tlOO, New York, John Wiley & Son.s, Inc.,

I'LAcr.R MIXINCl FOR flor-O IN' fAT.II'OFiNIA

[r.uii. in.')

1 —

F

m-

m

F'lG. IS. DraKline ilr.dK'- to aoonimodat.- IJ-cii. yd. ex.iva tci-. I'luiti, b/i lOurtruM of liixUiiaou MdintJtutHriuii f'ompauy ; reprinted from Cdliforiiid .Imn-nul of Miu'fH (iiul Geolofni. April lllSK. ll.i.

uiif clciiiiiii) iiiaii. and owv siiptM-iiilciidt'iit. Tliis crew ol' 41 iiUMi operates thcllircc plains for 24 liom-s per day.

Capital Investment

The followiiir fijriires ai'c iiiteiidcd lo iiive a roii<ili idea ol" tlie cost of llie pi-iiicipal items of ('(piipnieiit of liijli (piality and l)oii<ilit new about 1

Jl-iu.yd. .i-vii.ijil.

'diesel electric

nnicli xnivalor $21>,(KM) $;{(),(KM)

ItiuK.- .iii'l w!ishiii plant 2(.()0(> :iS,(HM

Ul7 ("iilripijhir tiiKtor, (licsi'j (J.CM)

HIN Ciil.Mi.ili.u- ti-jKti.r, (li.'M-l S,(MM)

Alliuliiii.-nls fur tractor ( iMiJldo/.r-r, wiiiclK Wm

Mis<rllaii'<)iis wcMiiiK, iMc 1,-,(M) 1,7(M>

$50,(Kk) .$71,(Hm

III addition to tliese main items, tlie followin}; may or may not be needed depending.' on the location and other variable conditions: truck, sliop, camp, slock of spare jjarts. electric j)o\ver line and transformers, storare for diesel fuel. A shop of .some kind is usually ])rovide(l. It nuiy con- tain a part or all of tiie followinjr : welding- e(piipment. machiiu' tools. retort for anuil;ram. macliincry foi- (leanin<;- sands, and possibly for recovery of platinum.

Operating Costs

The following firures on operatinjr costs, coverinjr tlie first six montiis of 1I>:{7. were furnished by the auditor of an experienced opera- tor who had been in the l)usiness for some time. All of the ecpiipment was boujrht new for the purpose of dra<rliiie dredjrinjr and liad been in operation for an averajre of about a year before January 1, 19;{7, when the period covered below starts. Depreciation of $1,000 per month on

See. I] DRAGLINE DREDGING 47

each outfit is clmi-'rod by the ojiorator Avitli tlio idea in mind lliat tlie machinery runs continuously, as near 24 hours i)er day as jiossible, not intermittently like e(|uipnieiit used by a contractor. Tlie fijrures are believed to be accurate, but Avith less accuracy in the fijrure for cubic yards than in the others. Yarda<:e uas calculated on the basis of an actual survey for area, but depths Averc estimated. Emphasis is again placed on the fact that this dredginji' -was done under conditions practi- cally ideal for a drajrline. Depth of jiravel was less than 20 feet, it \vas recent jrravel of present streams, loose and easy to dip-; bedrock was soft, and a foot of it was easily du<i- by the dragline ; the outfits Avei-e operated for periods of a year and more on tlie same dejiosits, and no time was lost in dismantling for moves; freezing of water during winter was so slight that it caused no trouble. The only condition not ideal was the presence of growing trees and brush on much of the land. Cost of removing this is included in the same account as repairs. "Wages were $1.00 per hour for dragline operators and $0,625 for other classes of labor during the period.

The lower cost per cubic yard for the 3-cu.yd. electric is due chiefly to the fact that a much larger yardage is handled by the same size of crew as is used on the smaller outfits. The cost per cubic j-ard for power is a fraction of a cent lower on the electric.

Ih-cu.Jid. Ih-cu.yd. 3-cu.yd.

diesel die.sel electric

Gravel bandied, cubic yards 394,050 3.30,000 690,000

Cost of Operation

Dragline, payroll ?4.0o9.10 $4,003.38 .$4,269.20

Fuel oil, lubricating oil, frasoline 1,.-.00.00 1,471.38 57.03

Maintenance 1.405.58 1.204.15 889.96

Cable 592.73 777.03 1,394.97

Direct expense 8,157.41 7,515.94 6,611.16

Washing-plant, payroll 5,283.11 4,489.94 6,307.50

Fuel oil. gasoline 1.2.55.00 1,278.68 160.39

Maintenance 877.22 825.73 949.48

Direct expense 7,415.-33 6,594.35

General operation

Power 3,599.13

Water 159.00

Repair, labor and niatoriaI.><, including clear- ing of land with tractors 8.282.11 7,6.58.11 8,301.89

Compensation insurance 586.70 593.26 585.62

8,868.81 8,251.37 12,645.64

Office, taxes, general 1,001.00 875.39 948.80

Depreciation 6.000.00 6,000.00 6,000.00

Total operating expen.se, 6 months .$3 1,442.. 55 .'?29,237.05 $33,622.97

Cost per cubic yard 0.08 0.088 0.048

Operating hours 2,175 2,489 2,686

No land-costs and no royaltios arc included in these figures.

48 PLACKR MIXING FOR GOLD IX CALIFORXIA [Bull. 135

(lardiicr iiiid Allsiiiaii <rivo a table of costs at 21 i)lai-cr mines with Hoatinjr wasliiM<r plants, but few details of methods of aecountinj>' used to arrive at the fijrures are jriven. The ranjre for most of the plants is y cents to I'J cents per cubic yard. Depreciation is incliuled in most cases, but not royalties. They state that when all costs except royalties are included. 12 cents would probably be about avera<re. Royalties usually are 10 to lo percent of the i-ccovered old. However, some operators bourht the land and reduced this cost. Most of the draglines covered by this table had buckets of 1 1 oi- 1 cubic yards capacity.

"(Iiinlii.T, II., aii.l Allsniaii. V. T., 1'o\v.t-s1i,.v.1 aii.l iliaKliiK' phu-.-r iniMiiiK: V. .S. Uiir. .Mints Inf. ("ire. Toi:!. pp. tU-0,"j, l".t3s.

Dry-Land Dredges

Durinji: the early lOMO's a number of the so-called 'dry-land' dredges Avere built in northern California. Most of them were so poorly designed and constructed that they had no chance to succeed, and were used for very short periods. Even the best of them were built on timber skids to be pulled forward by the power shovel. Gravel accumulated under the skids, irregular bedrock interfered, and much time was lost in moving. Another common fault Avas tailing-sluices on trestles, Avhich needed rebuilding every time a move was made. Lack of head-room often resulted in the tailing backing up against the rear encl of the washing plant. Most of tliese outfits Avere built of second-hand material includ- ing second-hand gasoline engines. Contrast these Avith the latest drag- line dredges, which Avere built of ncAv material of excellent quality, and Avhich AA'ere poAA-ered by diesel engines or electric motors. Gasoline engines may be considered obsolete for such service. Diesel engines soon pay for themselves in fuel-savings.

A fcAv outfits of later design Avere operated Avith some degree of suc- cess, such as the one used by Pantle Bros., in the Lincoln district, Placer County. The outfit included a movable land plant, not self propelled, consisting of a hopper, trommel, centrifugal boAvls and stacker. It Avas mounted on a steel frame supported at the rear on caterpillar treads 5 feet long, and at the front on 8-inch steel AA'heels. The gage AA-as 12 feet and the distance from front to rear axle AAas 14 feet. The gravel AA-as charged to a 3-cu.yd. hopper and Avas hand-fed to a 4 by 10-feet trommel. The trommel consisted of tAvo screens, one inside the other. The inner trommel Avas perforated Avith ]-inch holes for a length of feet. The outer screen AA-as 6 feet in diameter and AA-as perforated for a length of 4 feet Avith 1- by -inch slots, and for a length of 2 feet Avith 1- by -inch slots. The undersize from the trommel Avas distributed to four 36-inch Ainlay centrifugal gold savers running at 100 rpm. The 48-foot stacker, AA'ith an 18-inch belt, AA-hich could be SAvung laterally by hand or raised and loAvered Avith block and tackle, Avas provided for dis- charge of the coarse tailing. PoAver Avas provided by a 35-hp. electric motor,. and a 2-hp. motor on the stacker. The entire outfit Aveighed 15 to 16 tons. It AA-as fed by a 1-cu. yd. dragline excavator.

Humphreys Gold Corporation built some very large machines of this type at Clear Creek, Colorado, and Virginia City, Montana, and operated them successfully. The one at Clear Creek, Colorado, AA-as self- propelled by a 90-hp. gasoline engine and AA-as mounted on the chassis of a craAvler crane. The one at Virginia City, Montana, AAas a huge machine weighing 500 tons. It Avas mounted on tAA'o tractor cha.ssis, and a third set of caterpillar treads. It was self-propelled by 2 motors, each driving one of the tractor chassis. The gravel Avas dug Avith tAvo 2|-cu.yd. 100-hp. electric draglines, and an auxiliary l-cu.-ycl. poAver shovel AA-as used to clean bedrock.

Costs, excluslA-e of depreciation and royalty, of the outfit at Clear Creek, Colorado are giA*en by Gardner and Allsman as $0.25 per cubic yard ; at Virginia City, Montana, as $0.] 183 per cubic yard.

1 Gardner, E. D., and Allsman, P. T., Power-shovel and dragline placer mining: U. S. Bur. Mines, Inf. Circ. 7013, p. 65, 1938.

(49)

Placer Mtnino For 001,0' In California

[Bull. 135

...uii,i (roiii (,...,...,...; ./.,.;; iid/ of Miiirs ntul Grologv,

JUItlKH 1/ I'.l it, I).

The same corporation had one of these larjje outfits in California, but (lurinjj their last prold inininfr in California this vas idle and they were nsinjr the tloatinfj washing: plants such as are described under the headinj; of dragline dredfrinjr in the precedinj: chapter.

These washing plants that are designed to operate on dry ground have not yet been standardized as well as the floatiuf? washinji' plant. They are more subject to mechanical trouble and lose more time on account of bofrprinpr down, which results in a hijrher cost per cubic yard.

Another somewhat similar method of handling: placer gravel is haul- ing it with trucks to a stationary washing plant, consisting of a hopper, trommel, and riffle-sluices for recovering the gold. The oversize from the trommel is usually discharged into a bin, from which it must be hauled away with trucks.

Wni. Von der Ilellen had a successful oi)eration of this kind on MeConnell Bar on the Klamath River, Siskiyou County, 6 miles west of U. S. Highway flJ). The washing plant and trucks handled 1200 cubic yards per day, at an estimated cost of $0.:}5 per cubic yard, exclusive of depreciation and royalties. Gravel was excavated from a pit 40 feet deep below river level by means of a 1-cu.yd. gasoline shovel of the dipper-stick type. The large amount of handling in trucks is chiefly responsible for the high cost.

This method can be used if the gravel is too tight to dig with a dragline or if other conditions are unfavorable to the use of a dragline, but the co.st is so high that the gold content of the gravel must be much higher than that needed for dragline dredging; otherwise the method will not pay.

Bucket-Line Dredging

By Chahi.ks M. Romanowitz* and A. Sawin**

Successful bucket-line dredgriiifr in California, as known today, is an industry of nearly 50 years standing. I)urin< that long period, it has, on the Avhole, demonstrated soundness and resourcefulness. Prin- ciples today are no different from those applying when dredges of 1898 to 1906 were being designed and built. Placer gravel containing gold, platinum, or other mineral products, recoverable by dredging, must (1) be dug, (2) be screened, (3) be washed and the metal saved, (4) be dis- posed of to rock and sand tailings. Thus are set up the primary problems; how they have been met is a story of constant improvement in materials, methods and operating 'know how.' What once was con- sidered impossible often has been accomplished. What may look to be insurmountable today, in dredging practice, probably will be done in the future. Early dredges weighed a hundred tons or less. Today's great dredges weigh as much as 3,750 tons. The digging ladder and bucket line on a large dredge might weigh 1000 tons. The investment for a dredge alone, without property or rovaltv costs, can run from $100,000.00 to over $1,000,000.00.

Successful dredging is not entirely mechanical; it involves good judgment by owners and operators. A dredge might be operated profit- ably in one area, but if moved to another, without redesigning or rebuild- ing to meet new conditions, be a complete failure. Many inexperienced investors hesitate to spend a comparatively small amount of money for prospecting. One feature of placer dredging not common to many forms of mining, is the relative simplicity of proving property value, extent, and characteristics. Long experience with drilling and shafting has developed methods for logging and mapping a gold placer property which make it possible to design a dredge best suited to that property. The presence of boulders, cemented gravel, unusually hard bedrock or other serious conditions can be discovered before a dredge is ordered. Depth of deposit and variations in bedrock elevations dictate the digging ladder length which will work to best advantage. These are physical characteri.stics to be considered ; there are other obstacles, which must be understood, such as local ordinances requiring resoiling or leveling or prohibiting dredging under zoning restrictions. Stream pollution laws will influence the type of tailings disposal equipment needed. Pond water sometimes must be lowered or changed by pumping and plans made accordingly. These remarks only briefly touch upon the many problems in dredging : the thought behind them to suggest careful consideration by anyone planning to dredge placer gravel and full investigation by a competent engineer with a background of dredging experience.

Gold dredging in California first was attempted as farly as Septem- ber 1850 when the small river boat 'Phenix' was fitted out as a dredge and attempts made to mine placer gold from river gravel about 9 miles above Marysville in the Yuba River. According to newspaper accounts of the day, the dredging principle Avas similar to that now in use. An endless chain of scoops brought the mud from the river bottom up to

Director of Sales, Yuba Manufacturing Company, San Francisco, California. Sales Engineer, Yuba Manufacturing Company, San Francisco, California.

(51)

r,2 I'LACKK MININ<I TOK COI.D IN" fALIFORNIA [Bull.l:!-")

a rofkcr-waslicr wliidi was pi-oiM-llt'd In tlic same power (.peratiii? the scoops. Screens separated the fine material fr(mi the coarse and the Pheiiix' was e(piii>ped with a Tiojiardus Patent Anialraniator' wliicli caiifrlit t'recur(ld by the iiseof (inicksilver.

.1. Wesh'v .Jones, in an article entitled ./o/u.s' I'd iitoscojjc of Cali- fornin. described the ' I'henix 'as follows:

"The 'IMu'ni.v' di-cdin;: machine is seen in the Vnl)a River, a cnm- hr<ns arran:ement. by which it was desig-iu'd to dra' nj) sand from the bed (f the river, and obtain jiold in larre (piantities. Tt was soon found, however, that this machine dredfed more money from tiie i)ockets of the owners than it did 'old from the bed of the Vnba. and this kind of di-edjrin' was very sooji aban(h)ne(l. "

Today, technically minded travelers in the dred<iinjr areas of Cali- foi-nia learn that a modern dredfie is a marvel of meclianical efficiency, and while according; to ]\Ir. .Jones, it was a method of minin*r "soon aban(h)ned." he, of cnni'se, had no way of visualizin<r 20th Century (lre(l<.'in<r which be;ian in the Oi-oville area in l.'DB and lias continued snccessfnily thronjili the yeai-s to become a ]n-inci]ial soni'ce of ("alifor- nia's<rold pi-odnction.

Today, two mannnoth dredjies in California excavate jrravel 112 feet and 124 feet respectively below water level ajrainst banks 50 feet or more liifrh. In other words. jrold-bearinjr pravels 180 feet below ground level, laid down centui'ies, jierhaps ajzes, ajo by ancient rivers, are beinpr dredred and today contribute to the welfai-e of the connnunity. state and nation. I)i-ed<res like these represent an investment well over $1,000.- 000.00 each. Thousands of men are emjdoyed. both directly in operation and in maintenance and manufacture. Ii-edjies are <:reat cons\uners of cajntal jroods, steel jrodncts especially. Electric power is a lar<e item of (pei-ating exiiense which indii-ectly snp))orts many men and their families. Lubricatinjr greases and oils are used by the carloads. Rub- ber belts, electric motors, cables and sui)plies of all kinds find constant use in dredging. Quicksilver, for saving gold in riffles, is used over and over again but eventually must be rejilaced and dredges ]irovide a constant market for (piieksilver producers..

It is rather startling to come across a dredge working in a field. Fnmi a distance, it is not always jiossible to see the pond that it digs and which moves along with the dredge. Constantly excavating, digesting the gravel. sa\ing gold, and slacking tailings astern; these nu>chanical 'gold-diggers' operate 24 lioui-s a day. )i'diiuii-ily, an oi)erating crew consists of three or four men ])ei- shift with three shifts per day. A dredgemaster is in full charge ami ])lans his work to comply with the owner's instructions. Average actual i-unning time is better than '22 liours for three shifts. It is only by steady and constant operation that gold dredging can be made to pay. Only l)y handling a tremendous yardage and by operating constantly can returns justify dredging. Since dredging started in California, the average value of ground dredged is less than 12 cents per cubic yard or in other words, about 7J cents per ton. The greater portion of California land dredge<l is of no value for other purposes except possibly for a few weeks gi-azing in the spring. Agriculturally-minded peoi>le raise the cry periodically that good land is being destroyed but they overlook the fact that Avhen land is of more

"Jones. J. We.sley. Jdiu-.s' panto.scope of CaUfornia : a 'lecture' together with pencil sketches depleting the journey acro.s.s the plains to California, section third: California Hist. Quart., vol. p. 24, 1927.

See. I] iu(Ki;t-m\i: DKKiHiixc;— ROMANowri'z and sawin

value for luiiiiii;' lliaii i1 is i'oi- a;ji-i(Milhii'(", mining' must, be jziven prefer- oiU'O. Tliis is tnu' not only in old niiiiiiij:' hut in other branches of tlie industry. One faet often ovei-h)oke(l is that, in California, lliere are approximately 4.()()(), ()()() acres of so-calhd arab hind, nntided. and ])otential dred<:in<i' huid is oid\- a smaM fraction of 1 ])crcent of liiis lare acreage. l)red<in- oi)eratious ret urn to the owners of the hind dredged, in royalty payments, far moi-e than the land could eai-n if planted. The owner's royalty properly invested will pay dividends 'greater than the land Avonhl earn it"crop])ed.

Dredin' lands are found a<l.iaceiit Mo mountain ranges and have been formed in i)ast aiies throii.uh t!te action of streams or glacial iee (hpositin- <:ravel bearing- reconcent rated values. The California ])hicei-s were foi-med by streams cuttinu:' throuuli beds of ancient sti-eams, several of -vvhicli flowed at i-iht anjiles to <he i)res<Mit stream courses. In this manner, ori:inal (h'posits of phicei- uold were reconcentrat(Ml and deposited in sufficient (|uantities to mak-e placer drediu' ])rofital)l(\ Tlie value pei- yard, as stated aboxc. is not hi.iili but occasionally jiroii- ei'ties ai-e found where ])lacer old deposits raniie from HiO-'-O ppi" cubic yard upward. Mncli of the iold is (piite fine and some jiold lias been )-ecovered wliicli would ])ass tlirouizh a screen of ."OO-mesh size. Closer to the footliills, tlie <i-ol(l is moi-e coarse and naturally, as one <iets into tlie hills, nng''ets are found.

The principle of dredjiin.u' is (piite simple, (iood California ])i'actice is to (li<>' with the maximum depth I'eached Avhile the ladder is at 45" with the water level. Di'<>'in<i- is started at the top of the bank, and as the bucket line moves upward, the di-ede swinprs to the left and ri<iht, pivot in<r about the spud which is at the stern with its ]ioint imbedded in rock tailino's. The spud takes the thrust of di<i'in<i', distributing' the load to the fore-and-aft trusses. Siirin<i-mounted spud keepers help in absorbi)!' shocks and distributing- the load evenly. The side swing.iu<>' is accomplished by port and starboard bow lines which are cari-ied from the UJider water end of the di-.i:in- ladder to shore blocks and back to the bow fairleads on the forward deck, thence to the swin<r-vinch, usually mounted inside the deck house on the starboai'd side. As one drum takes up the line, say, on the port side, the other ]iays out a slack line to star- board. As the swinji' to one side is com]~)leted, the operation is reversed.

Material, after it is du<r, is elevated iu the bucket line to the main h()I)l)er and is cla.ssified in a revolvin<i- screen which discharges oversize tailing's to a rubber stacker belt. These larpe tailiu<:s are stacked iu a pile and form the rock tailinjis which can be seen iu parts of the AVest. These rocks ofteu are used for road buildinji' and other jnirposes after bein' crushed and praded in sejiai-ate plants built for the purpose.

Fines (usually minus i-inch) are dischar<zed through the screen to fiold-saving- tables equi])ped with llun.uarian riffles vitli mercury ti-aj) riffles usually used in the ratio of about 4:1. P'ree f>old readily amal- jiamates with quicksilver and is cleaned up weekly and retorted ashore. There is endless discussion concerning jrold los.ses which occur with the discharpre of fine tailings overboard from tail sluices. On a well- constructed dred<;e, mining- clean placer pold which amalgamates freely, it is possible that losses are less than the cost of additional equipment and labor to prevent them. IIoAvever, in recent years, jijrs of one type or another have been in.stalled on several dredfres, used either as a com- plete recovery system or in conjunction w'ith tables and riffles, either

Plackr Mining For Ooij) In California

[Bull. 135

Hi

3 0)™

c'c4 S

2 S

E 5fE

Sec. I] DUCKET-LINE DREDGING — ROMANOWITZ AND SAWIN 55

ahead or behind jijrs. .Tips are old in minin'r, bnt new developments give them a place in prold dredjrinp-. They have been nsed for tin in the Orient, bnt were a l()M<r time in findinjr favor amonjr gold men. Amal- jiamators and other mechanical devi-es are needed with the ji*?s and extra men are recjnired to operate this department. Ynba Consolidated (Joid Fields' dredjres in California. nsinr riffles for <rold saving for many years, are now being e(|Mi|)ped with modern Ynba jigs of new design and iiigh efficiency. Long tests indicate that improved recovery will jnstify the added investment.

:\rost California di-edges are electrically operated with power con- ducted from conne<-tions on shore througli submarine type cables. Transformers on board step down power to usable voltages, usually 440. Several dredges in California, notably the newer ones OAvned by Natomas Company, convert a-c i)ower to d-c power on board. Bucket lines and other units have d-c motors for a wide range of speed. In barren ground the buckets dump at speeds as high as 40 per minute ; in hard digging the speed can be reduced to a few per minute. The new Natomas dredges were designed and built by Natomas C(mipany engineers. Bow swinging lines and hoisting lines are synchronized Avith the bucket speeds. The company claims many advantages for this type of control. Natomas Company also has been 'jig-minded' for many years. Its new dredges make use of Pan-American and Bendelari jigs as primary- gold savers and riffles for secondary gold saving.

Easy digging gravel once was almost a general condition for Cali- fornia dredges but most of it Avas soon Avorked out. As dredges moved aAvay from river and bench gravels and started to Avork on old channels, much harder digging became the rule. Dredges must dig into bedrock to save rich material lying on it or in crevices. Today's dredges are built to cut and dig into hard bedrock or cemented graA'el. One Yuba dredge in California. oAvned and operated by Carrville Gold Company near Carrville, Trinity Comity, digs at a depth of 50 feet beloAv Avater level using 12-cu.ft. buckets. Its poAver and digging ladder construction, lioAvever, are equivalent to tho.se of a dredge Avith 18-cu.ft. buckets. As the buckets dig the bedrock they are forced into the hard bottom by pres- sure of the digging ladder resting npon the backs of the buckets. This dredge has the hardest digging of any knoAvn successful dredging opera- tion in California. It Avas built upon the site of an earlier dredge of much larger bucket capacity Avhich Avas abandoned because it lacked poAver and strength to operate successfully. Manganese steel chips from the bucket lips are found on the gold saving tables; evidence of the tremendous poAA-er used in cutting into the bedrock.

A recent Yuba development in main drive arrangement provides for the use of tAvo a-c motors mounted just aft of the upper tumbler. The motors are of equal poAA'er and sufficiently synchronized to operate Avith- out trouble. Each motor is connected through V-belts to the pulley shaft and the double drive is typical of dredging practice ; pulley shaft pinions to intermediate gears to bull pinions to main-drive bull gears. The inter- mediates are best if of herringbone type. This type of main drive is used on dredges such as Yuba No. 20 at Jfammonton and Capital No. 4 near Fol.som. each an 18-cu.ft. dredge using two :50()-hp. 440-V motors.

No great change has been made in the revolving screens used on dredges in California. In some foreign fields tAvo or more screens are used sometimes but it is California practice to use but one. Material

PLACKR MINING KOR GOLD IN CALIFORNIA [Bull. 135

Sec. I] BUCKET-LINE DREDGING — ROMANOWITZ AND SAWIN 57

for screen and liner plates has been p:reat]y improved. Early screen plates were of low carbon steel ; later of high carbon steel (.40-.50C) with drilled tapered holes. Cast man<?anese- steel screen plates with cored tapered holes were introduced and improved greatly the life of screen plates. One disadvantage was the cored holes ; many operators preferred that holes be drilled because a closer spacing could be secured. To meet this demand, about 15 years ago experiments were made with U. S. Steel abrasion-resisting steel plates. Today many dredge screens have ARS screen plates which are taper drilled. As the name implies they resist abrasion caused by .sand in the screen ; also, they are hard because of chemical content. Cast manganese-steel plates, where subject to pound- ing by rocks in the screen, 'work harden' and are preferred by some operators. Where no pounding action takes place the life of such plates is not longer than AR8 plates which resist abrasive action. Screen plates have tapered holes so as to pa.ss all small gravel entering. Hole spacing and diameter must be determined by experience to secure best results. Plates in different courses of the screen usually differ in hole diameter and spacing to secure better distribution through the screen to the tables or jigs.

Gold saving table arrangement has undergone much thought and change. Older dredges distributed material, which came through the screen, to athwartship sluices which dumped into fore-and-aft sluices; two or more of the former emptying into one of the latter causing greatly increased volume and greater velocity. Because only a small percentage of the cleanup was found in the fore-and-aft sluices, it was long felt that practically all of the gold VNas caught in the athwartship sluices. Even- tually it was found that such gold as reached the fore-and-aft sluices probably was washed overboard because of the increased volume and resulting greater velocity in those sluices. The old theory that greater table area contributed to larger savings was upset by the new findings. A new practice based on total width of all sluices making up the tables and carrying a controlled volume was substituted. Yuba No. 20 at Hammonton, when designed and built, had tables and sluices based on the new ideas. It and later dredges are arranged so that material from the screen can be conveyed from the upper end to any lower position before reaching the tables. All gold saving is done in athwartship sluices which are fed from head gates in two distributor troughs under the screen and extending aft beyond the lower end of the screen. This new arrange- ment secures a more even accumulation of amalgam and avoids the older system of collecting most gold in a triangular section of forward tables near the upper end of the screen. It is found that even with less table area a much higher efficiency results. Double-banked tables are often used ; the upper about 6 inches above the lower. The top tables are provided with counter-weights to aid in lifting them on hinged supports to make easy access to the lower tables.

An outstanding improvement in dredging equipment concerns the bucket design and method of attaching lips. Over a long period man- ganese steel foundries, making dredge buckets, have worked with dredge designers and operators in improving the shape of buckets to secure clean, fast dumping. In the past 10 years the lips have been improved to secure a firm-locking fit with the buckets and several types of bolted lips have been devised and used. The bolted lip, most widely accepted by the operators, makes use of two vertical bolts to hold the lip in place on the

Im.A< Fr Mining For Gold In Camfornia [. 135

Perry Idlor.

bucket tlie ton<rues oi" the lip snugly fitted into recesses in the inner walls of the bucket. At one time it -was customary to take five or six buckets from the line at each weekly cleanup and send them ashore for relippinj; (riveted). Now a lonjr bucket line can be relipped on the dredge without removal from the line dm-ing a cleanup period of 4 to 8 hours.

As long ago as 19] 2, alloy steels were used on California dredges. As dredge machinery became lai'gcr, stronger bucket pins and sliafts were retjuired but the dianieters could not always be increased. The first full heat of alloy steel sold by a mill to one customer came to Yuba at its old Mary.sville plant in 1912. It was nuide to a specification developed by the comi)any 's metallurgist and from then on bucket pins have been of alloy steels. Today's pins are usually nickel-chromium or nickel-chrom- ium-molybdenum steels carefully forged, machined, and heat treated to develop full strength and wearing qualities. "Wearing plates for upper ttnnblers and idlers are usually of heat-treated forged alloy steels or cast manganese steel. Bucket bushings, which are removable, are of man- ganese steel and it is customary to have bushings of varying thickness to adjust the bucket line assembly as pins, bushings, and bucket back eyes wear. The length of a bucket line must be kept about constant and as "the line wears, three or more buckets may be removed to shorten the line to its proper length.

T.ower tumblers are of cast manganese steel pressed onto alloy steel shafts. Bearing seals of many types liave been tried, all with the intent of reducing wear in the journals by keeping out grit. Ladder rollers and their bearings are of many types and those under water especially are .sealed against intrusion of muddy water. Upper tumblers usually are of the one-piece type in California having the body and shaft cast

Sec. I] BUCKET-LINK DHEnfilNG — ROMANOWITZ AND SAWIN 59

inte<?ral. Wearing: plates are bolted in place and are replaceable to maintain a fairly constant pitch diameter to match the bncket pitch.

Dredfje hills have received much attention hy desifrners; in early days they Avere larfely box-like structures of Avood and later steel and made of a size sufficient to support the di'edjiing machinery. As dredjjes became larprer and heavier it became necessary to fiive a lot of thou<ht to hulls, insurinjr a workable freeboard and stability for the dredjje. Acci- dents to hulls sometimes resulted in flooding; and capsizinp-. causinjr j-reat dama<?e aiul occasioiud loss of life. Modern dredjje hulls are desi<i'ned Avith water-tijiht com])ai"tments usino' every precaution to comply with safety re(|uirements. A more modern development led Yuba Mainifac- turin<r Company in lO.'i.l to experiment with portable ]K)ntoons for hulls. Many Yuba dredges and ])ei'haps others today are e(iuipped with fully portable pontoon hulls which form a series of Avater-ti<:ht ccmipartmcnts, bolted tofjether and havinj;- strenjith equal, at least, to any so-called standard construction. Such hulls are especially adapted to dredfjes which may be moved from one pro])erty to another, thereby making; a hifrh .salvage value. The pontoon system of constructing hulls was put to extensive use by the IT. S. Navy during AVorld AVar TT as reported and pictured in the ]iress and trade journals.

Deep gi-avels in California fields and in other ])arts of the world are being dredged successfully because of tAvo develo])ments of i-ecent years. The Perry Patented liucket Idhn- and the Yida Mud Pumping System are jointly res]ioiisible for the success of such dredging. The Perry Idler is a cyliiulrical device mounted under the digging ladder in a struc- tural steel frame. It supports the bucket line about midAvay in its return trip to the loAver tund)ler. This support balances and divides the caten- ary into tAA'O parts. For di-edges digging 100 feet beloAV Avater level, a Perry Idler is jiositively necessary to insure success. It Avas developed by the late Colonel O. li. Perry, a Avell-knoAvn engineer, Avho had much to do Avith dredging in Califoi-nia and elscAvhei-e over a long period of years. From his experience he recognized the need for such an idler to make deep dredging Avith a bucket line a practicable operation.

Coupled in use Avith a l*erry Idler, deep-digging dredges in Cali- fornia use a Yuba Mud Pumping System. Designed to remove silt and mud from pond bottoms Avhere accumulations reach a depth of 30 feet or more, the system Avas first used on Yuba No. 17 at Ilammonton. A more detailed description of the Peri-y Idler and the Yuba Mud Pumping System Avill be found in another chapter Avhere an article concerning the operation of Yuba Dredge No. 20 is reprinted.

Space does not permit a long discussion of many points of dredge design Avhich need careful attention. The boAv gantry supports the digging ladder. The stern gantry sujiports the stacker. The loads and suspension points must be carefully calculated. The spud used for dig- ging takes the full thrust and its design must be such as to Avithstand tremendous loads Avithout failure. Small dredges today ordinarily use one spud and move ahead and about the pond by shore lines at the boAV and stern. Iarge dredges usually make use of tAVo spuds ; either can be used for digging and both used alternately for .stepping ahead. The stacker belts of rubber are typical of the California-type dredge. Long study by rubber manufacturers has resulted in special belts for dredging service; especially non-skidding types, such as American Rub-

(>0 i'i,A( i;h mininc ioh cold in califohnia [P.iill.l:?o

her Manufacturing' Company's " rii<ilitniii<: Kibbed," Avliicli minimize the tendency of wet rocks to roll backward cau.sinr unnecessary wear on belts, idlers, and other e(|uipment. Kubber also is used in dredrinpr for riffles and sluice liners. Molded solid-rubber i-iffles are used on dred<>:es liavinjr a lon<r operatinjr life and despite the liijh initial cost are economi- cal bcause there is practically no wear caused by the abrasive material c(nstantly tlowin-r over them.

I)re(i;:es in California use and wear out literally hundreds of miles of wire rope, liow lines and ladder suspension lines in particular are l)ou<rht with lenrth of service in mind. These ropes take severe punish- ment and oidy the best quality is advisable. Sjiecial constructions, by wire rope mainifacturcrs, have lengthened the life of such ropes and the experience gained in dredjre woi-k has been of <:reat value in recommend- in? ropes for other services.

In summarizing: it may not be amiss to speculate union the future of dredfre construction. The history of placer dredjiin? is one of con- tinuous improvement. Accidents have occurred in the ])ast and in almost every case have jiointed to an improvement which mijiht avoid a repeti- tion of similar accidents. The hunuiu element is always present ami lapses of memory or attention on the part of a wiiu'hman or other mem- bers of a dredj:e crew can result in disaster. Dred<ires of the future will become more automatic in operation than ever. Trends in dred<,'e desijrn today are toward jrreater dependence on electric controls. These will relieve the winchman, to a large deforce, of responsibility for maxi- mum yardaj?e. high running time, and accidents due to human failings. Control devices will jrovide, automatically, efficient operating si)eeds for maxinnnn yardage under all ground conditions, full use of motor capaci- ties inuler varying loads, and thereby maintain highest possible running time. Some electrical devices now safeguard ma(;hinery against human failure. For instance, a "Lilly control'" on a ladder hoist will prevent a winchman from dropping a ladder too fast, endangering the motor windings and also from raising the ladder too high or droi)ping it too far. Improvements, such as are contemplated above, add to the initial cost but will more than pay for them.selves in the long run.

Dredge operators in California have one great advantage over oper- ators elsewhere in the world. Our dredging areas are not far from main highways and transportation is not a problem. Si)are parts can be secured in California on short notice, since the dredge-building industry centers in the San Francisco Bay area. New ideas can be tried in the field and builders of dredges can easily get back and forth from dredges wliile watching new developments. It is not necessary to experiment at tlie customer's expen.se in a far-otf country and wait months for a report. The success or failure of newly designed e(piipment is soon known to the dredge builder. This fact has helped in making California the cejiter of the j)lacer dredge l)uil(ling industry.

Dredging in California for gold is in line with the State's heritage. California got its fast start toward statehood because of gold mining and all through its history, gold has been a mainstay. There is a theory that basic industries are tho.se which can ojjcrate successfully and .ship their products from the point of production profitably; thus considered, gold dredging is a basic California industry and can continue to be one in the future.

Becker-Hopkins Single-Bucket Dredge

Hv If. A. Sawin

A new type placer dredge, known as the Becker-IIopkins Single- Bucket Dredge, was introduced prior to the war. Its inventors are G. E. Becker and II. II. Hopkins of San Francisco. Yuba Manufacturing Company accuired manufacturing and sales rights under the Becker- IIopkins patent. liecker-IIopkins dredges are 'single-bucket' exca- vators; each dredge being a self-contained floating unit, designed par- ticularly for operation on shallow properties, in limited areas, or in nar- row canyons. Avhere it is impracticable to operate bucket-line dredges or other types of equipment to advantage.

The digging unit of a Becker-IIopkins dredge consists of a bucket, built integral with a sluice-type boom, which conveys dredged material from the bucket to the screen. The dredge operates from a fixed posi- tion on the pond surface, being moored by bow and stern lines. The bucket is dropped vertically at the rear end of the well and a cut made horizontally by pulling the bucket forward into and through the material being dredged. The telescoping boom extends in length automatically, permitting a horizontal bottom cut. When the bucket reaches a point under the bow of the dredge, a latch is released and the bucket is elevated radially to a point where the dredged material slides down the sluice- type boom and is evenly distributed to the screen.

Boulders can be successfully dislodged and in many cases put through the screen and disposed of over the stacker. Boulders too large for the bucket can be brought to the surface and cast aside by use of a tractor, usually available on dredging properties. The ready control, Avhich the operator has of the sluice-type boom, makes it possible for him to slide a boulder into the screen gently ; this avoids wear Avhich might result from dropping heavy boulders at high speeds. Control of the slope of the boom also prevents heavy intermittent overloading of the .screen, even distribution being as.sured because the movement of dredged material down the boom can be accelerated or retarded.

Sales Engineer, Yuba Manufacturing Company, San Francisco, California.

Fio. 2" TJfckcr-IIopkins single-biieket dredge. ( Gl )

ITACFH MiNiNi; idK CALIFORNIA [.THo

Fig. 24. Bucket detail, Becker-Hopkins single-bucket dredge.

Each cut follows the previous cut, until the desired depth has been reached. The horizontal cutting action is controlled, which makes it possible to clean bedrock thoroughly. The dredge is moved to new dig- ging i)ositions on the pond by use of the sidelines, and from its new posi- tion, the digging cycle starts again.

This is a brief description of the digging operations of Becker-IIop- kins Single-Bucket Dredge. The other functions of dredging are similar to tho.se on a bucket-line dredge. Power can be either electric or Diesel engine to suit conditions, and all units are made for easy dismantling, shipping, and re-erection.

The original designers built and ojierated a small unit in California in cooperation with A. R. McCJuire of Fresno. Later, Mr. McGuire was interested in the operation of two such dredges (a 1-cu. j'd. and a 2-cu. yd.) in Alaska prior to the war. Just before the war, Yuba built its first one for use on Butte Creek in Butte County, California. Experi- ments with it demonstrated worth-while qualities but also pointed to several 'bugs' which resulted in design changes to improve its operation. War conditions closed down the work but as this is written (January, 1946) the dredge is being rebuilt on a property in Yuba County and it is planned to operate it experimentally for several months to test the new design.

Jigging Applied To Gold Dredging

r.v 1'. Malozkmofk**

Jijrin<- is one of the oldest processes used by man in separating the heavy minerals from the lijrliter rangue. At the turn of the present century it was extensively used for the concentration of base metal ores and for the washing of coal. Comparatively recently it has been widely applied for treating placer gravels in recovering tin, tungsten, and gem stones.

Its extensive application for the recovery of placer gold is of even more recent origin. One of the earliest large scale jig tests on board a gold dredge was made by J. W. Neill in 1914 on the Yosemite dredge in California. Subsequently, tests were made by the Natomas Consolidated Company, also in California. This company used Neill jigs in fore-and- aft sluices in an effort to effect a saving of some of the gold that was being lost in the tailings.

However, these were isolated examples for some twenty years, until, in 1932. the Bulolo Gold Dredging Company initiated a series of thor- oughgoing tests, as the result of which one of the company's dredges in New Guinea was completely equipped with an installation of Bendelari jigs. This installation proved the practicability- of treating the entire output of the dredge (screen undersize) with jigs, and the companj took steps to prepare for extensive application of jigs on their boats. The company's engineers soon designed a new machine, now- know-n as the Pan-American Placer Jig, in the effort to make a jig particularly adapted for use on board the dredges. Subsequently, several more boats in New Guinea and in Colombia were equipped with jigs of new design. As the result of the success of these installations, interest in jigging on board the dredges was again aroused in the TTnited States, and in 1936-37, instal- lations were made by the Yuba Consolidated Goldfields, Ltd. in Cali- fornia, and by Fisher and Baumhoff in Idaho. Of recent months several other companies are reported to have made jig installations on their dredges.

These efforts may well mark a turn in the history of gold dredging industry, spelling, as they do, the directing of attention towards improv- ing the gold recovery by the elaboration and refinement of the gold saving practices on board the dredges. Not that efforts in this direction were lacking in the past, for great improvements in the design of riffles and their adjustment were made ; but riffles obviously have their metallurgical limitations, especially under the conditions imposed by dredge practice. Jigging, on the other hand, is free of some of these limitations, and, if properly emploj'ed, capable of meeting even the more exacting dredge conditions successfully. Jigging on board the gold dredges is a modern development in dredge practice that no operators can afford to ignore, and one, it seems safe to predict in the light of the interest already aroused, which is destined to gain almost universal application in the very near future.

Now that the groundwork has been laid, and jigs on dredges, when properly installed, have been proven beyond any reasonable doubt to be

Written for and published as pamphlet by Pan-American Engineering Company, 820 Parker Street, Berkeley, California. Printed in condensed form in Engineering and Mining Journal, vol. 13S, no. 9, September 1937. Reprinted by permission of Pan- American Engineering Company.

Formerly metallurgical engineer for Pan-American Engineering Company.

1 Neill, J. W., Application of jigs to gold dredging: Min. and Sol. Press, vol. 109, p. S39, November 2S, 1914.

(63)

G4 TLACKK MINING KOR GOLD IN CALIFORNIA [Bull. 135

botli prufticahle and profitable, tlic time seems propitious to rehearse for tlie benefit of the teclmieal fraternity the advantages that jigging on board the dredges otter, and the problems that will eonfront the operator who contemplates an installation of ji;.'s.

The subject is so vast and its ramifications are so numerous that it would be impossible to deal with it in detail within the scope of a single magazine article. The main imrpose of this paper, then, is to define the problems involved in <rcnci-al tei-ms so as to jn-esent an introduction to a subject that is both timely and little known.

The use of jigs on dredges will be considered only because of their ability to effect a saving of in addition to that made by the riffles. That losses exist when riffles only are employed is recognized by every intelli]L'ent dredge operator; and despite exhaustive efforts towards improving' riffles and other conditions on a dredge, appi'eciable losses are ever j)res('nt in the majority of ca.ses, {ireater in some than in otliers, yet usually of sufflcient nuinitude to warrant serious consideration of some other means of reducing these losses. The gold lost by the riffles is j)red()minantly fine, althou'-h sometimes it might be comparatively coarse if ffat and difficult to amalgamate. The jresence of "rusty" gold in the ground is usually indicative of appreciable losses, for it is a general con- tention amonji: placer o])erators tluit the gold wliich does not amalgamate or anudgamates only with difficulty, such as "rusty gold," is difficult to save by the riffles.

Limitations of the i-iffle as a gold saving device are inherent in it: its action is such that the gold must settle and be entrapped by the riffle in a swift cui-rent of water, the velocity of which must be great enough to transport the material, both coarse and fine, across the riffles. The less the velocity of the current of water, the greater is the tendency of the gold to settle and be saved by the riffles, yet at the same time, the less the carryiu'; power of the water stream; and con.setpiently the yardage cajjacity of a given area of riffles is reduced. Since space on the dredges is limited, only a certain limited riffle area is available for a given yarda<re to be handled by a dredge. In the effort to increase the output of a dredge, the yardage is often boosted beyond the optimum capacity of the available sluices, aiul the amount of water and the slope of the riffles is so rejrulated as to induce sufficient velocity of water to transport all the material; the recovery of the gold will naturally suffer under such conditions. Still other factors, such as packin<; of the riffles, esjiecially with lieavy black sand, and siulden surges in feed which tend to- dislodge aiid wash out the gold that has already been entrapped by the riffles, are all inimical to tiie optinuim recovery of the gold, and can not always be fully corrected.

The action of the jig, on the other hand, disposes of several factors tliat cause loss of rold in the riffles. The jigs operate continuously, and the bed can be adjusted so as to permit settling and, consequently, trai)ping of the gold at all times. Once trapped, it is removed from the stream and there is no more daufrer of losing it as there is in riffles that pack, or from which gold is dislodred and washed out because of occa- sional sur;,'es. The j)icsencc of a larjre amount of black sand in the ground, which causes especially severe packing of the riffles and conse- quent loss of gold, will not cause lo.ss of gold by jigs. Furthermore, dilu- tion of tlie feed to the jirs need not be so great as to the riffles, since in the case of ji};s the transporting' of the nuiterial is aided by the alternate

Soc. J] .ii(:(!iN(! Ai'i'Mi:i) TO (i()r,i) dukixunc; — MAii()Zi:i\r<>i'i' 05

l)ulsati()iis, whereas the earryinj:: power of Avatcr is the sole transporting ajreiicy in the case of riffles. For tliis reason tlie conditions on top of the jifX bed can be made far more (piieseent than for riffles, affording a better opportunity for tlie gold to settle.

Natnrally enough, the jig has its limitations also. It is only a grav- ity machine, therefore will recover only that gold which will settle by gravity under the conditions that obtain on the jig bed. Some of the fin- est gold will be lost by the jigs as well, but at the present stage of develop- ment of the arts of the recovery of gold, this loss is in almost all cases below the economic limits of the known methods.

Plotation, for example, can probably be applied in some form or other for the recovery of the fine gold that \yill be lost even by jigs, but the cost of doing so, it appears at present, will come very close to, or exceed the amount recovered. In 1!);;} an installation of six full size flotation machines, which treated ']()() tons per day, was made on one of the dredges operating on the American River in California.- Three months' opera- tion showed that the recovery of gold by flotation from the sand wheel overflow, which should contain the bulk of the finest gold in the dredge tailings, was only 2 to 5 cents per ton on heads of 3.5 to 9 cents per ton, as calculated from the concentrate and tailing assays. An average of 120 assays made on the flotation heads directly gave a value of only 9.3 cents per ton ; each assay was made on six to eight assay ton charges. These values are based on $35.00 gold.

Besides, it must be remembered that all placer deposits were formed as the result of the material settling by gravity, and in most of the placer deposits now being exploited the finest gold had already been eliminated by natural agencies during the process of deposition, except in rare cases in which the conditions of deposition were such that even the finest material settled and formed the deposit. For this reason there will be very little gold that cannot be recovered by gravity, provided the method of recovery is sufficiently refined to reproduce the settling con- ditions that obtained during the formation of the deposit, when material settled by gravity under natural agencies.

There are, of course, some exceptional deposits in which the gold has been liberated by chemical agencies from the. gold-bearing sulfides, or those in which the gold is still locked up within the sulfides or oxides that have been deposited with the sand and gravel comprising the deposit. Such occurrences of gold present individual problems that involve meth- ods of milling in one form or another for their solution and will not be considered in the present paper.

The use of jigs for the treatment of placer gravels presents problems some of which are entirely different from those encountered in the use of jigs in milling in the concentration of base metal ores. In the base metal ores the ratio of the specific gravities of the valuable mineral to that of the gangue is relatively low; for this reason, and in order that the jigs make proper recoveries, it has been general practice to classify the feed as to size rather closely, and to provide a jigging surface that is much longer than it is wide.

In placer gravels, on the other hand, the ratio of the specific gravities of the gold to that of the sand and gravel to be discarded is very much higher than for base metal ores. Close classification of the feed, though

-A. test made by the Pan-American Engineering Corporation, Ltd.

Gf) vL\n:n minixc ioh cold is CALiroRNiA [Bull. 135

(It'sirablf. is nut so cssi-iit i;il. iior <l'fs llic i-atio of Iciifth to widtli of surfat-o need he so -rcat. Accordin-rly, the load i)er s(|iiaro foot of jip<riii' surface can be niatei-ially increased without ai)precial)ly att'ect- int,' the residts that cau he ohtaiued.

This is fortunate, for wow it not so, jijriuji: as practiced in metal mininj: industry couhi hardly have h(>en ai)plied to the p:old dredfres. Close chissification of the screen undersize on the drede would iu)t be practicahle; and floor space is always at a.preniiuin, thus requirinjr the saving' iuacliin(>ry on hoard the drcdic to have lai'fze capacity ])er unit of floor space.

When attention turned to ji<rs to he used for dredges a <rreat many different desijrns of jijrs u.sed in washinj; of coal and in coiu-entration of hase metal ores were available, but none of them were desi}rned to conform to the altojrether peculiar conditions imposed by the <i:old savin-:' dredjre. For the most jiarf. the jijrs were heavy and cumbersome. occui)yin<;- con- siderably more space than is i-eipiired by the elfective jie-giufi- area. One of the first ji<:s tried out on a <rold di-edpe. the Xeill f)i<i, conformed to the demand for economy of floor spat-e and total room occupied was con- fined to the screen area of the .jijr;zinjr surface.

The first modern jir ap])lied to <rold di-edjj:es was the Bendelari Jifjj, wliich actuated the water throuj.:h the screen and bed from below by means of a ilunjrer sealed with a rubber diaphrajiin. This permitted the floor spac(; to be defined by the screen area of the ji'.

Somewhat later a new ji'/ was desijiiied by the Placer Develojunent Coni|)any's cnjrineers and used with success in New (luinea at the liulolo (ioldfields. In this ji<r. now known as the I'an-Amei-ican Placer Jipr, a jKirf of the hufi-h in tlie form of an iiivei-ted coiu is moved by means of an eccenti-ic to transmit the ])idsations thi-oujih tiie bed. Free discharge of eoiiccjitrates and unifoi-m disti-ibntion of ])ulsation througlumt the area are thus aided. The weight of the machine was cut down to tlie mininnnn to meet the demand of the dredges, especi;dly the smaller ones, for least weight of the gold saving e(juii)ment.

In jirinciple. these modern jigs are no different from the old type machines, such as tlie Ilarz Jig. To secure activation of the bed the water pidsation is transmitted mechanically by means of an eceentrie. In the Harz this was done by a phniger working in a separate water com- partment outside the Initch ; in the Placei- .lig this is done by a moveable cone-shaped hutch, and in the IJendelai-i by a diai)hragm inside the hutch.

Jigs foi" gold ]ilacer operations ai"e designed so as to i)roduce the concentrate continuously as a hutch product. A certain amount of shot bedding is usually used to reduce the amount of concentrate thus obtai?ied. It is (piite inii)ortant to have delicate control over the suction so as to be able to seciu'e maximum recovei-ies with the maximum ratio of concentration. This reipiirement was answered by a Initcli water connection closely coidrollcd by a i)lug cock. A screen area of 42 by 42 incites has become largely standard for the jigs used on dredges.

Testing of Dredge Tailing Losses Eveidually, perhaps, it may be found that all gold dredges that employ riffles .shoidd install jigs to improve the recovery of gold. But because jigging on dredges is a comparatively recent development, and data on wide variety of dredge operations are still lacking, such a gen- eralization is prematm-e. Hence, whenever a jig in.stallation is eontem-

Sec. I] .HGfllXG APl'LIKI) TO GOLD DKKDGINCi MAI.OZi;>[OFF 07

plated, it sliould riglitly be preceded by suitable testing, which can definitely prove that the jigs are capable of eflt'ecting a recovery in addi- tion to that obtained by the ritlles.

The existence of dredge tailing loss may be (jualitatively detected with relative ease, yet to arrive at a definite, reliable figure in cents per yard is an extremely difficult task. The difficulty of this problem will readily become apparent if the factors that complicate such a determi- luition are considered.

The values recoverable by jigging from dredge tailings are usually vei-y low, in the majority of cases less than 5c per yard ; the gold is free and not uniformly distributed; so that even if a very large sample of several tons be taken the sample would hardly be representative of the dredge operation as it is conducted from day to day. Anyone acquainted with the dredging operations is familiar with the fact that the gold usually occurs in the ground in "pay streaks" of comparatively small thickness, and before the "pay streak" is dug a large proportion of the total digging time is consumed in moving material that is barren or nearly barren. Thus, even the most elaborate intermittent sampling will almost always be open to doubt.

However, a quantitative determination of the sluice tailing losses can be made accurately by detei-miiiing the gold content of a small, con- tinuous cut of the total flow of the tailings ; such for example, as con- tinuous jigging of the total flow of one tailing sluice, or of a stream representing a small jart of the total dredge tailing flow.

Numerous methods can be applied for this purpose; a fairly com- prehensive discussion of them and of the interpretation of the results is beyond the scope of the present paper. The subject is sufficiently broad to merit its presentation in a separate, full length paper.

Suffice it here to say, that a reliable determination of the dredge tailing losses is possible, and should be made for the border line cases, in which it appears that the existing loss is small and may not be suffi- cient to justify the use of jigs.

Besides the determination of the amount of gold that can be saved by the jigs, testing may at times be required for other purposes. For example, a special method of treating the rougher concentrates may be found neces.sary, especially when the ground to be dredged contains a large amount of heavy mineral constituents, such as black sand and P3'rite ; or, again, when a part of the gold in the ground is present in the form of included values within the heavy mineral constituents. In these cases large scale testing on the dredge may be necessary in order to be able to devise a suitable method of treating these concentrates for the final recovery of the gold.

Factors Affecting Jig Installation and Jig Recovery

The nuinber of jigs necessary, the manner in which they are installed, and the method of treating the rougher concentrates will depend on a large number of local conditions that will vary widely from one operation to another. A few of the more important ones are : total yardage dug ; proportion of screen undersize to oversize ; ease with which the ground is disintegrated and washed, which in turn may determine the dilution of the feed to the jigs ; the nature of that feed ; and the nature of the gold, i.e., whether coarse or fine, flat or granular.

(is I'I,A( I.K MISINC lOK COM) IN ( AMIOHNIA (r.nll.1.5

Altlu.u'h till' Tin'cliaiiical capafity of a 42 by 42-inch jig has been established at abont :iO cubic yards per hour, the etTect of some of the above factors may necessitate a radical revision of this figure. It needs be reduced for sandy ground, when excessive dilution obtains, or when fine, flat gold is i)resent. At times it may be possible to rate the capacity of the jigs to fit the conditions that obtain when the dredge is digging j)ay gravel, even though they will be overloaded when it is digging the top ground, wliicli may contain a greater proportion of sand than does the pay gravel. As long as this material contains little or no gold no harm will be done.

Excefisive dilution of the screen undersize will usually mean exces- sive top water velocity over the jig bed, and will cause the loss of fine gold that does not have a chance to settle in the swift current. When this excessive dilution cannot be reduced because the ground requires a large amount of water for proper disintegration and washing of the ma- terial in the screen, the jigs should be rated at a lower capacity than nor- mal and some means of controlling the velocity of the top water across the jigs should be provided; boiling boxes or retarding baffles are the usual remedy. Another method to obviate this difficulty is to dewater the entire jig feetl, or some part of it. Although this may not always be jossible, it will always be desirable. Dewatering elevators, dewatering tanks or sumps may seem a revolutionary, complex innovation on a dredge, but it is one that can certainly be justified when jig recovery can thereby be appreciably increased.

After the jigs are properly installed, there is yet their adjustment to make, which is a problem that is at times quite complex. The material passing through the dredge screen from hour to hour is generally variable to the extreme, both as to quantity and character. Since the amount of water added to the screen will usually remain constant, with the variation in the quantity of solids delivered to it, the dilution of the screen under- size will vary in inverse proportion. Because of the variation as to (piantity and dilution, the distribution of the load fore and aft will change con.stantly. Moreover, the list of the boat from side to side, and the pitch fore and aft will att'ect the distribution of load accordingly. These difficulties, more serious on the small dredges than on the large, may be overcome to some extent by a carefully considered installation, and by an adjustment of jig controls that would permit effective jigging even at the worst of conditions. This, however, would only be a com- promise and would never be altogether satisfactory, since under other conditions that would obtain sucli adjustments may not be the optimum. The only etTective remedy for aggravated cases of this sort is the instal- lation of a central distributing system, which would consist of a central, preferably mechanical, distributor, to which the entire ])roduct from the screen is delivered, and from which the load is equally distributed among the several jigs installed on the boat.

Jigging Practice Jigging practice consists of several different operations. The first is the roughing treatment by one row of jigs on each side of the dredge screen. This is usually followed by a second treatment over the scavenger jigs. The scavenger jigs are necessary to assin-e the more complete recovery of the fine gold. Only in special cases will it be possible to limit the operation to a single treatment by one row of jigs : such, for example.

See. II .II(i(iIN(i AI'l'MKO TO (!<)IJ) DKKIKiINC SI \L0'/A:UC)V'V ()9

ill wliic'h only a small proportion of the total f;old in tlie g:round is fine; but wlien the <j:o1(1 to be reeovered is jiredominantly fine, the number of jips installed has to be increased so that each is required to treat con- siderably less than its normal rated capacity.

Besides the roujrhinfr and scavenpinf? some method of treatment of the rougher and scaven<rer concentrates must be provided for. Gen- erally, the feed to the jifrs, depend in; on the size of the dredge, will be from 100 to 400 cubic yards per hour. The ratio of concentration that can be achieved by rougher and scavenger jigs will on the average be 100 :1. This means that from 1 to 4 cubic yards of concentrate per hour must be treated for the recovery of gold. Obviously, this cannot readily be done by batch treatment but must be done continuously.

There are two methods that have been developed for this treatment:

(1) The concentrates may be treated directly for the recovery of gold by grinding in the ball mills in the presence of mercury and then passing the resulting product over amalgamation plates. Grinding need not be very intensive, as the polishing of gold and its ready amalgamation is the main purpose of such treatment.

(2) Another method, which is the simpler and therefore the prefer- able one, is to pass the rougher concentrates over suitable cleaner jigs in order to reduce the amount of the final concentrate to be treated for the recovery of gold. Of recent months a hydraulic jig known as the Pan- American Pulsator Jig, has been used for this purpose to an advantage. It allows the production of a cleaner concentrate that bears a ratio of 1 :30 to 1 :100 to the primary concentrates. The final concentrate is thus reduced to a small bulk that can be readily amalgamated in batches, as in an amalgamating barrel, and the amalgamated product either rejigged or streamed down for the recovery of mercury and the contained amal- gam. With this method, the loss of gold in the intermediate products that are discarded is negligible.

With different combinations of the two methods a large number of variants can be had. For instance : the primary concentrate may first be rejigged, then the resulting cleaner concentrate subjected to continu- ous or intermittent grinding in the presence of mercury, and finally passed over a trap and an amalgamation plate for the recovery of the mercury and amalgam. The obvious advantage of such a procedure over the direct grinding and amalgamation of the primary concentrates is that the size of the grinding installation can be only one-thirtieth to one one-hundredth of that necessary for direct treatment.

Installation

Various methods of applying jigs to existing or proposed dredges may be employed. They can conveniently be grouped into two classes : (1) installing jigs as auxiliary recovery equipment, conforming to the existing sluice layouts ; (2) installing jigs as essential recovery equipment which may or may not entail the elimination of the existing sluices.

When jigs are installed as auxiliary recovery equipment they may be placed either in the fore-and-aft sluices or at the end of the lateral sluices as is shown by the accompanying figures 25a and 25fe, respectively. When in fore-and-aft sluices, as in figure 25a, the jigs will probably be required to take more than their share of the load because the amount of material that these sluices usually handle is greater per inch of width than it is on the lateral tables. Also, because the riffles require more

ri-.\( i:i{ MININC lOK (Kllil) IN CAMFOKNIA [l-5ull.l3o

Hs

-Lateral Sluices

Rougher Jig

Scavenger Jig

m-

FORE t AFT SLUICES

y

9r 1

ii<

8§;

I§

Shh

Km. 25. JiK arrangement.s: four imthods of aiJplyiiiB jigs on gold dredges, o. Jigs instnlled in fore-and-aft sluices; b. jigs installed at end of lateral sluices; c, jig-H in.stalled in lateral sluices, preceded by short .sections of sluice; jigs installed In lateral sluices, next to the screen.

Sec. 11 JIGGING APPI/IED TO GOLD DREDGING — MAIiOZHMOFF 71

Avater tlian is best for jiji'jiinjr there Avill always be excessive dilution impossible to reduce, and consequently, an excessive velocity of top water that will be difticnlt to control, liesides, headroom will be limited at this jioint.

Wlien installed at tlie end of the lateral sluices, as in figure 25&, the load over the jigs will usually not be excessive, as the width of the total jig installation will be equal to the Avidth of the total table area. But here again, excessive dilution and velocity of top water obtain, and headroom is not always available.

Either one of these methods recpiires a double clean up. The sluices ahead of the jigs will recover the major pro])oi'tion of the gold and must be cleaned up every so often ; the jigs will yield an additional amount that is cleaned up continuously aiul therefore separately from the major riffle clean-up.

It would therefore seem preferable to install the jigs as close to the screen as is possible, so that they may constitute the essential recovery equipment. In this location dilution of the feed can be more closely con- trolled, the headroom is almost always available and only a single clean-up is necessary. If riffled sluices are contemplated below the jigs they will have a much better chance of doing good work because the jigs will remove the heavy mineral constituents which are such a source of trouble in packing the riffles. Figures 2.10 and 25c/ show a possible method of installing jigs as essential recovery equipment. The jigs may or may not be preceded by a short section of sluices, the main purpose of which would be to distribute the feed uniformly across the width of the jigs. These short sections of sluice may also be riffled and made to trap out coarse gold and tramp iron. The installation of jigs in this position will not necessarily involve the scrapping of existing sluices, as the jigs may be cut into them.

Although at present the installation of jigs on a dredge will be con- templated only if the jigs can be shown to produce greater recovery of gold than the existing riffles, the time may not be far distant when it may become recognized that the jigs offer sufficient other advantages to be installed even when they do not yield increased recoveries of gold. As mechanical improvements of dredge machinery are made, the percent lost time owing to repairs will decrease, and the periodical clean-ups of the riffles may necessitate loss of operating time in addition to that due to dredge repairs. This obtains even now in a great number of dredge operations. With proper jigging installation it may not be necessary to have any riffles on board the dredges at all, consequently the entire clean-up can be effected continuously, involving no loss of time. There is no reason for the jig repair to be responsible for any appreciable loss of time, since, if properly cared for, they can be made to operate almost Avithout interrujitious. In milling, which employs similar machinery, it is not- unusual to have 98 to 99 percent operating time year in and year out.

This paper is tin- (nit;;ro\vth of some of the work done by the Pan-American Enffineerinj; Compiiiiv at the instance of the Placer Development Company, Ltd., Yuba Consolidated fJold Fields, Ltd., and Fisher and Raumhoff, to which companies credit is due for initiating' the installation of .iijjs on dredges recently. Their cooperation in that work, which made the writing of this paper possible, is gratefully acknowledged. Also, the writer wishes to acknowledge with thanks the helpful guidance given by V. E. Bramming and F. "W. Collins.

.CKK MlNINCi 1-OK OOM) IN CALIFORNIA [Bull. V.\r,

Notes On Jigs For Gold Dredges

By p. W. Collins*

The article Avritten by P. Malozemoff entitled Jigging Applied to Gold Dredging and published in condensed form in Engineering and Mining Journal, vol. 138, no. 9, 1937, is a very well considered paper, and it is reprinted in full above. This paper of Malozemoff 's shows the pic- ture as it was late in 1937, and since then a great deal of detailed informa- tion has been developed that was not then available. High points of these developments are briefly outlined below.

Methods and equipment have been developed for testing tailing from existing dredges to determine the amount of gold present that can be recovered by jigs. Figure 26 shows one of these testing sets. The method is to cut a sample of about 2 cubic yards per hour from one or more tail sluices and this is fed continuously to the 10 by 60-inch rougher-jig. The tailing is measured to determine volume treated and the rough concentrate is jet-pumped through a rubber hose to the dewa- tering cone ahead of the cleaner-jig. The overflow from the cone goes to the pond and the underflow to a 12-inch Pulsator jig. The photo shows a 12-inch single-cell jig, but a two-cell jig is usually used. The cleaner- jig concentrate is amalgamated. A number of dredges have been remod- eled to use jigs after being tested with this equipment and results to date indicate that the test results are reliable.

From 1932 to 1936 the trend was to install jigs as scavengers follow- ing conventional riffled sluices but the error of this is so apparent that now the jigs are being installed as close as possible to the screen and are depended on entirely to save the gold. However, it is desirable to have each rougher-jig followed by a sluice 3 or 4 feet long and as wide as the jig. This sluice should carry burlap under expanded metal and its pur- pose other than carrying the tailing to waste is to act as an indicator of the work being done by the jig. If any gold shows up in the burlap then the dredge master should check up on the jig-operators.

The distribution of the feed to the rougher jigs is of prime impor- tance and this has been worked out in a very satisfactory manner along lines first developed by Natomas Company. The distributor immediately below the screen is made as a modified Jones riffle and automatically makes a 50-50 split of the screen undersize to the two sides of the boat. It may then go directly to the jig opposite its point of exit from the split- ter or be discharged into a fore-and-aft distributor sluice. There is one such distributor sluice on each side of the boat and any material in these sluices may be fed to any jig aft of the point where it enters the sluice. As the major portion of the fine material tends to come through the screen near the forward end, this system permits the fine material to bypass the forward jigs and reach those farther aft that would be 'starved' if their feed carried only that part of the fines that comes through the lower part of the screen.

The attached flow sheet is for a 9-cu. ft. (nominal size) dredge that normally digs about 11,000 cubic yards per day and has dug 13,000 cubic yards in 24 hours on several occasions. The screen openings are half an inch in diameter, and about 50 percent of the bank run is under-

Mechanical Engineer, Pan-American Engineering Company, 820 Parker Street, Berkeley 2, California.

( 73 )

IT.ACKK MIX INC nOI.l TN" CALIFORNIA

[r,ull.l:r)

Fio. 27. liiiUKl

size. The pumping of the rouhei-jiji- coiu-entrate i.s iieeessai-y on this partieiilar boat but can be avoided in some cases. A mechanical dewater- inp: device for the rougher-ji<:: concentrate is more desirable than the settlinjr tank shown on tiie flow sheet.

Placer-type jijzs or similar machines art' always used as roudiers and in such fields as Ilannnonton and Xatomas where the 'black sand load' is comparatively li<rht they may also be used as cleaners but when the deposit to be dreded carries a considerable (juantity of lieavy material the Pulsator jipr should be used for this purpose.

Two systems of recovering: the jrold from the roujrher-jip: concentrate have been develo]ied and are in use on a number of dredjres. The first is to pa.ss the roudicr-jip: concentrate directly to 'aup:er liole' riffles, which amaljramate the clean {rokl. Tails from these riffles are dewatered and fed to a cleaner-ji which makes a tailinj; and a concentrate. The con- centrate fjoes to a small jrrindinp: mill, and it is jireferable to dewater ahead of this mill. The mill-discliare ;oes to another set of 'auger hole' riffles and then over a scavener jijr and to the pond. The scav- enfrer-jig concentrate may be returned to the grindinjjr mill for a short time but the circulatin<; load of 'tramp' iron soon builds up to a point where it becomes necessary to remove this concentrate and clean it up by hand.

The second system is as shown on tlie flow sheet of the 9-cu. ft. dredge above mentioned and involves the use of a Titan Amalgamator. Of the two systems the oin* with the Titan Anuilgamator seems to be the better and will probably eventually supersede the other sy.stem entirely.

On two dredges where the gold is very badly tarni.shed the arrange- ment has been modified as follows: The cleaner-jig concentrate goes

Sec. I]

Notes Ox Jigs For Gold Dredges Collins

l'LA( T.U MtNlNc; I'OH (iOhD IN CALIFORNIA

[P,ull. 13:

Fig. 29. Sanrt-drag, Summer X'alley DrtdgiriK Company, Sumpti

directly to a Titan Amalgamator which discliarjes to a mechanical dewateriiip: device which feeds a 2- hy 4-foot ball mill. The ball mill dis- charjies to a second Titan Amalframator wliich is followed by a 12-inch, two-cell scaven<,'er jijr. This lias worked extremely well, bnt the same resnlts conid probably have been obtained had the cleaner-ji<r concentrate been dewatered and jTround, then fed to one amal<ramator followed by a scavenfer ji<;.

The last dredre to be remodeled of wliicli we have aiiy record is the H-cn. ft. boat of the Sumpter Valley Dredfring Company at Snmpter, Ore-ron. This job as remodeled started np in July 1940. The tlow sheet is identical with the one shown excepting that a sand-drag is used to dewatcr the rougher jig concentrate. Figure 27 shows a 4-cell block of i-ougher jigs and figure 29 shows the sand-drag used on the Sumpter Valley job.

Treatment Of Black Sand

Black sand accumulates as a concentrate in the riffles or jigs used at placer mines to catch the gold. It occurs also as a natural concentrate on many of the ocean beaches of California. Under the sundry civil act approved Marcli 3, 1905, Congress directed the U. S. Geological .Survey to investigate the useful minerals contained in the black sands of the Pacific slope, and this investigation was subsequently enlarged to embrace the United States. Most of the samples collected were concentrates from the sluices of placer mines, but samples from the beaches near Crescent City, Upper and Lower Gold Bluff and Humboldt County were included ; also from the beaches from San Francisco south to San Luis Obispo, from the elevated beach at Aptos on Monterey Bay, and from the beach at Ocean Park near Los Angeles. A report on this investigation was pub- lished by Day and Richards The investigation included methods of separating gold and platinum, and the point is brought out that separa- tion is easily accomplished on sized sand with shaking tables of the Wil- fiey or similar makes. The sizing is done in a hydraulic classifier or with screens. Magnetic separation was investigated also.

Following is a summary of results from about 200 samples collected in California in pounds per ton. Each figure represents the largest amount in any sample.

Maximum found in lbs. per ton

Magnetite 1856

Chromite 1800

Ilmenite 1500

Garnet 1874

Hematite 1120

Olivine 836

Monazite 56

Limonite 552

Zircon 928

Quartz 2000

Unclassified (in one case largely pyrite) 2000

"Unclassified" includes grains containing more than one mineral.

Thus we see that a black sand may be entirely quartz or it may be nearly pure magnetite, chromite, or garnet, or it may be 75 percent ilmen- ite. Various combinations of the minerals mentioned above and others (rutile) are possible. Gold and platinum are often present. The sands from various localities have a wide range in composition.

Many persons have expressed an interest in separating the minerals mentioned in the above table and placing them on the market as indi- vidual minerals. As no commercial process has yet been dervised by means of which this can be accomplished at a profit, attention will be given here only to separating gold and platinum from the sand. The amount of gold and platinum in the sand is determined by standard methods of assaying and chemical analysis. Claims of secret processes either for assaying the sand or for recovering the gold and platinum should be regarded with suspicion.

The platinum is usually so small in amount that elaborate machinery for its recovery is not justified because of excessive co.st. The expendi-

1 Day, D. T., and Richards, R. H,, Useful minerals in the black sands of the Pacific slope, U. S. Geol. Survey, Mineral Resources U. S., 1905, pp. 1175-1258, 1906.

(77)

LACKK MINING FOR GOLD IN CALIFORNIA I Bull. 135

r

Vir,. :!(i. lii-acli-sancl being: worked witli (lii>-linx, iKjrttu-rii Humboldt ("oiiiity. Hvininted from Cdlifornxa Journal of Mines and Geoloffy, October 191,1, p. 50!,.

Sec. I] TRKATMKNT OF HLACK SAND 79

ture of $5000 for luacliiiuM-y that would ultimately recover only $1000 worth of platinum is uuAvise to say the least. Many persons who have attempted to recover platinum from the beaches in Del Norte and Hum- boldt Counties have failed to realize this. At times the action of the waves concentrates jrold and platinum in small areas of the beaches, and men are able to make good wages searching for these small patches of concentrate and working them by snuUI-scale methods such as long toms. Many attempts have been made to work them with machinery but all have failed because the deposits are too small to pay for the machinery.

A similar condition applies to black sand from placer mining. Only the large dredging companies have enougli of it to justify the expense of much equipment. A dragline dredge is not likely to recover enough black sand, but .sevei-al of them together will produce enough to justify a little e(iuipment for treatment. Several profitable businesses were operated in 1040 by men who collected black sand from a number of drag- line dredges and hauled the sand to small plants cfiuipped with amalga- mation barrel, small shaking table of the Wiltley or similar type, and a melting furnace. The eoncentrate often contains lead shot and bullets, which amalgamate. Enough gold sticks to the amalgam and lead to make refining in the furnace worth while. A little cyanide or lye is often used in the amalgamation barrel to clean tarnished or coated gold.

Recent practice of two large dredging companies in handling black sand is described below. Eai-lier methods are described in a report by C. McK. Laizure.'

One dredging c(mipany reduces the bulk of the sand removed from the riffles on the dredge-tables during clean-up to a volume of 90 cubic feet with a long tom on the dredge. This amount is sacked and trans- ported to a clean-up room ashore. It is ground in an amalgamation barrel in which several flat weights are placed to polish the gold, then discharged to a sluice and run over a pool of (piicksilver. A bafitie is l)Iaced above this pool of (juick.silver so that particles of gold will be forced downward against the quicksilver. The mixture of sand and water then flows over a copper plate treated Avitli (piicksilver to amalga- mate gold. KifHes in a sluice 1 foot wide below the plate recover plat- inum in about 100 pounds of sand. This is panned down by hand for final recovery of platinum.

Another dredging company accumulates larger (piaiitities of black sand and has a more elaborate plant ashore. Black sand is dumped into a bin from which a bucket-elevator rai.ses it to a small ]iulsator jig.' One of the functions of this jig is to remove tramp iron and other .scrap metal. About two buckets are filled per day from the hutch and this is worked down by hand for tarnished or coated gold and platinum. Overflow from the jig goes to a Straub rib-cone ball-mill then to a shaking copper })late treated with quicksilver for amalgamation, then to ii hydraulic cone. Some (luicksilver and a little amalgam are recovered in the underflow from this cone, but practically nothing else. This underflow is hand-

Laizure C McK., Elementary placer mining; in California and notes on the milling of gold' ores : California Jour. Mines and Geology, vol. 30, pp. 228-233, 1934.

:' Pan-American Kngineerlng Company, 820 I'arker Street, Berkeley, California,

Made by Straub Manufacturing Company, .")07 Chestnut Street, Oakland, Cali- fornia.

80 l'LA(i:U MININ(i I'OK GOI.D IN' CAT,1K0RNIA |r>u]1.13r)

worked. The overflow poes by pipe-line to a Wilfiey table by 8 feet. Concentrate from this table goes to a Wilfiey table of laboratory size, IJ by :i feet, roncentrate from the small table is hand-panned; mid- dliii'T is returned to the same table. Tailin*,' from the small table and middlin},' from the lar<re table to back to the ball-mill. Tailing from the large table goes to a hydranlic cone, from which the overflow goes to wa.ste. Underflow goes back through the entire plant.

If the three products that are hand-worked contain nnich rusty gold, they are treated in a second small ball-mill in batches for polishing. Amalgam is sometimes treated in a pebble-mill made of a 3-gallon stone- ware crock containing flint pebbles. This tends to free much of the platinum tliat may be entrained in the amalgam.

Drift Mining General Description*

Drift mining in the United States has been applied chiefly to the exploitation of buried Tertiary river channels in the foothills of the Sierra Nevada in California. It has also been applied extensively, although on a smaller scale, to the mining of rich streaks on or near bedrock in more recent gravels where pay dirt is covered with a thick mantle of unpro- ductive material. Ground may also be drifted where there is insufficient p:rade or water for hydraulicking or where conditions are unsatisfactory for dredging. Bedrock under rivers has also been drifted where it was impracticable to divert the stream ; however, loose gravel containing a large quantity of water cannot be mined successfully by drifting. Usually the method is one of last resort and can be applied only to rich gravel. Even under favorable conditions 6 feet of gravel on bedrock generally must average at least $2.50 per ton to be mined profitably by drifting. Ground that has been drifted by the oldtimers with limited capital has been worked by other methods later; in these instances the overburden carried enough gold to pay for mining on a large scale.

In the latter part of the nineteenth century many large and produc- tive drift mines were operated in California; according to Hill, 11 mil- lion dollars in gold was produced in California by this method from 1900 to 1928, inclusive. In the summer of 1932, however, there were no large- scale operations in the United States, and the production of gold by this method was relatively unimportant. Two well-equipped properties, Vallecito Western and Calaveras Central, were doing development work but no regular breasting. The washing plants were used when enough gravel had accumulated to run the plant most of a shift. A few men were emploAed at a number of old properties in an endeavor to find new deposits of gravel. At a few other old mines lessees were taking out a very limited tonnage from around old workings. Throughout the west- ern placer districts small operations were under way, but relatively little systematic breasting was being done.

Most of the present drift mines are operated through shafts, although ill the past some large and productive mines were worked by adits. In many districts large quantities of water must be pumped.

Ill mining, the gravel is either drilled and blasted or picked by hand to break it down, then it is shoveled into cars and trammed to the sur- face or to the hoisting shaft. At the surface the gravel is sluiced or put through a washing plant to recover the gold. The gravel from most drift mines requires mechanical methods of washing to disintegrate it and free the gold.

Milling practices bear no direct relation to mining methods at drift mines and are treated separately in this paper.

The following general description of drift mining consists of extracts from Placer mining in the western United States, Part III, Dredging and other forms of mechanical handling of gravel, and drift mining, U. S. Bur. Mines Inf. Circ. 6788, 81 pp., 1935, by E. D. Gardner and C. H. John.son.

Additional details on methods of drift and methods of washing the gravel for recovery of gold are contained in this bulletin in Section IV, In which individual mine.s are listed by county and described. See Calaveras Central, Calaveras County; Ruby mine, Sierra County ; and Vallecito-Western, Calaveras County.

1 Hill, J. M., Historical summary of gold, silver, copper, lead, and zinc produced in California, 1848-1926: U. S. Bur. Mines Econ. Paper 3, 22 pp., 1929.

2 "Breasting" is the term used in drift mining to designate the mining of the

gravel ; it corresponds to "sloping" as used in lode mining.

(81)

82 I'LACER MINING FOR OOLD IN CALIFORNIA [Bull. 135

Development General Development

TIk' j,'(MU'ral development plan of a drift mine usually resembles that (.f a lode mine vlleIe similar Hat-lying deposits are exploited. Lateral development and the blocking out of the pay gravel are modified to fit local conditions.

Bench deposits or old channels exposed by later erosion or covered by only moderate deptlis of overburden may be opened and mined throufrh adits. Ventilation shafts, however, may be required in exten- sive workin<,'s.

Deeply buried deposits must, of course, be mined through shafts. This form of entry also is used for mining relatively shallow deposits wliere adits are not practicable. Occasionally long drain tunnels will be run and the gravel mined a series of shafts sunk along the course of the pay gravel. I\Ioreover, shafts may prove more economical for mining shallow deposits where their use obviates long underground trams. Conversely, adits may be run for drainage and to work gravels which have been developed through shafts.

Some of the ancient channels are buried as mucli as 500 feet deep by later gravel and lava Hows or beds of volcanic ash. The gravel is hoisted through a central shaft ; one or more auxiliary shafts usually are required for ventilation. A buried gravel deposit generally is prospected by a drift along the course of the channel and crosscuts from the drift to either lim. Kaises also are occasionally put up to prospect for possible rich strata above. As stated elsewhere, the buried Tertiary channels of the Sierra Nevada are not related to tlie present stream system; competent geological advice is needed to plot their probable course and aid in their development.

Adits sliould be run at such a horizon or .shafts sunk deep enough to insure di'ainage in the Avorkings. Drifts generally are run upstream to allow drainage to the shaft or out of the entrance adit. Where water is not a serious item drifts may be run both ways from a crosscut or a shaft; any water from the downstream branch is pumi)ed into the drainage sys- tem. The brea.sting is done upgrade by retreating toward the shaft or cro.sscut. At drift mines in the frozen gravels of Alaska the common practice is to drift in both directions from a shaft.

Ideal conditions, of course, would be an even bedrock and a grade sufficient to allow drainage but not too steep for easy tramming; such conditions, however, .seldom exist. A prospecting drift may be run partly in bedrock to avoid swinging it from trough to rim and back again .so as to keep a practical grade for tramming. With a rapid rise of bed- rock, h<wever, as where a waterfall or rai)ids existed in the original stream, the drift has to be run entii-ely in bedrock with raises put up to prospect the gravel above or the drift continued on a higher level with a transfer point at the break. This, of course, increases the cost of han- dling the material. If the size of the deposit as shown by the develop- ment work justifies the initial expense, tramming drifts may be run on an even grade in bedrock and the gravel from breasting operations above dropi)ed into raises from which it can be drawn into cars. Then the development drifts and crosscuts are used for extracting the gravel.

Sometimes drifts at different levels are run from the shafts to mine deposits at these horizons. More than one channel may be worked from the .same .shaft.

See. I] DRIFT MINING 83

In sliallow deposits little or no meclianical equipment may be used except for hoistinj;; in small-seale work lioistinf? also may he done by liand. The development and mininjr of deeply buried channels require expensive installations and usually must be done on a moderately large scale. Iloistins' and pumpiufr equipment and air compressors such as those used for lode mininjr are re(iuired for mining: this type of deposit, as well as air drills and mechanical haulage equipment.

Shafts. Siiafts seldom have over three compartments; in small- scale Avork one compartment usually suffices. Untimbered shallow shafts may be as small as 2 by 5 feet, the minimum section in which a man can dig.

Sinking practices are similar to those at lode mines except that blast- ing is seldom done; the gravel is loosened by picking or moiling. The shaft lining asually consists of lagging back of standard framed-timber sets.*

Considerable water may have to be handled in sinking deep shafts in gravel, in which case ample pumping capacity is needed. Ordinary sinking pumps usually are employed. Steffa has described the sinking of a 2-compartment shaft at Vallecito. California, in which a novel method of handling the water was used ; other sinking practices at this mine, how- ever, conformed to the general practice. He states :

'The shaft of the Vallecito Western was located at a point 50 feet north of the actual channel in order that the shaft station, at a depth of 153 feet below the collar, niifcht he in the solid .slate bedrock. At the point selected the shaft passed through 14.3 feet of volcanic cobl)le, ash, and sand and gravel before reaching the slate. It was sunk a total depth of KiT feet, providing a 14-foot sump below the station.

"The shaft is 4 feet by 7i feet in the clear and has one 4- by 4i-foot skip com- partment and a 2- by 4-foot manway. It is timbered with 8- by 8-inch Douglas fir, excepting that 6- by 8-inch material was used for dividers, and is lined with 1- by 12-inch boards.

"The shaft was sunk to Itedrock without blasting, picks and gads being sufficient to loosen the material for .shoveling. The 24 feet through rock was sunk by hand drilling, using 10 to 12 holes per round, light charges of powder, and electric delay detonators.

"A 12-inch churn-drill hole was sunk first at one end of the shaft to handle the flow of water which was struck at a depth of 8 feet and amounted to about 3.j gallons per minute throughout the work. The hole was sunk to a depth of 187 feet and cased with perforated 7-inch in.sjde diameter stove-pipe casing. A deep-well type of turbine pump was installed which was powered with a 20-hp. vertical electric motor, the motor resting on staging about 4 feet above the shaft collar. Three-foot lengths of pump column were used, and as the shaft deepened from day to day enough blocking waa removed from under the motor support to keep the pump intake at the level of the i)ottom of the shaft. When blasting, during the latter part of the work, the casing and punip column. exi)osed in one end of the shaft, were protected from damage bv a heavy plank hung from the bottom end plate directly in front of the drill hole.

"Xumerous strata of sand and volcanic ash were encountered, one such bed at a depth of 70 feet being 7 feet thick. A large part of this fine material was carried to the surface by the pump. A test showed that at one time the pump discharge was one-third sand by volume. The pump Impellers wore rapidly, three sets being used. Moreover, the drill hole rapidly filled with .sand to the level of pump, after which the pump could not be lowered farther. Twice the pumj) was removed and the h(de cleaned with a sand pump. Finally, at a depth of 75 feet, this difficulty was remedied by cutting a slot in the casing of the hole, wide enough to in.sert a hand to clean out the sand. As tiie shaft deepened the .slot was likewise cut down. To .secure suction with a shallow sump, such as could i)e dug out easily by hand in this manner, a 4-inch strainer was substituted for the original 3-foot one. The pump was run continuously

3 Gardner, E. D.. and John.son, J. F., Shaft-sinking practices and costs- tt Bur. Mines Bull. 357, pp. 4S-G0, 1932. cosis . u. fa.

Steffa, Don, Gold mining and milling methods and costs at the Vallecito Westprn drift mine, Angels Camp, Calif. : U. S. Bur. Mines Inf. Giro. 6612, p. 7, 1932.

.S4

PLAfKR MININC I'OR (UHA) IN CALIFORNIA [.l.Sr)

Vertical Section

6-inch I beam

ganger

—

r""

iJ

' 1

b

In

b

o

U- (he

HANGER vy sttel)

"

1 " H

6-inch I beam

jcHanger

H

r

Lj

I I I J

Plan

Fio. 31. Method of spiling in loose ground.

♦2-

Sec. I] DRIFT MINING 85

and regulated by the gate valve on the discharge pipe to the exact amount of water flowing into the small sump.

"It required 00 days to complete the siiaft. The average progress in sinking, including timbering, was slightly less than 1 foot per shift, working two 8-hour shifts per day. The cost was $39.50 per foot. Shaftmen and the foreman received $6 per day and engineers $5. Timber and lumber laid down at the shaft cost $42 per thousand board-feet."

Drifts and Crosscuts. As used in this paper, a "drift" designates a development working- parallel to the major axis of the deposit ; a " cross- cut" is a transverse working. This distinction is not observed strictly in the terminology of the mining districts.

Drifts may be run as small as by 5i feet in section where the han- dling of a minimum of material is desirable. In pay dirt they may be run up to 7 by 9 feet in size or as large as they can safely be held. The size of crosscuts depends upon the service required of them.

The gravel in the ancient channels generally is compact enough to stand Avithout timbering; blasting usually is required. The number of holes required to the round depends upon the compactness of the gravel. A simple toe-cut round — that is, one with the cut holes pointing down- ward— usually suffices for breaking the ground. It is desirable when blasting pay dirt in both development work and breasting to pulverize it as much as possible to facilitate washing operations. Ileavy blasting, however, should be avoided so as not to scatter the gold-bearing gravel. In loose gravels the main difficulty in driving may be to prevent caves until the timbering is in place; the gravel is excavated by picks and shovels.

Wheelbarrows may be used in short drifts or buckets on trucks in small-scale work where the broken material is hoisted. In more elaborate workings, however, cars running on rails are employed.

For drifting in pay dirt, a wide drift may be run and the boulders piled at the side to form dry walls. Where timber is brought from a dis- tance regular drift sets of square timber generally are used for support- ing the drifts, but if round timber is available locally sets usually are made of it. The posts of the sets generally are stood with a batter so that the drift may be given a section more nearly approaching an arch.

In loose or running ground spiling or forepoling must be used. The first step in spiling is to place bridging over the foremost standing set. Bridging u.sually consists of a 4- by 8- or 4- by 10-inch lagging laid par- allel to the cap on top of 6-inch blocks at either end. This lagging is blocked solidly to the ground above, leaving a space 6 inches high above the cap through which the spiling is driven. If side spiling is necessary bridging is placed on the outside of the posts. Spiling usually consists of 2- to 5-inch timber 4 to 10 inches Avide and as much as feet long, depending upon the weight to be borne and ease of driving ; one end of the spiling is sawed on a sharp bevel. The top spiling is driven at an upward angle into the caved or loose ground. In mines having com- pressed air a drilling machine with a special tool may be used for driving the spiling. The spiling extends over the cap far enough to provide room for placing a complete set. The upward angle is sufficient to allow bridg- ing to be placed over the new set. The first spiling usually is driven at one side of the bridging close to the bridging block at such an angle that the forward end when in place will be 6 or 8 inches beyond and above the cap and close to the wall. The remaining ones are driven at such angles

86 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

that they "fan" and form a complete covering for the set of timber to be pnt in place. As each spiling is driven ahead some of the gravel i3 cleared away from nnderneath it so that if any large boulders are encoun- tered ahead of the spiling they can be barred out of the way or taken down. After the top spiling is in place side spiling, if necessary, is driven in the same manner, beginning at the top. Two 6-inch I-beams, or heavy timbers, are then hooked on tlie la.st cap by heavy steel hangers. The ends of these beams are extended forward to just back of where the cap of the ne.xt set will be when in position. A crosspiece is then placed across their forward ends and brought up snugly against the spiling; the back ends of the beams are blocked down under the second cap back. "When the gravel is removed the next set is put in. The beams support the top spiling while the set is placed. Posts and caps of ordinary drift sets are used.

The same method of top spiling is used for breasting in running ground. The I-beams or timbers with overhead lagging may be used in firmer ground to protect men working ahead of the last set in position from falling material, both in drifting and breasting operations.

.Steffa gives the drifting practice at the Vallecito drift mine as follows :

"Both f,'iin>,'Wii.v.s and crosscuts are generally 7 by 7 feet in sectiou. The usual (hill riiimd consists of six holes drilled or feet deep and lireakiiiK an average of 4 feet per round. The gravel drills easily, 2i hours generally being sufficient to drill the roun<l. Drill steel is of |-inch hollow-hexagonal material, sharpened with cross bits. Slightly nii>r' than jiounds of '2'> percent strength i>owdfr is used per round, with four sticks in each of three lifters, three sticks each in the two cut holes, and two in the single back hole. Caps are treated with a standard waterproofing compound.

"The broken gravel is shoveled by hand into IS-cu. ft. end-dump, roller-bearing cars holding 1 ton each. Track consists of IG-pound rails laid to IS-inch gage. The grade of the channel has proved uniform over considerable distances and averages 75 feet to the mile. Track has been laid therefore on a grade of 11 percent upstream. It has seldom been necessary to take up bedrock to maintain the grade ; wherever a dip in the floor has Iteen f<iund the track has been kept on grade, and bedrock has always been found at the expected elevation when reaching the oi)posite side of the dip.

"In the opening of new areas by drifts or crosscuts, .samples are taken from the skip at the collar of the shaft, a .sample consisting of one full pan or about 20 pounds of gravel. Samples taken at this point have the advantage, as compared with samples taken from the .solid face, of being representative of a larger volume of ground and of being mixed thoroughly by the blasting and by the handling of the gravel from muck pile to car and to skip. Thus an experienced paiiner is able to make fairly accurate estimates of the value of the gravel developed.

"Drifts and crosscuts are driven by crews of three or sometimes four men, making an average a<lvaiice .f 4 feet per shift. The cost of driving main headings averages to $17 per foot. In a pay area (5.j feet wide, where gravel can be breasted 10 feet high, eiich foot of heading developinl 4." tons of gravel. (It is estimated that the gravel ex|>ands one (piarfer on being broken, and a ton of broken gravel has a volume of cubic feet.)"

The cost of running a drift under average conditions at a small-scale ninie where no other work was being done was shown by the Golden Belt (iold Mining Company which was developing a drift mine on Magpie (iidch near Helena. Montana, in the summer of lU'.Vl. An 80-foot shaft had been sunk, and a drift was being run up the channel ; the drift was 160 feet long and 5 by 6 feet in section and was timbered with 8-inch round timber .sets placed 4 feet apart. The top and sides of the drift were hned with split lagging. The timber was cut and sawed on the t?''"""d. The gravel was picked by liand and trammed in a 6-cu. ft. car.

drift mine. Angels Camp. Calif.: U. S. Bur. Mines Inf. Circ. 6612, pp. 8-9. 1932.

See. I] DRIFT MINING 87

It was hoisted in the body of the car, which at the surface was placed on a truck and trammed to the washing plant. The cost of running the drift was $6 per foot, excluding supervision. The surface equipment at the shaft consisted of a headframe and a hoist run by a 15-hp. electric motor. Power cost 1.07 cents per kilowatt-hour.

An example of the cost of running a drift under adverse conditions in small-scale operations was illustrated at the Lucky Charles Mining & Milling Company small drift mine on North Clear Creek, Blackhawk, Colorado, which in July 1932 was being developed through a 40-foot 2-compartment shaft ; 50 feet of drift had been run but no breasting done. The property was well equipped with an electric hoist, a deep-well pump, a substantial headframe, and an ore bin. About 20 gallons of water was being pumped per minute. A 10-hp. motor operated both the pump and a hoist which had an 18-inch drum. The gravel was hoisted in a 7-cu. ft. bucket attached to a -inch cable.

The gravel was 3 to 5 feet thick and was overlain with 5 feet of quick- sand which required both top and side spiling. The drift was 6 feet high, 5 feet wide at the top, and 6 feet wide at the bottom. Sets of 6-inch round timber were placed 2 feet apart. Top spiling was 3 by 6 inches by feet ; side spiling was 1-inch boards.

An advance of 1 foot per day was being made by 2 men underground and 1 man on the surface. The cost per foot of drifting was as follows :

Labor (3 men at $4) $12.00

Power (hoisting) 1.00

Timber 1.80

Other supplies 1.00

Total $15.80

Breasting

A number of different methods of breasting are employed at drift mines, depending mainly upon the nature of the deposit. Drift-mining methods were evolved in the early Californian diggings ; present methods do not differ materially from those of the early days.

In narrow channels the gravel may be mined on either side of the drift as it is advanced or the drift advanced the full width of the pay streak. In wader deposits the drift may first be run to the limit of the deposit and then the gravel mined, retreating toward the shaft. In exten- sive deposits the gravel usually is divided into blocks preparatory to min- ing. The blocks generally are mined by retreating. Pillars usually are employed only to protect haulageways. A modified room-and-pillar sys- tem, however, has been used at some mines in which the pillars, if in rich gravel, were later renoved.

Breasting may be done from crosscuts or from drifts run parallel to the haulageway. Breasting from the crosscuts may parallel the haul- age drift on the retreat toward it. When working from drifts the line of retreat usually is parallel to the drift although sometimes toward it. The spacing of crosscuts or drifts at different places ranges from 40 to 200 feet, depending mainly on the sy.stem of breasting. Crosscuts generally are turned off at such an angle as to give the proi)er gradient for tram- ming.

Cuts or slices range from to 8 feet wide. If cars are used in long faces the tracks are shifted after each cut. Usually all of the gravel rich enough to mine and enough of the overlying gravel to provide head-

88 Placer Mining For Gold In California [. 1M5

room is taken out. Rooms generally are 6 or 7 feet high ; the minimum height in large operations is 5 feet. At the Valleeito mine, described later, the thickness of the pay dirt varied up to 14 feet, although at most mines it was less than 6 feet. The rooms may be broken to a strong strata of ground where such strata occur. In some California drift mines vol- canic ash makes a strong roof.

In compact or cemented ground the breasts are broken by blasting drill round ; holes may be to 6 feet apart. At most places, however, breasting is done with picks. At many places the gravel is undercut, usually in the upper and softer part of the bedrock ; tiie remaining gravel in the face is then broken to the undercut. Usually 1 or 2 feet of bedrock is taken up. Often, bedrock with deep crevices containing gold can be picked. Hard bedrock is cleaned carefully by hand, as in surface min- ing. Boulders and gravel too low in grade to take out are piled back of the working face.

Low-built cars usually are preferred for the sake of easier shoveling and tramming in the low workings. Scrapers in drift mines have not proved successful, but with the recent improvements in equipment and technique this method of moving gravel offers possibilities.

Some timbering usually is required in breasting, if only an occasional stuU which may be recovered later. Regular timbering consisting of stulls with headboards is used at most mines. If the bedrock is soft, foot- boards also are used ; in soft ground lagging is required overhead. Heavy ground generally is supported by lines of sets. In narrow channels tunnel sets with long caps may be used.

A Synoptic Presumption Regarding California'S Drift Mines

By L. L. Huelsdonk*

In years past, including but not considering the war and closing order L-208 of the War Production Board, there have been many theories advanced, from the rapid extinction of the old-time gravel miner and the inability of the present generation to absorb his art to the exhaustion of the ancient river channels, for the sick condition of the California-sired and once booming drift mines. The actual reason is without doubt economic, and depletion of the easily accessible channels is probably the chief contributing factor. However nearly all of the successful drift mines operated at a time prior to the epoch of laws, rules, regulations, restrictions and taxes governing compensation, unemployment, social security, sales, income, corporation, labor, forest, water, transportation, tailings, and many other seemingly unimportant riders regulated under some admixture of the ABC's which directly or indirectly affect present- day operations.

In the so-called 'good old days' a drift miner often wore knee-pads, worked long hours under a goose-cooker, back-filled boulders and waste and loaded only select pay dirt into his breast buggy. This was trans- ferred to cars and trammed to the outside washing bins by Chinese labor where even in the larger mines, the superintendent had the time and did in most cases wash the gravel and make the clean-up, He fed the white miners beans and the Chinese rice, and if after meeting the payroll and bills an ounce of gold remained the mine was a profitable one. He needed no accountant, income tax expert, attorney or engineer to esti- mate ore reserves, values, percentages of depletion or other incompre- hensible guesses to determine if the profit was actual or merely one on paper.

The foregoing is not an advocation for the return of the good old days' Qr is it without exaggeration or exceptions. Its main intent is to express in brief generalities, for comparable purposes and the sake of argument, conditions that existed during California's early-day drift mining history. As a conservative estimate these mines had an over-all cost of possibly $3.50 to $4.00 per man-day as compared to an immediate pre-war average of $10.00 and a probable $15.00 post-war outlook. This means simply that on the basis of a 50-man crew the early day operation had a monthly cost of approximately $5600.00 as against $15,000 in the late 1930 's and $22,500 for crystal ball operations. So in order to keep the unit cost of gravel washed on an equal basis it will without much doubt be necessary for the post-war operator to wash four times the num- ber of units per man as did the old timer and one and one-half times as many as those washed just prior to the war. In comparing these (exclud- ing tax and other ABC nuisances which have been included in the man- day costs) many other factors must be considered, such as the highly publicized $35.00 gold and the possibility of a future increase, the amount of waste mined with pay, the efficiency of up-to-date equipment and

Superintendent, Ruby mine, Downieville, California. Mr. Huelsdonk explains in a letter that these remarks apply to drift mining in general and that exceptions exist, such as the Ruby, where rich beds of coarse gold are found ; but that these have little bearing on the industry as a whole.

(89)

DO PLACKR MININC VOH COlAy IX CALIFORNIA [. 135

lUJU-hituM-y, workiii;,' liours, iiiodeni explosives, high-?rade control, gold recovery, niaiiapeineiit and eiiprineeriiig facilities. Since most of these are incidental we will consider only the first {rronp, that is $35.00 pold, its possible increase, the efficiency of modern equipment and the ratio of waste to pay mined. The old timer mined very little waste, he worked by hand, tlie {gravel was prospected, he .skipped the ]K)or, mined the pood, and at times took only a few inches of bedrock <xravel by back-filling waste and Icaviiif; enonph room to work. Even if the post-war man wonld snbniit to this type of mining the over-all cost per miner would without doubt be j)roiiibitivc and therefore any post-war drift mine plans nnist include the use of modei-n eciuipment if success is to be reas- niiably expected. However, this is not an over-all answer or is it without drawbacks. What we might consider modern drift mining equipment are<nncking machines and slusher scrapers supported by various acces- sories such as power augers, jack legs, air bars, drifters, electric loco- motives, etc. To begin with, even the smallest mucking machine requires a seven-foot high face to woi-k in and if in a timbered drift, eight feet. It reipiires a track, and grade must be maintained. Tts operation cannot be held up while boulders are sorted out and back-filled, as its prime pur- pose is a muck moxci- and any delays must be ))roi)()rtionately charged to costs. Also since the bulk of the gold lies on the bedrock or a few inches above it in mo.st drift mines, breasting with a mucking machine usually causes undue dilution. Tts use, however, is indispensable around the modern drift mine for running bedrock tuiniels and where applicable for opening up grouiul for slushing.

liy breasting with .slushers a fairly nu)dcrate roof heiglit can be maintained. This must, however, be at least five feet in order to make working roojn and conform substantially to modern working conditions. P>y usi)ig blasting boards to keeji from scattering the ])ay over the worked- out areas and at the .same time utilizing them for a scrajier way during the nuicking cycle a good condition is civated for back-filling boulders in the open breast. Heavy rocks can be pulled over the boards by use o£ the tu<rger and a duiin net sling. A scraper also has the advantage of following over irregular bedrock (when the gravel is reasonably dry) without grade or drainage. It is also a good bedrock cleaner when l)roperly applied. In other words, the slusher, under ideal conditions is a hard combination to beat for brea.sting purposes. It is not however, without faults and disadvantages. The scrapers have a tendancy to cut and follow troughs in the broken gravel making it hard to crowd the face and mechanically clean uj) the breast for drilling. In wet ground they stir and mud the gravel making a .sticky nui.ss which is very difficult to handle in the chutes, cars aiul ore bins. Tender these conditions they sometimes bury themselves and <'Ut deep into the softer bedrock spots forming i)\Kldle holes wliich catch more water and tend to further wet the nnick. Also selective breasting cainu)t be carried on .successfully as the main theme nuist be the .si)ii-it of high production and low costs and therefore the drilling and mucking cycles cannot be interrupted. In (( woi-ds with a hundred-foot breast face with fifty feet averaging $fi.00 and fifty feet averaging 10 cents the entire leiigth'must necessarily be taken rather than rearrange set-ups to take .select sections. This further tends to dilute; the pay when comparing it to the old-timer's work. Also tugger stations contribute waste and their setups absorb man power.

Sec. I] CAI.IFOUNIA's DKIFT MINKS — TU'EI-SDONK 01

In suuiniiiig these groups we might say tliat iiiodeni breasting, no matter how closely guarded, will add an equal amount of waste to the pay gravel mined by the old-timer, so therefore, although the present price of gold is $35.00 per ounce it lias a modern drift mine value of only $17.50 as compared with .$20.67 for the old-timer. Consider with this the four to one mining ratio anticipated for post-war operations and the gold for this operator will have a value of less than $5.00 per ounce on a com- parable basis. In other Avords, to balance the two periods, the post- war drift mine operator should get $41.34 per ounce for his gold to com- pensate for dilution necessary with modern methods, and since he will be required to wash four times the amount of diluted pay dirt to obtain an equal unit cost he should receive a total of $165.36 per ounce for his gold to reach the boom basis of the drift miner's heyday.

These figures, although subject to considerable variation, will serve in a general way to explain the sick condition of California's drift mines. Providing that gold remains at its present value or enjoys an increase with a compensating sur-tax the post-war drift mine operator, in order to effect a cure, must be a strong-minded, hard-headed doctor willing to suffer public criticism by experimenting with and practicing ultra- modern methods such as tlie rapid back-filling and tamping of waste into the 'worked-out' areas by specially designed machines that will insure safe working conditions aud eliminate to a great degree one of the indus- try's main bugaboos, the expense of timbering. He will have to work out a ratio between the expansion of his broken ground and the tightness of his back-fill whereby he will be able to haul out and wash only his richer bedrock gravel and thus minimize transportation and milling costs. His development program miLst be carefully laid out and his plans must include the mining of the entire bedrock area as there can be no applied rule for following the pay .streak in this type of mining and as some gold usually spreads over the bedrock aside from the run of gold the effort would in most cases be compensated for hy low mining costs.

The small amount of gold accompanying the upper gravels which would go into the back-fill would no doubt be cheap pay for the fill material.

In conclusion, it might be generally .said that if gold remains on a par with its present value and if the po.st-war drift miner is to enjoy the higher (or any) income tax brackets, he must develop and adopt a more streamlined mining system rather than knock his brains out against Davy Jones' locker with the present day conventional methods.

PLACKR MINIXt; I'OK GOLD IN CALIFORNIA [Bull. 135

Fig. 32. Flume for hyflraulic mine under con.><trutti(in. Pliolo by C. V. Avcrill.

HYDRAULIC MINING* i. . Application

; Jn hydrfulic niininp: a jet of water issuiiif]: under high pressure from a nozzle excavates and uaslies the gravel. The gold is recovered partly by,cleaiiing bedrock after the gravel has been .stripped away but chiefly by riffles in the sluice box through which the washed gravels and water flow to the tailing dump.

Almost all types of placer deposits can be worked by hydraulicking if water is available but certain physical characteristics have an impor- tant bearing on the cost of the operation. If the gravel is clayey, the washing is more diffieuJt but more important. If the gravel is cemented, it can be cut only by high-pressure water. If the grade of bedrock is flat, the duty (cubic yards per miner's inch or other unit) of the water is relatively low, and where gravity disposal of water and tailings is impossible or impracticable elevators must be used to raise them from the pit, further decreasing the capacity of the installation.

Apart from the deposit itself, the water supply is the most important factor in determining the application of hydraulicking and the scale of operation. Under any given conditions, the daily yardage is roughly proportional to the quantity of water used. The quantity excavated likewise is proportional to the head used on the giants, but the higher pressure is of less value in driving and washing and of none at all in sluicing the gravel through the boxes to the dump. As the cutting and sweeping capacity of the giants usually exceeds the carrying capacity of water a stream of flowing water, known as "by -wash", or "bank water", is directed through the pit and into the sluices. If run over the bank, as in ground sluicing, it aids materially in cutting the gravel. The proper relative quantities -of high pressure and bank water can be determined only by trial. Frequently the by-wa.sh is supplied by the natural flow of the .stream at the mine, the giant water being brought from a considerable distance up the stream or from another source. "When an excess of bank water is available it may be used for ground-sluicing, thus increasing the capacity of the plant.

The preparatory or development work necessary to start hydraul- icking usually is greater than that for any other form of placer mining except dredging or drift mining. A deposit preferably is opened at the lower end to permit gravity drainage and progressive mining of the entire deposit in an orderly fashion. If the gravel is thick or the grade of bed- rock flat, a very long cut may be neces.sary to reach bedrock at the desired point. This may involve the mining of large quantities of barren or at least unprofitable gravel. A more important element of preparatory cost is the water supply. As heads of 50 to 300 or 400 feet are desired, a mile or more of ditch or flume is almost always necessary to bring water onto the property by gravity flow. A single mine may have many miles of

The following infoiiiiation on the general subject of hydraulicking consists largely of extracts from Placer minUty in the western United States, Part II, Hydraul- ickimj, treatment of iihucr concentrates, and viurketiny of ffoUl, U. S. Bur. Mines Inf. Circ. 6787, pp. 3-1 US, 1934, by K. D. Gardner and C. H. Johnson. Many of the tables contained in that publication have been omitted. Tables showing flow of water in pipe-line-s and ditches and over weirs will be found in books on hydraulics such as Hydraulic tables, by G. S. Williams and Allen Hazen, 115 pp., John Wiley & Sons, Inc., New York. Gardner and Johnson published tables of prices of pipe and other equip- ment, but these have sUiee changed and are likely to change further from time to time. Hence such prices should be obtained from manufacturers.

(93 )

94 PLAf:r.R MININT. FOR nOLH IN CAMFORNIA [. 1!")

ditch, costing perhaps $2, ")()() per niilo, as well as dams and resorvoirs and thousands of foet of flinnos, tunnols, or inverted siphons. The mechan- ieal e(piipinent of a liydraulic mine oi-dinarily consists of a few hnndred to a few thousand feet of lO-to :{()-inch, or lar{,'er, iron pipe, one or more monitors, and a varyin<: number of sluice boxes; the cost of equii)ment ordinarily is small compared to the expenditures necessary for ditches and tail races.

Althonjrh it is obvious that the recoverable gold content of the gravel nnist pay a profit over operating costs, which usually range from 5 to 20 cents per yard, a surprising number of ventures in hydraulicking have failed becau.se the promoters have not allowed for all the preparatory expen.ses noted above. Each yard of gravel mined must carry its share of this cost, therefore the size of the deposit is of utmost importance in considering a hydraidic mining venture.

Hydraulicking under .suitable conditions is a low-cost method as it yields a larger production per man-shift than any other method except dredging. The initial investment recjuired is less than that for tlredg- ing; hence, hydraulicking in small or medium-size deposits may be more economical even though dredging would result in a lower operating cost. When tiie operations are on a very large scale hydraulicking costs are lower than dredging costs on a comparable basis. Very clayey or bouldery gravels .should be hydraulicked as dredging usually is unsatis- factory in such ground.

There is enough similarity in all hydraulic operations that no natural classifications of the method can be made. The methods of attacking the gravel vary too little to make any general distinctions. Factors sucli as conditions of the gravel, percentages of boulders and clay, grade of bedrock, and quantity and head of the hydraulic water affect the co.sts, but no general grouping is possible in accordance with any of these heads.

Ditches

Open ditches are used c(mnnonly to bring water close to, yet high enough above, the mine to furnish a satisfactory pressure for the giants. At several hydraulic mines in the Western States and Alaska ditches 30 to 40 miles long have been built, and even relatively small operations usually have 5 to 10 miles of ditch line.

Hydraulicking is feasible with heads as low as 40 or 50 feet if the gravel is not tight ; however, heads of 80 to 200 feet usually are desired, and if the gravel is cemented it is not uncommon to employ high-pressure equipment and heads raiiging from 'MK) to 400 feet. This consideration fixes tentatively the location of the lower end of the ditch. Its final loca- tion may be a matter of compromise, as the head usually can be increased only at the cost of a lengthened ditch or a decrease in the grade. The latter reduces the quantity of water that can be carried in a ditch of given size.

The grades of most hydraulic-mine ditches lie between 4 and 8 feet per mile, or J to feet per 1,000 feet. Early C'alifornian ditches were run on much steeper grades, but the conseciuent high velocities caused ero- sion of the banks and .serious breaks were common. Small ditches may- be run at grades of 6 to 12 feet per mile without excessive velocities.

Practical velocities range between limits of Avhich the minimum is determined by silting and the maximum by erosion. If the entering water contains sediment it may be deposited in the ditch. This should

Sec. I]

Hydraulic Mining

be {guarded ap:ainst by installing; a sand trap near the intake and by designing for a velocity of not less than 1 foot per second. On the other hand, a velocity of more than 3 feet per second is apt to erode the channel and cause breaks.

Table 1. Recommended mnaimum mean velocities for ditches in various materials

Mean velocity

Material

Loose sand

Sandy soil

Loam

Stiff day, gravel

Coarse gravel, cobbles

Conglomerate, cemented gravel, soft rock Hard rock

The figures in table 1 represent mean velocities, the corresponding bottom velocities being 20 or 30 percent lower and the corresponding sur- face velocities as measured by floating objects possibly being 25 to 35 percent higher.

The velocity, hence the capacity of a ditch, depends upon its slope, the nature of the walls, the size and shape of the water section, and the straightness and regularity of the channel. All these factors, except straightness and regularity of cross-section, are involved in the well- known Kutter formula :

41.65 +

1 +

R

m -f

in which

y mean velocity (in feet per second), n roughne.ss coefficient. S — sine of slope (fall divided by lenRtli) .

R hydraulic radius (area of water section divided by wetted perimeter of channel) in feet.

The proper values to use for the coefficient w are a matter of judg- ment. The values of n reeonmiended by modern designers are shown in table 2.

Earth canals for irrigation usually are designed with n — 0.025 or even 0.0225 ; however, the usual hydraulic-mine ditch is not straight, uni- form, nor smooth, and probably the coefficient 0.030 or 0.035 should be applied. Any increase in the assumed value of n results in an approxi- mately equal percentage decrease in the calculated velocity, or a doubled percentage increase in the required slope.

Although the shape of the ditch has a bearing on its capacity, in practice the section is influenced more by the method of excavation. However, for a giveti area, the section should be so shaped as to have the largest hydraulic radius consistent with economical construction. The usual earth or gravel ditch for hydraulic mines has a trapezoidal section,

place:r mining for oold in California [Bull. 185

Table 2. Values of roughness coefficient n

Surface

Best

Good

Fair

Bad

Coated cast-iron pipe

Commercial wrought-iron pipe:

Black -

Galvanized

Smooth brass and glass pipe

Smooth -bar and welded "OD" pipe

Riveted and spiral steel pipe .-

Vitrified sewer pipe

Common clay drainage tile

Concrete pii)e

Wood-stave pipe

Plank flumes:

Planed

Unplaned

With battens -

Concrete-lined channels.

Cement-rubble surface

Dry rubble surface

Semicircular metal flumes:

Smooth

Corrugated

Canals and ditches:

Earth, straight and uniform

Rock cuts, smooth and uniform

Rock cuts, jagged and irregular

Winding sluggish canals

Dredged earth channels

Canals with rough, stony beds; weeds

on earth banks

Earth bottom, rubble sides

'Oil ,013

'012 '013 '015 '014

'025 '0275

'030

'0.013

'013 '.017 '014 '015

'.016

'.0225 '.033

'.035 '.033

' Values most used.

Part of a more complete list by Horton, R. E., in Eng. News, vol. 75, p. 373, 1916 ; quoted by Metcalf. L., and Eddy, H. P., in Sewerage and sewage di.spo.sal, 2d ed., p. 130, McGraw-Hill Book Company, 1930.

with a flat bottom 2 to 10 feet wide, sides sloping about 45°, and a water depth Oi one-third to three-quarters the bottom width. The sides should be excavated at a slope that will be stable in use, otherwise caving will result in irregularity of section and consequent less of capacity. The side slopes recommended for ditches in various materials are given in table 3.

Wimmler, who tabulates data on 35 Alaskan ditches, states that side slopes of 45 to 65° are common but that the higher slopes cut down quickly.

On steep hillsides relatively steeper sides and deeper sections may be cut if the soil is firm to avoid excessive excavation on the uphill side of the ditch. In rock the sides may be vertical; the width should be twice the water depth, as in rectangular channels this results in the least excavation for a given capacity and slope. Likewise, in rock the size may be decreased and the grade increased, thus reducing the yardage of rock excavation. Ditches should be designed to run not more than three-fourths full, allowing 1 to 3 feet of freeboard.

' Wlmmler, N. L., Placer-mining methods and costs in Alaska: U. S. Bur. Mines Bull. 259, pp. 40-66, 1927.

HYDRAULIC MININa Tahle 3. Side slopes recommended for ditches

Side slopes

Material

Horizontal to vertical

Degrees

1 : 1 Ih : 1

2 :l

Ordinary soil, loose or fine gravel

Loose, sandy soil

III porous soil considerable water is lost by seepage. Peele quotes Eteheverry as stating that seepage losses range from as little as 0.25 cubic foot per square foot of wetted surface per 24 hours in impervious claj' loam to 1.0 cubic foot in sandy loam and 2 to 6 cubic feet in gravelly soils. It is easily computed that a medium-size ditch, 5 miles long, carrying 1,000 or 2,000 miner's inches, may lose 5 or 10 percent of the intake water by seepage, even in good soil, and in porous soil, as much as 20 percent. Remedies where the loss is serious are to decrease the size of ditch and increase the velocity; to reduce the velocity to a point at which the silt will deposit and tend to seal the ground ; to line the channel with sod, canvas, or concrete ; or to substitute flumes for ditches. According to Wimmler, sod lining often is used in frozen muck in Alaska, sometimes with entire success.

Very few ditches have been built in recent years, and no modern costs are available. Many methods are available for such work, ranging from hand-shovel and pick w'ork to excavation by power shovel or mechanical ditchers. A common method is to plow the surface and exca- vate as near to grade and correct section as possible with teams and scrap- ers, then finish by hand. Some instances have been noted where hydraulic giants were used for ditch excavation. This, of course, is pos- sible only when water is available from a higher ditch line. Incidentally the hj'draulic miner uses high-pressure water for excavating wherever practicable.

The alinement of ditches should be such that excavation to grade will provide just enough bank material to form a channel of the desired size. Wherever the water level is to be above the original ground surface it is well to plow the surface before excavation starts to form an impervi- ous joint between the bank and ground. If the material is not such as to form tight banks it may be advisable to excavate the entire water section below the original surface. The grade must be maintained exactly and the desired section adhered to as closely as possible, as all irregularities have a retarding effect on the flow. Curves should be made smooth and regular for the same reason.

If there is danger of water from floods or other sources filling the ditch beyond capacity, spillways must be provided at intervals to prevent breaks in the line which would stop operation and be costly to repair.

2 Peele, Robert, Mining engineers' handbook, 2d ed., p. 2147, John Wiley & Sons,

98 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. V.]')

Measuring Weirs. The simplest method of accurately measuring a flow of water in a stream or ditch is by means of a weir. Numerous types of weirs are used, and there are many formulas for calculating the flow over weirs.

The width of the weir notch should be at least six times the depth of the water flowing over the crest. The bottom of the notch should be level and the sides vertical. The weir notch is beveled on the downstream side .so as to leave a .sharp edge on the upstream side. The weir should be installed so that the water in the ])ond above is comparatively .still. It must also be high enough so that there is free access of air to the under- side of the ovei-flow slieet of water. A stake is driven in the pond 5 or 6 feet above the weir with the top of the stake level with the notch of the weir. The depth of flow over the weir is measured with a rule or square placed on top of the stake. The Francis formula is commonly used for

calculating the flow.

Q - 3.33 ud 3/2,

where

Q — quantity of water in cubic feet per second,

w width of notch in weir,

d — depth of water going over weir.

Flumes

As already stated, most hydraulic-mine ditch lines contain some flume sections. Flumes may be necessary where the line passes around cliffs or over ravines or desirable over porous or shattered ground where a ditch would lose mucli water or tend to cause slides. On steep hill- sides or where ditching would require much costly rock excavation a flume may prove economical ; finally, the cost of the line may be lessened and considerable saving made in the total fall by building a flume or trestles across valleys instead of ditching the greater distance around the head.

The same conditions should be considered in designing a flume as in designing a ditch, and the Kutter formula applies equally to both. The formula is used most conveniently in the form of tables or charts.

The low friction coefficient of board flumes may be used to advantage either by building a flume of smaller section or by decreasing the grade below that of the ditch line. If the latter is done a saving in head may be made at the mine. Usually, however, smaller sections and higher velocities are used than for the ditch line. The width of the flume should be twice the water depth and a freeboard of 1 to 2 feet allowed. Accord- ing to Egleston the usual water velocity is 3 to 6 miles per hour (4 to 9 feet per second) . The same author gives the range in grade of 28 promi- nent California flumes as 9 to'l8§ feet per mile. The extreme range of 86 well-known flumes in the Western States was 5 to 53 feet per mile, the usual range 10 to 18. and the average slightly under 14. Bowie* states that grades of 25 to 35 feet per mile are used where practicable. Such steep grades would permit the use of a relatively small flume section, but the authors believe that usually they would involve inconveniently high velocities; moreover, a longer flume would be required to give the same head.

Egleston, Thomas, The metaUurgy of silver, gold, and mercury In the United States, p. 152, John Wiley & Sons, 1890.

Bowie, A. J.. A practical treatise on hydraulic mining In California, p. 143, D. Van Nostrand Company, New York, 1889.

Sec. I] HYDRAULIC MINING 99

The construction of wooden flumes has changed little since the early- days of placer mining in California. The flume was built in 12- or 16- foot sections of 1- to 2-inch lumber, 12 to 24 inches wide. The longi- tudinal joints were made tiglit by nailing over each a batten inch thick and 3 or 4 inches wide. A flume 34 by 24 inches built about 1930 for water power carries about 600 miner's inches on the flat grade of one- fifth foot per 1,000 feet and would serve excellently for a small hydraulic water-supply line. It differs in construction from the other type chiefly in having splines between all the boards of the boxes and lacking framing in the sills and caps. It was built over 6,800 feet of rugged country at a total cost of $2.50 per foot.

AVhere the flume is on grade the box units should be set on stringers laid on a carefully cleared and graded surface or on a bench cut in the hillside. Trees or branches that might fall and wreck the flume should be removed. In cold climates the flume may be covered and heaped with earth to prevent freezing. AVhere the flume is on trestles a walk must be provided ; usually a line of plank is nailed over the caps or on alternate sills extended a couple of feet to one side of the box. The grade must be uniform, and at curves the outer edge of the flume should be raised suffi- ciently for the smoothest possible flow of water, the elevation being deter- mined by trial. Three-foot iron placer pipe cut in two lengthwise has been used successfully for flumes at placer mines in British Columbia.

Diversion Dams and Reservoirs

Diversion dams for hydraulic ditch lines usually are of earth-filled timber cribs or rock-filled cribs faced with boards. Small streams often are dammed by throwing logs across and facing the upstream side with boards. Diversion dams usually are only a few feet high but should be built where possible on solid rock or hardpan, sufficiently wide to be stable and provided with suitable spillways to prevent erosion and scour- ing out of the foundation.

At mines where the water supply is insufficient for 24-hour operation or where the stream flow is less than is needed to operate at the desired capacity for one shift, reservoirs often are used." If it is impracticable to have the resevoir in the stream itself above the diversion dam, it is usually located at the lower end of the ditch, just above the intake to the pipe lines. Keservoirs may be built by damming a canyon, by excavating a basin on level ground, or merely by enlarging a section of the lower end of the ditch. As a reservoir break might be disastrous to a mine lying directly below it, the work should be done carefully, all leakage checked, suitable gates and spillways provided, and regular inspection maintained.

As both diversion dams and reservoirs tend to act as settling basins it may be convenient to provide gates close to the bottom through which sediment may be flushed as often as necessary.

Mining Equipment

The chief items of equipment used in most hydraulic mines are pipe lines to carry the water under pressure to the places where it is used ; giants.or monitors for cutting, washing, and driving the gravel ; derricks, winches, or other machinery for handling boulders ; and sluice boxes for saving the gold and disposing of the tailings. Picks, shovels, and forks are the common hand tools used at placer mines. Power drills run by compressed air or steam may be used if the gravel contains an excessive

PLArKR MININO FOR GOLD IN CALIFORNIA

[Bull. 135

riu. .i:i. Pipe installation, 2- aii'i 54-incli. Photo hy l,ih, c, .s/, of Suttnaou Miniiiff Cotporutioii : rei)rintC(l Jrvin CuUjornia Journal of Mines and Geoluffy, January I'Jil, p. 56.

quantity of large boulders. However, hand drills are used at most mines to drill boulders and sometimes to drill cemented gravel or hard-clay strata. Churn drills are employed occasionally for drilling cemented gravel ahead of hydraulicking.

Pipe Lines

Pipe. As described pi-eviously, ditch lines are used to bring the necessary water to a convenient point above the mine. From that point a pii)e line is laid down the hillside to the pit. Occasionally, wiiere the grade of a creek is steep, the water will be diverted from the stream directly into a pipe line. Although wooden stave pipe is u.sed at a few projierties, steel pipe is preferred at nearly all hydraulic mines.

Pipe may be made from steel sheets in the mine shops or bought from l)il)c manufacturers. I'nless a large quantity of pipe is to be used or transi>ortation is difficult, it usually is more economical to buy the pipe already made jjp. Various types of steel pipe are used, but light-weight riveted pipe with slip or .stove-pipe joints generally is preferred in the Western States as it is cheaper, lighter, and more easily transported and installed than other steel pipe.

Sj)iral i-iveted ])ipe will stand greater pressures and harder usage than the straight riveted pipe, but it is more expensive. Moreover, flange joints, which are an added expen.se, generally are used with the spiral pipe. Ordinary riveted pipe of 10 to 16 United States standard gage material 7 to 46 inches in diameter was being used in western mines in lU.Ti; the diameters used most were 3G, 32, 24, 22, 18, 15, 11, and 9 inches. Large pipes are easily damaged if made of material thinner than 14 gage. Usually two or more diameters and gages of pipe are used

Sec. I]

Hydraulic Mining

Table J/. Maximum quanlity of slip-joint water pipe that can he loaded on flat car 8 feet 6 inches wide by .'/O feet long, using side stakes 10 feet high

Diameter, inches

Maximum number

Sections

Feet

1,152

8 137 50

6,006.25

5,115

4,262.50

3,487.50

2,790

2,480

2,170

1,898.75

16- . .

1,627.50

1,162.50

in the same line, mainly as a matter of convenience since this permits nesting in transit. A saving may be made in ocean freight and occa- sionally in truck hauls by nesting the pipe.

Slip-joint pipe is made in standard lengths of 19 feet inches each. The sections may be made longer or .shorter, however, as required bj"- transportation purposes, provided they are in multiples of 4 feet. The extra pipe required for a slip joint is about 3 inches per section. The standard length of sections of spiral riveted pipe is 20 feet. Placer pipe usually is coated inside and out with an asphalt paint.

A pipe of smaller diameter will withstand a greater pressure than a larger pipe of the same wall thickness; therefore, it is common practice to use smaller diameters as the pressure increases. Reducing the diam- eter increases the friction in the pipe, and a balance must be struck between loss of effective head in the pipe line and first cost of the line. Branch lines usuall}' have a smaller diameter than the main supply lines.

The minimum carload weight is 20,000 and the maximum 80.000 pounds in California. Carload shipments take fifth class rate. Less than carload shipments of pipe up to 12 inches in diameter take third class and over this diameter one and one-half times the first-class rate.

As used pipe is available in nearly all placer districts, very little new pipe is purchased except for installations of some magnitude. There are no established prices for used pipe.

102 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

The Y's and T's needed for branch lines usually are purchased from the pipe manufacturers. A header box may be used when more than two branches are taken out at one place.

Joints and Valrcs. In makinpr the pipe with slip joints the diameter of one end is slipfhtly contracted. This joint in straight pijie lines will withstand most pressures encountered at placer mines. Slip joints, how- ever, become battered from frequent layinj,', and other types are desirable wliere the pipe is moved often.

Flanged or bolted joints are used in some pits for siphons and in very high -pressure lines. The Taylor flanged joint is of forged steel and is welded to the pipe ; the price includes bolts and gaskets. The 8-inch size is good for a working pressure of 200 pounds; 8- to r2-inch size, 125 pounds ; 12- to 20-inch size. 110 pounds ; and above 20-inch size. 75 pounds. The American flange also is complete and attached to the pipe. Most sizes are good for a working pressure of 300 potnids per square inch.

Sometimes a lead joint is used ; this consists of a sleeve three-fourths of an inch larger than the pipe, placed around the two ends to be con- nected. The space between the ring and pipe is filled with molten lead.

Riveted elbows furnished by the pipe manufacturers generally are used for making turns in pipe lines. Taper joints are used where reduc- tions are made in lines. Sudden reductions in size are to be avoided because of the loss of head and strain on the line.

Standard valves are used for diverting water or closing off flow in pipe lines. Valves should be closed slowly and with great care in high- pressure lines; the pressure exerted by the sudden stoppage of flow in the water column may burst the pipe.

Air vents are needed at all crests in hydraulic pipes to prevent a vacuum being formed and subsequent crushing of the pipe. Venting also is necessary to prevent air pockets in the line. The device consists of a leather-faced flap on a hinge bolted on the inside of the pipe. A bail attached to the flap goes through an oblong hole by 3 inches in size, cut in the pipe. As the water fills the pipe the flaj) fits tightly against the inside ; as the water falls the flap drops, making a vent.

Pressure Boxes. To give the water entering a pipe line an initial velocity pres.sure boxes or penstocks are used. A head of 4 to fi feet u.sually is provided. A length of large-diameter pipe may be used at the top of the line instead of a penstock. A screen usually is placed at the head of the line to keep out trash. In some installations settling boxes are provided where solid matter may settle out before the water goes into the pipe, as such material may cause rapid wear of the nozzles of the giants.

Laying Pipe Lines. Pipe lines are laid by begiiniing at the bottom and working upward. Sharp curves are avoided wherever possible, and where used the pipe must be anchored securely to prevent the thrust of the water pressure from pulling the joints apart. Curves in a vertical plane are especially undesirable as they may cause air pockets in the pipe. The pipe .should be filled gradually for the same reason. In crossing small ravines a trestle should be built first and the pipe laid on plank for the complete distance.

In laying new pipe with slip joints the outside pipe is started over the end of the other, then heated with a blow torch, which expands the

Sec. I] HYDRAULIC MINING 103

outer pipe and melts tlie tar previously placed on the end of the lower pipe. As the heating is completed the upper pipe is driven home by hammoriufr on a block of wood placed at the upper end. The tar makes a water-tight connection. Where the pipe has been battered from previ- ous handling?. burla]> or sackinj may be wrapped around the joint before drivinjj. If leaks develoji they may be stopped by drivinj; in wooden plugs; .sometimes an outside band is recpiired.

In placing pipes with flanged joints they arc laid end to end and the bolts put through and tightened up. TheHanges usually are attached to the pipe at tlie factory. This prevents nesting of the pipe in shipping but permits a better joint to be made.

When pressures are very high or when the pipe has vertical or lateral curves, lugs should be riveted on the ends of the pipe with slip joints and the two pipes wired together after the connection is made to prevent the joint pulling out. Similar lugs can be used for anchoring the line to stumps or posts.

In straight pipe lines expansion joints .should be placed at intervals of ]()() to 2,000 feet, depending upon the conditions to be met. Where pipe lines have lateral curves expansion joints are not needed, as the expansion or contraction of the pipe is taken up in the curved sections. A long, empty pipe line may contract several feet between a warm day and a cold night, and unless provision is made for this contraction the pipe will pull apart. AVhen the iipes are kept full of water this con- traction does not occur. Pipe lijies are buried in .some locations but seldom at western placer mines.

The cost of laying pipe lines depends upon the size of the pipe and the topography and cover of the country. Ten men working 90 days laid 5,000 feet of 36- to 16-inch pipe at the Browning mine, Leland, Oregon, in open country in the spring of 1932.

Flow of Water Through Pipci. The quantity of water that will flow through a pipe line at a placer mine depends mainly upon the diameter of the pipe, the effective hydraulic head, and the size of the nozzle used on the giant at the end of the pipe. Generally the nozzle u.sed is of such a size that the pipe will carry the available water. As the water supply is reduced smaller nozzles are used on the giants.

The effective head on a pipe is the static head minus the loss of head caused by friction. The loss of head depends upon (1) the velocity of the water, (2) the roughness of the interior of the pipe, (3) the diameter of the pipe, and (4) the length. The pressure available and the amount of flow at the end of a long pipe depends mainly upon the last three items. The pressure of the water in the pipe has no effect, by itself, on the loss of head. Formulas have been derived for calculating the loss of head in Avhich coefficients of roughness are used. These coefificients have been derived by experiment for different types of pipes; specifically, however, consideration must be given to the service conditions oicountered. No standard of roughness exists, and the degree of roughness of the interior of a pipe does not remain constant. Usually a pipe is chosen about 20 percent larger than would be indicated if there was no loss due to friction. Flow through an unobstructed pipe line of uniform diameter can be calculated from a number of formulas. The Kutter modification of the

PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Fio. 30. Small giant In operation. Extra water (by-water) for sluicing In back- ground. Photo by C. V. Averill.

Sec. I I llYDRArMC MININO 105

Cliezy formula appears to be preferre<l by bydraiilic eii<>ineers. Tbe Cliezy formula may be stated as:

Tlie Kutter moditicatiou of tlu' Cbe/y formida is:

1.S11 0.0()2S1

where

T — nu'iiii vclcicity of flow, feet per scfoiul ;

C "cootticient of rotanljition," so-Ciillrrl ;

If moan hydraulic radius of the pijic, that is, the diameter in feet ;

,V hydraulic 'i ado or slope, in foot i)or foot of lon};th of a pipe of uniform size ;

n "co(>tticiont of ronjrlmoss," so-callod.

The value of n for riveted lap-joint pipe up to and including inch thick can be taken as 0.015.

Giants

A priant or monitor is a device -with a nozzle for directiuf and con- trolling; a stream of water under a hydraulic head. The fjiant can swing horizontally through a full circle and from 11° below to 55° above the horizontal. A box of stones is used to counterbalance the weight of the spout. A giant generally is set up in a pit by being bolted to a log or to timbers securely anchored in bedrock. Nozzles of different diameters can be used up to the diameter of the outlet of the giant to make allow- ance for variation in the quantity of water used. The giant and nozzle are constructed so that a rotary motion of the jet is prevented, and the water is discharged in a solid column. Giants are made for a wide range of service in 10 sizes, numbered 0 to 9, inclusive.

With heads of 100 feet or more deflectors are used for pointing the larger giants. A common type of deflector consists of a short section of pipe that projects over the nozzle. It turns on a gimbal joint and is controlled by a lever. As the deflector is turned against the jet the force of the stream turns the giant in the opposite direction.

Table 5 shows the sizes, weights, and prices of giants and deflectors made by one manufacturer. Other companies make similar equipment at competitive prices.

Discharge Through Nozzles. Table 6 gives the discharge through different sizes of nozzles under heads from 100 to 400 feet. In this table 40 miner's inches is considered as 1 cubic foot per second. The theoret- ical floAv of water through nozzles exceeds the figures in table 6 by about 10 percent; allowances have been made for friction losses. The flow through nozzles not shown in the table or for different heads can be cal- culated from the equation :

Q cubic feet per second, A area of nozzle (square feet), /, effective head at nozzle (feet),

(' coefficient of discharge rauRing from 0.8 to 0.94 (usually taken as 0.9, which makes allowance for friction).

To convert cubic feet to gallons multiply by 7.48.

6 Joshua Hendy Iron Works, San Francisco, California.

PLAPKR MINING FOR fJOLD IN CALIFORNIA

[Bull. l:J5

Tnhic .7. Si;ri>, utifihln. and jirirrx of ilouhjc- jointed, linUlirnring giants and deflector a

Giants

Deflectors

w

List

price*

Siie to.

5"? 1

(')

$180

$165

$29.00

Subject to discount because of fluctuations in prices of iron and steel. None required.

Elevators Ruble Elevators

The Ruble elevator is named for the Ruble mine in Josephine County, Ore. It consists essentially of an inclined grizzly on a pitch of about 17", up which the gravel is driven by the stream from a giant. The oversize goes over the grizzly to a ruck pile, and the undersize runs down a chute under the grizzly and thence into sluice boxes, u.sualiy set at right angles to the elevator. The spacing between bars of elevators in use in 1932 ranged from to 2h inches. A 10- or 12-foot apron is used in front of the grizzly. The gravel generally is swept to the foot of the elevator by one giant and through the Ruble by another. The gravel must be washed thoroughly before it is elevated, and the stream of the elevator giant must be used with caution; otherwise, considerable gold may be driven over the top.

Under favorable conditions one giant can handle as much material through the Ruble as another can cut and sweep to it. Under other con- ditions less than half of the material can be put through the Ruble that one giant working steadily can get to it.

Hydraulic Elevators

Hydi-aulic elevators are used to rai.se fvavel. .sand, and water out of placer |)its into sluice boxes. An elevator consists of a pipe with a con- stricted port or throat and a jet which provides a high-velocity ascending column of water. The relative diameter of pi])e. throat, and'jet must be proportioned according to the conditions under which the elevator is used. The elevator may also be used as a water lifter.

Sec. I]

Hydraulic Mining

Tabic 6

Flow of %oa

ter through giants

j 2.

Effective head, feet

Giant no.

a.

H

a.

Is"

2

If

?'

53=i

1,070

1,080

1,090

1,410

1,800

1,330

1,350

1,750

2,210

2,730

J

9 8 30n

1,010

1,280

1,570

1,110 1,120 1,510

1,130

1,520

1,530

1,950

2,550

3,140

1 Adapted from table in catalogr of Joshua Hendy Iron Works, San Francisco, California.

The height to which gravel can be lifted is one-tenth to one-fourth of the effective head of the pressure water at the nozzle of the elevator. Usually the lift will be about one-fifth the head.

The volume of gravel that can be handled by an elevator depends primarily upon the head and volume of pressure water available and to a lesser extent upon the quantity of other water that has to be raised by the elevator. The solids in the water usually are 1.7 to 2.5 percent.

Where little drainage water has to be handled and other conditions are favorable the proportion of the water delivered to the elevator and the giant, respectively, should be about equal, provided the pressure is the same in both. U.sually, however, about twice as much water or a cor- respondingly higher head is required for the elevator. The discharge of the elevator should be high enough to provide dumping ground, other- wise a giant may be needed to stack the tailings. Where plenty of water is available a compound or step-lift elevator may be installed in which one-third of the pressure water is used in the first lift and two-thirds in the second, with a correspondingly larger area of upraise pipe. Thus, the height of the lift may be nearly doubled. Double lifts sometimes are used ; that is, the discharge of one elevator goes to the intake of another.

Placer Mining For Gold In California

[Bull. 135

End section is buitt as separate " " " for moving

Sluice boxes take Solid steel lined floor out from here to here; grizzly above

Pl-AN

Grizzly of 6'

edge, capped witti steel

straps, spaced "

Ftoor steel-lined

Transverse Section Longitudinal Section

36. Ruble elevator used at Redding Creek mine, Douglas City, California.

The elevator discharges upon a cover plate to take the wear in the head of a sluice. Boxes may or may not be used in the pit. The size of the gravel handled is limited by the size of the throat of the elevator. Grizzlies generally are used at the intake. Coarse material reduces the capacity of the elevator; sometimes a Ruble elevator is used in the pit, and only the under-size is sent to the hydraulic elevator.

In clayey ground a hydraulic elevator tends to break up the clay as it goes through the elevator, tluis permitting a higher extraction of the gold.

Gravel pumps have been used successfully in alluvial tin mines and in at least one placer mine in British Columbia." As far as known, they have not been used successfully in placer mining in the Western States.

Hydraulic Mining Practices

Conditions varied widely at the hydraulic mines operated in the Western States in 1932. The practices at these mines illustrate the dif- ferent pha.ses of hydraulic mining and are discussed in this paper. In earlier days, however, when the large hydraulic mines of the West were being worked, more elaborate equipment and larger installations were used than at present. Higher banks were worked, and very large daily yardages were washed, with correspondingly lower costs.

w. . 'Operations of B Boe on Cedar Creek, Quesnel District: Ann. Report of the Minister of Mines of British Columbia. 1932, p. AH2.

Sec. I] HYDRAULIC MINING 109

Gravels

The {Travels being worked at liydraulic placer mines in the summer of 1982 ranged in average depth from 5 to 100 feet ; at Relief Hill, where an old mine was being reopened, the depth was 200 feet. The condition of the gravel ranged from soft, easily washed material to gravels that had to be loosened by blasting. The percentage of boulders over 1 foot in diam- eter ranged from less than 1 to 20. TTsually, 5 to 15 percent of all mate- rial handled consisted of boulders. Boulders up to 20 inches in diameter were put through the sluices. Clay constituted zero to 15 percent of the total material. At. one mine, the Elephant, feet of gravel was over- lain with 40 feet of volcanic ash.

Bedrock at nearly all mines was soft, and the top could be piped off in cleaning up. The slope of the bedrock ranged from inch to 2 inches per foot.

Water Supply

Very few hydraulic mines can operate tlie entire year. Advantage generally is taken of higli-water periods for working the mine. In Cali- fornia the season may begin in November or December, when the winter rains commence, and continue into the dry season of June or July. At most California mines the winter temperature is not low enough to inter- fere seriously with placer operations. Elsewhere in the West, however, hydraulic placer mining must cease with the advent of cold weather in October, November, or December. At such places, work can not begin until spring when the snow melts and the ground thaws. In many local- ities placer mining can be carried on only while the snow is melting on the mountains above during the spring months. The length of the 1932 season at the mines visited by the authors ranged from 25 to 225 days. The precipitation during the winter of 1931-32 was normal or above nor- mal in nearly all districts; immediately preceding years, however, were dry, and the number of days operated at the majority of places was much less than in 1932. In exceedingly dry years some mines do not have enough water to operate at all.

Reservoirs are used at most mines. As the flush supply gives out the water may be stored and used periodically for mining. Usually cutting operations cease when water is not available for piping at least or 2 hours per day. The dwindling supply then will be used for cleaning bedrock and cleaning up the boxes.

Water rights in most of the older placer districts have been adjudi- cated. The rights of some old placer companies are still intact, and the water can be used without hindrance for operating these mines. How- ever, other water rights in streams have been obtained by power or irrigation companies, and water for placer mining must be acquired from those controlling the rights. In some instances, however, water can be appropriated for placer mining.

As stated before, water under a relatively low pressure may be used for undercutting a bank to assist ground sluicing. Generally, however, a head of at least 40 feet must be available for hydraulicking sand and loam and the easiest cutting gravel. An 80- or 90-foot head usually is required to cut average gravel banks. When the gravel is tight or con- tains boulders a head of at least 125 feet should be available for hydrau- licking. For very tight or cemented gravel, heads over 200 feet should be available. Higher heads give greater cutting and driving power to the giants and thus increase production. High pressures are necessary

no

Plackr Mining For Gold In California

Bull. 135

°:

S3

Sq

Se.-

nYOKArijic MiMxr,

Manganese-steel hood-

Fio. 38. Hydraulic elevator.

112 PLAfFR MINING FOR GOLD IX CALIFORNIA . 1

for hirli hanks, as the piants must be set far enougli away tliat caving pravel will not injure the workmen when the banks are undercut. The extreme ran<re of the heads on the jjiants at tlie mines was 40 to 450 feet. The usual ranjie was 100 to 800 feet.

In at least 7") percent of the 40 or more operating hydraulic mines visited in lIKi'i water was conveyed in ditches dug by the early miners. Often, okl pipe lines or salvaged pipe were utilized. Some of the present lines are built of pipe first installed 50 years ago. "Water was pumped at four mines. Pumpinj; water for hydraulicking, however, lias not been generally successful.

The pipe ranged in size from one line with an intake diameter of 46 iiu'hes, wliich was reduced by stages to 24 inches in diameter at the pit, to lines of lO-inch pipe.

Reservoirs where used ranged in size from 0.01 to 15 acre-feet.

Didif of Wafer. The duty of a miiuM-'s inch of water in hydraulick- ing is defined as the number of cubic yards of gravel which it can break down and send through the sluice in 24 hours. The factors atfecting this duty are so varied that it can be compared directly at few mines. An average duty of a miner's inch can not be calculated for the same rea.son. The duty of water appears to be highest in large-scale operations. Tight or cemented gravel is difficult to break down; a high bank takes less pressure water per cubic yard than a low one; a flat bedrock requires an excessive quantity of water for sweeping; angular rock and gravel with flat or large boulders requires more water to move it than does small- size, rounded material ; clay-bound gravels require excessive washing to free the gold; high water pressure is more effective than a low one for cutting or sweeping; and the grade and size of sluices govern the daily yardage that can be washed through them. The calculated duty of water at the mines operating in 10;{2 ranged from 0.4 to 4.3 cubic yards per miner's inch. In these calculations by-wash water is included.

Conditions at the mines range from the most difficult to at least average. Wimnder" reports a duty of as higli as 10 cubic yards per miner's inch at some Alaskan placer mines; the usual range, however, was about 0.5 to 1.7 cubic yards per miner's inch per 24 hours. Piping

After a mine is opened up the gravel bank is undercut by the giant, which allows the overlying material to cave into the pit. The fall breaks the gravel to some extent ; it is further reduced by being played upon by the stream from a giant or by by-wash water. As the gravel is being disinte-rrated it is swej)t by the giant toward the sluice box. Where the gravel is clay-bound or contains lumps or streaks of clay it may be washed back and forth acro.ss the pit bottom one or more times until free from tle clay.

A smaller-diameter nozzle generally is used for cutting than for sweeping. As an example, a quantity of gravel may be brought down wijh a giant witli a 4J-inch nozzle. Then the water will be shut off and a 5-inch nozzle put on the giant for driving the gravel to the sluice, or a separate giant witli a 5-inch nozzle can be used. Usually two or more giants are set up in a pit even when only enough water is available to run one at a time. One large giant will do more work than two small ones using the same quantity of water. The giants are placed at the

''.TlfL'"' ''o'"ian L., Placer-minitiB methods and costs in Alaska: U. S. Bur. Mines Bull. 259, p. 139, 1927.

Sec. I] HYDRAULIC MINING 113

most strategic points both to cut the bank and wash the gravel to the sluice box. Where two giants are used at a time one may be used for cutting and the other for sweeping. The cutting giant is set on an angle to the face. At the old La Grange mine the streams from two 9-inch noz- zles were used together for both cutting and sweeping. Giants may be set up at the lower end of the sluice to stack the coarse material in the tailings where the grade is not sufficient for it to be disposed of naturally.

Sometimes a pit is laid out so that all of the gravel washed in one season is swept to the head of the sluice. After the clean-up the boxes are extended through the washed-out pit and set up for the next year's work. At other places the boxes are extended upward as room is made.

When a pit is started a cut is taken across the channel, after which a diagonal or square face is advanced upstream. In wide channels or bars two or more parallel cuts may be taken. One pit may be worked while boulders are handled or bedrock is cleaned in the other. At the Ruby Creek mine at Atlin, British Columbia, the channel was 250 feet wide; two 125-foot cuts were made and worked alternately. Wing dams of timber, logs, or boulders generally are built to guide the water and gravel into the head of the sluice.

Occasionally the form of the deposit and the contour of the bedrock are such that the gravel is washed over the side of the boxes rather than into the end. Then the sluiceway is sunk into bedrock.

At some mines overburden containing little or no gold may be mined separately. This system has an advantage when dump room at the end of the main sluice is limited, as the higher material may be disposed of elsewhere. At one mine, the Salmon River, the light top material was stripped after the water supply was too low for working the heavier gravels but was still sufficient to supply one giant. The usual practice, however, is to mine the full thickness of gravel at one time. The admix- ture of the top soil and light gravel with the heavier material from near bedrock may permit moving a larger proportion of boulders to the sluice than otherwise.

The number of giants used at one time in the mines operating in 1932 ranged from 1 to 4. The size of the giants ranged from nos. 1 to 6 and the diameter of the nozzles from to 7 inches. A larger nozzle is used for sweeping than for cutting in about half of the mines and the same size in the other half. In one mine, the North Fork placer, water used for sweeping came from a separate source under a lower head ; a smaller nozzle was used than for cutting where the pressure was higher. The nozzles used in the elevators ranged from to 4 inches. The dis- tances that the material was elevated were 25, 44, 54, 17, 30, 9, and 19 feet. The distances the coarse material was elevated by Ruble elevators were 14, 25, and 11 feet.

Handling Boulders

Where the size and grade of sluices permit, all boulders that can be moved by the giant are run through the boxes. As stated before, the upper limit in size at present mines ranged from 4 to 20 inches in diameter. At some of the early-day large producers boulders weighing 3 or 4 tons were successfully put through the sluices.

Lee, C. F., and Daultin, T. M., The .solution of some hydraulic mining problems on Ruby Creek, British Columbia : Am. Inst. Min. Met. Eng. Trans., vol. 55, p. 90, 1917.

eMacDonald, D. F., The Weaverville-Trinity Center gold gravels, Trinity County, Calif. : U. S. Geol. Survey Bull. 430, pp. 48-58, 1910.

I'LACr.R MININC I\)K (;OI,n IN CALIFORNFA

ir.iill. i:}.")

Kic:. V.K IfamlliiiK lioiild.rs witli iliTiick. I'liol,, bi/ C. V. AvrrWl.

Ill <ri-<)iiii(l sliiiciii'-- any Ixiuldo- that can Ix' washed into tlie sluice by the water usually <;<h's throu-ih without trouble. In hydrauliekiiifz', ever, boulders too larjie to run tlii-ouj:li the sluice may be swejit into it with a larti:e j?iaut usiu-r a biih head of water. IJouldei's too lar<i:e to be moved by the j,naut or to run tln-ouih the sluice are handled in various ways, dependiu2: luaiidy upon the nundier and size of the boulders encountered and the nuijrnitude of the operations.

In small-scale operations boulders may be rolled by hand to one side or onto cleaned-U]) bedrock, or (lra;i<ied away by teams. Occasionally, a boidder t(jo larjre to handle may be left standing- on the floor of the pit and bedrock cleaned uj) around it. The usual custom when the proportion of bouhlers is small, however, is to break them up by nutans of hannners or by blasting; and wash the fraiinents throu<:li the sluice. In the larger operations with relatively shallow j:ravel, as at the Salmon Kiver mine, the boulders may be pulled from the pit by wiiu-hes or moved by a derrick mounted on a tractor, as at the Salyer mine. At the Diamond City mine a drag line with an oi-angepeel biu-ket handled boulders very cheaply under the existing coiulitions. A relatively narrow cut was being run. The drag line was operated on a bench above the cut ami i)iled the boulders on the bench back of the drag liiu\ The most connuon nu'thod of handling boulders, howevei', is by means of a derrick. The boulders that can be rolled by hand are loadecl onto a sling or a stone boat and hoisted from the i)it. Large ones are hoisted by means of chains. At some mines few boidders that can not be nuned by the giant are encountered ; derricks are used at tlie liead of the sluice for i-emoving those too large to go through. Stumps are handled in miu-h the sanu manner as boulders.

Cleaning Bedrock

BedrcK'k usually is cleaned by i)i|)ing. As much as 2 feet of bedrock may be cut by the giant and the nuiterial washed through the sluice. Occasionally a fire hose with a small nozzle may be used for the purpose. When the bedrock is hard and contains crevices, it must be cleaned by

See. I] HYDRAULIC MINING 115

hand. The crevices and soft scams are dug out by means of small, flat tools made for the purpose.

Sluice- Boxes and Riffles

Sluice-boxes were laid on bedrock at the most of the mines being operated in 1932. At a few, where high chauuels were being worked, cuts had been run to bedrock to permit an adecpuite grade for the sluices. In one mine, a tunnel was used.

Individual boxes were 12 feet long at the majority of places. In a few districts 16-foot boxes were jireferred, and occasionally a 10- or 14- foot box was used. The higtli of the sluice at various mines ranged from 32 to 5,000 feet. The long sluices generally are used only wlien they are necessary as tailraces. The width of sluice boxes at these mines ranged from 12 to 60 inches. The extreme range in the grade of boxes was from l inch to inches to the foot (1.0 to 12.5 percent) . The n.sual range Avas from ] to inch to the foot (2.1 to 6.2 percent).

Riffles serve a twofold purpose, they pi-otect the bottom of the sluice and catch the gold. Both strength and wearing qualities are required in large-scale liydraulic operations where boulders up to a ton in weight may be put through the boxes. AVooden blocks, rails, rock paving, and iron castings, in the order named, were used at the larger mines operated in 1932. When the service was not so severe, poles, angle iron, and Ilun- garian-type riffles were Used. The Hungarian riffles usually were made of wood and were protected from wear on top by strap iron.

At all mines most of the gold was caught in the first few boxes of the sluice. The top boxes were cleaned up twice a season, monthly, weekly, or even oftener. In long sluices the lower boxes were cleaned only at the end of the season or when repairs were needed. At the time of the gen- eral cleanup worn riffles were replaced and the sluices repaired if neces- sary. Quicksilver was used in the sluices at the largest mines, but at the majority it was used only in cleaning up.

Although the sluice is an efficient gold-saving device some gold gets away, especially- if the gold is very fine and the gravel carries a relatively large proportion of black sand. To further recover the gold, undercur- rents were used at 10 mines. The term "undercurrent" in placer min- ing is used to designate a device for catching the gold contained in the fine material drawn out through a grizzly in the bottom of the sluice. The undercurrent usually is placed near the lower end of the .sluice. At most mines it is not possible to draw all of the material small enough to go through the grizzly to the undercurrent, as not enough water would be left in the sluice to dispose of the coarse material. The quantity drawn off is controlled by the area of the grizzly and the openings between the bars. The grizzly bars are i, ], iJ, 5, or 1] inches apart. Undercur- rent boxes, or tables as they are sometimes called, are relatively wide to permit a shallow depth of the .sands.

The same type of riffle generally is u.sed on undercurrents as in sluices where a screened product is treated. Hungarian riffles, usually similar to those used on dredges, Avere favored. Steel matting or wire screen over burlap was used at two mines ; planks with holes bored in them, angle iron, and stone paving were used at one mine each ; and a variety of riffles was used at another mine (Salyer). Quicksilver was used on undercurrents at nearly all of them. An important function of an undercurrent in placers where quicksilver is used in the main sluice is

pi.A( i:h minin(; for r.oi.n in cai.tfornia [Bull. 135

,S-

V 3w-

P'iG. -JO. Sluif.' box at liyilraulio mine, /'/lo/o (j.i/ C. V. A\*riU.

Fig. 41. P'orkiUK Ij-.ul.leis along sluice at hydraulic mine. Photo by courtesy of Roy McGain; reprinted from California Joiii-nal of Mines and Geology, October 19il, p. 5H.

Sec. 1 1

Hydraulic Mining

Fig. 42. Stacking coarse tailing with giant; .sluice i.s under grizzly. Reprinted from California Journal of Mines and Geology, January 19.il, p. 50.

to catch quicksilver or balls of amalgam that may get away in the sluice. As much as 10 percent of the recovered gold may be saved' on the under- current, but in most places less than 5 percent is so obtained. At three mines where an estimate Avas made, 3, 5, and 8 percent, respectively, of the total gold recovered was saved on the undercurrent. At two places so little gold reached the undercurrents that they were not cleaned up at the end of the 1932 season.

The sluice-box serves a double purpose in placer mining ; it collects the gold or other heavy minerals sought within the riffles of the sluice and conveys the washed material to a dumping ground. It is an efficient gold saver and is universally used in hydraulicking and ground-sluicing. The principle of the riffled sluice is used for recovering most of the gold on dredges and in other forms of placer mining where the gravels are excavated mechanically.

Sluices are built in accordance with the service to be demanded of them. Riffles are of varied forms and are made of different materials. Although the form of riffle is chosen largely to fit particular conditions custom in various districts and materials at hand have a bearing upon the practices followed.

The following discussion has a general application and is not con- fined to any region or method of mining.

Construction of Sluice-Boxes

Sluice-boxes are rectangular in section and are nearly always built of lumber ; steel or iron sluices, however, were used at a few washing plants operated in 1932. The construction of a wooden sluice-box depends somewhat upon the size and service expected of the box; a number of types, however, may be used satisfactorily.

The important features in design a-e .sturdiness and .simplicity of construction. Large flumes may have to with.stand severe battering and vibration from the passage of heavy boulders, hence they must be strongly constructed and well braced. In small flumes this feature is less impor-

118 rLACKK MININc; FOK COLD I.V CAMFOKNIV [. 135

tiiiit. I)iit the Mso of li'litcr linnl)or iiicrcnscs tlio (liniciiltics of iiuiintoiiaiice and pi'cvciitidii of leaks.

'I'lic bottom of a iiari'ow sliiico sliould he a sinjrlo ])lank if lumber of tlic desired width is obtainable; for widei- boxes two or more bottom planks must be nsed. The bottom joints may be made tijrht by the use of soft-pine splines, by batten strips nailed on the outside, or by caulkinj with oakum or other material, liowie'" i-econnnends half-seasoned lum- ber as most suitable for the construction of boxes. AVIiere local timber is used it is common jiractice to cufthe plaidv durinj; the dry season or before snow is off the jrround. It is not customary to use surfaced lum- ber for boxes, althou<rh a smooth bottom facilitates the clean-up. The lumber slunild be cleai- and of uniform si/e.

For any but small, tempoi-ary installations the sides of shiice-boxes should be lined with a wearing- surface of r()U<zli lumber or sheet iron. Otherwise the entire box must be replaced when the sides are worn out. Board lininfr is easier to place and replace than sheet iron. In early Californian practice some of the side lininjis were made of wide, thin blocks nailed on so as to present the endjirain to tlie wear. Worn iron or steel riffles are used for side lininj; at some places. Usually only the lower half or third of the side of the box needs tliis proteetion, and a siufrle 2-ineh board may serve not only for lininu- but as a cleat to hold down the i-iffles. False bottoms of planed or rou<ih boards may be used to save wear on the box proper.

Each box should rest on three or four sills, efpially spaced. The sills and uprifilit nuMubers at the ends of the box serve as battens to prevent leakajre at joints. The practice of taperin<r the box enoujrh to permit a telescope joint is very convenient in small sluices, especially if the boxes must be moved occasionally. Small, three-board boxes may be braced with tie>i across the top, although this hampers shoveling: and clean-up operations. Larjrer boxes sliould be braced externally from the ends of the sills. Sills should be weifihted with rocks to check any tendency of the sluice to rise. If the sluice is placed in a bedrock or other cut, water under it or at the sides has a strong: lifting- effect. Moreover, the vibra- tion caused by boulders rolling- throu<ih the sluice permits fine prravel to be washed under the sills placed on the ground.

As mentioned, the side lining: plaid< may serve as a cleat under which the riffle sections can be wedged to the bottom of the sluice. Otherw'ise some other i)rovision nnist be made as the riffles must be held securely. In small boxes it is customary to lay long:, narrow boards on edge on top of the riffles and against the sides of the sluice. These boards are 'wedged down tightly under cleats nailed i)ermanently to the sides of the box. The practice of nailing riffles to the bottom of the box, or using any device that recjuires driving luiils in the bottom or sides, should be avoided as it results in leaks and eventually damages both sluice and riffles. Wooden blocks are the most diflicult to secure in place but can be held by the method described in the following section. Rock pavement dejiends on its weight, on being packed tightly, antl sometimes on the slight down- stream tilt of the individual stones to resist the shifting action of the current. Maintenance of Sluice-Boxes

Maintenance work on sluice-boxes consists chiefly in aligning and bi-inging to gi-ade any boxes that have moved out of position, replacing

'" MowU-. A. .1.. Il.\<lr;uili<' niiniiij; in :ilif..riiia, lid t<l.. p. 22<i, .Vt-w Vf.rk, Van N'o.strand Compuny, 18S!t.

S(

iiydrai'i.k: minixo

liiiinjis, and plujr<iiii<>' leaks. Attoiition to this work at clean-up time will be re])ai(l by {greater (ai)acity and fi-cedoni fi-oni break-downs when the water ajiain is turned into the sluice.

Size

As pre\iously shown, sluice-box(>s seldom are built less than 10 inches wide for strictly mining pui-poses. Eijrht-inch boxes, liowever, may be used in sampiin' or clcaniufr up. The (piantity of water, with its accom- panyinjr load of <:i'avel, that will run tlu'ourh a sluice of a p:iven size depends upon a number of factors. The practice at the majority of about 75 hydraulic and jrround-sluice mines visited in the preparation of this paper indicates that the carryinji' capacities of sluices of various widths are within the followino: limits:

Width of box, inches

Miner's inches of water

From

To

12 - .

1,000

48 to 60

These limits probabh' represent good practice.

]\Iore trouble is experienced from clogging: of boxes that are too. wide, because tlie depth and velocity of water are insuicient, than from failure of boxes to carry their load because they are too narrow.

The current velocities required to transport different sizes of mate- rial have been studied ; works of various authorities are cited by Gilbert." The following table is based chiefly on Dubuat's figures for competent velocity ; the figures are adjusted to approximate mean velocity instead of bed velocity. The last three figures are taken from Van Wagenen."*

Size of material moved

Mean velocity,

approximate feet

per second

Sand:

Fine

Coarse

Gravel:

Fine

1-inch

Egg-size

Boulders:

3- and 4-inch 6- to 8-inch-. 12- to 18-inch

"Gilbert. G. K., The tran.'portation of debri.s by running water: U. S. Geol. Survey Prof. Paper S(i, p. 216, 1914.

'2 Van Wagenen, T. F., Manual of hydraulic mining, p. 88, New York, Van Nos- trand Company, 1880. ''

120 I'LACKK MININC. FOK COM) IN (Al.IFORNIA [Bull. 135

WfllrouiKlcd pebbles are easier to move tlian angular ones, and rock of low specific <:ravity' is appreciably easier to wash than heavy, dense rock such as <rreenstone or basalt.

({old ha.s a better opportunity to settle and be cauf?ht in riffles in a wide, shallow stream than in a deeper and narrower stream of the same volume; the wider sluice, however, usually nnist be set on a steeper grade.

Small- or medium-size boxes generally are roujrhly square in cross- section ; larpre bo.xes iisually are one-half to two-thirds as deep as they are wide. The water in a sluice should always be more than deep enough to cover the larp-est boulder that may be sent throujrh. In practice, the depth of the stream in the main sluice at hydraulic mines usually is a fifth to a half the width of the box so as to prevent spills if the box is tempo- rarily plufTfed by boulders or sand. Where screened prravel is being washed, as in undercurrents or on dredges, wude and shallow .streams are necessary for the recovery of fine gold. In "booming" operations the boxes usually are run full in order to handle the relatively large volumes of water that fiow for .short periods only, and the sluices commonly are about as deep as they are wide. It would be desirable but impracticable to decrease the depth of water by using wider sluices, as flows of 5,000 to 10,000 miner's inches are not unusual when the gate of the reservoir sud- denly is opened wide.

Grade of Sluice

Usually the grade of the sluice depends upon the slope and contour of the bedrock. If the gradient of bedrock, however, is too low to permit sufficient fall for the sluice, cuts or tunnels may be run in the bedrock to overcome this difficulty, 'ery short sluices of only 1 or 2 boxes some- times are set nearly flat where there is a drop at the end of the box, the gravel being forced through the sluice by the initial velocity and the head of water in the pit.

The opinion of most operators is that about 6 inches in 12 feet is the best grade for average conditions. Grades as flat as 3 inches in 16 feet can be used but only at great loss of capacity. At the Depot Hill mine, where a grade of 3 inches in 14 feet is used, all rocks over 5 to 6 inches in diameter must be left in the pit. Because of the greater friction and the consequent lowering of velocity, steeper grades are needed for small sluices: than for large ones; some operators favor grades of 12 inches to 12-foot box. For maximum gold-saving efficiency, as well as for economy in the dump room, grades should be as flat as possible without lowering the velocity to such an extent that the riffles pack with sand. Any increa.se in slope from that adjustment will increase the capacity of the sluice, increase the wear on the sluice, and decrease the efficiency of the riffles, resulting in gold losses if carried to extremes or if the gold is very fine. If water is scai'ce. gold recovery may well be sacrificed to capacity. Bowie " states that grades of 10 to 24 inches were used in some Forest Hill Divide (California) mines for this reason. Increasing the propor- tion of water to solids decreases the tendency of riffles to pack with sand.

Sluice capacity increases with grade but more rapidly ; that is, dou- bling the grade of sluice boxes will more than double the quantity of gravel that can be put through the boxes by a given flow of water. The absolute increase cannot be predicted closely as coarseness of gravel,

" Bowie, A. .1., A practical treatise on h>draulic mining' in California, 3d ed., p. 220. New Yorit. Van Nostrand Company, 1889.

Sec. T] HYnRAUiiic minino 121

velocity, and shape of the box appear to have some beariiif? on the relation of capacity to slope. F'or instance, Bowie " cites a mine at which chang- ing the grade from 8 to inches in 16 feet increased the quantity of gravel sluiced through the same boxes with the same flow of water by about one-third.

The established grade should not be decreased anywhere along a sluice, otherwise gravel may accumulate where the current loses velocity. If the water and gravel, however, enter the first box with considerable speed, say, from the discharge of a hydraulic elevator, the first boxes may be placed on less than the regular grade. Bends or curves are undesir- able as they complicate construction and induce clogging and running over. When a curve is unavoidable it should be as gradual as possible, the outside of the sluice should be elevated a fraction of an inch, and the grade should be increased perhaps an inch per box at and immediately below the curve. Similar rules apply to turn-outs or branches, and drops of 3 to 4 inches should be provided at junctions to check the deposition of grarel at these points. Such drops occasionally are inserted in straight sluices if the grade is available, particularly if the gravel is a difficult one to wash or if heavy sand tends to settle to the bottom. A drop of even a few inches from one box to the next has a disintegrating effect and mixes the material passing through the sluice, thus assisting gold recov- ery. At one place where drops were provided at intervals between dif- ferent types of riffles, 25 percent of the gold recovered in the sluice was found at the drops."

Theory of Gold-Saving by Riffles

The function of riffles is to hold back the gold particles that have settled to the bottom of a flowing .stream of water and gravel. Any ' ' dead ' ' space in the bottom of a sluice-box, where there is no current, fills quickly with sand and thereupon loses most of its value as a gold saver, unless the sand remains loase enough to permit gold to settle into it ; therefore, the shape of riffles is important, regardless of the fact that under some conditions, as with coarse gold and free-washing gravel, all forms of riffles are almost equally efficient. The riffles should be shaped so as to agitate the passing current and produce a moderately strong eddy or "boil" in the space behind or below it, thus preventing sand from settling there and at the same time holding the gold from sliding farther down the sluice. In other words, riffles, for maximum efficiency, should provide a rough bottom that will disturb the even flow of sand and gravel, will retain the gold, and will not become packed with sand. Where grade is lacking the riffles must be relatively smooth, so as not to retard the current unduly ; under these conditions the sluice must be long enough to compensate for the loss in gold-saving efficiency of the individual riffles.

Natural stream beds act as gold-saving .sluices, not because they are particularly efficient as such but because most gold is "hard to lose" and the streams are long.

isTheller J H, Hydraulicking on the Klamath River: Mm. and Sci. Press, voL 108, pp. 523-526, March 28, 1914.

1T.A( KH MIN'INC row fiOI.n IN CAI.IKOHNIA

|i;uii.i:!5

Cd

o

z

h

k

N

W

/Or/ -s±/

H

V Q.

/;

V Jl' -/ 7/

n a

o

y

/ H

lO

/

r 1

r

fw/

)7

' O

z

//

z

//

/.

r —

/

7 /

ifi

/ /

o

z

M

//

J

/ / /

a.

ri

z

A

w

M

/

z

le

///

(0

&

y // y / y yy y yy / /

ul

/ / y £ J

iUi'li

/ A / Jy

yy y / y yy y yy / /

o

/

a

u

m

P

W////a

V /uP

z o

\///

'J-i*

u

/ V

in tn

u

-l

See. I] IlYDHAfMC MIMNC 123

Types of Riffles

l\iffl(>s, (if ((iiirsc, should he designed so ;is lo sjivc llic fold under tlic existiii<r conditions. Tlioy should niso he chcfip, durahh', find easy to place and remove. Not all tiies(> (pialities ai'c rounil in any one type.

Sluice-box i-iffles may ])o classificMl rou<.ildy as transverse, lon<iitu- dinal, block, blaidcet. and misccllaneou.s i-ously surfaced ones, oi*. accord- ing; to material, as wood block, i)ole, stone, cast iron, rail, anle ii'on, fab- ric, and miscellaneous. Tsually more than one type of liftle is used, althou<:li in California very lon' sluices- have been paved entirely with wood-block riffles.

Of about 80 hydraulic, jii-ound-sluice. and mechanically worked placer mines visited in 1!>:2 by the authors, ajjproximately 25 percent used riffles of the transverse variety, loosely termed "llunjarian," con- sistiufj generally of wooden crossbars fixed in a frame and sometimes capped with iron sti-aps. About 20 percent used the lonjiitudinal pole type, 15 percent wooden blocks, and 15 ])ercent i-ails, the last being placed crosswise or lengthwise. Angle-iron riffles, wire-mesh screen or expanded metal on carpet, blankets, or burlaj), rock paving, and cast-iron sections together made uji the i-emaining 25 percent. The oidy general rule observed was that the size of the riffles was roughly proportional to the size of the material to be handled and that for fine material, particu- larly the screened gi-avel washed in most of the mechanically operated plants, the di-edge-type riffle found most favoi-.

For a small or medium-size sluice (if luiidjer is costly and a plentiful supply of small timber, such as the lodge-pole pine so connnon in many Western States, is available) peeled pole riffles are perhaps the most eco- nomical and satisfactory of the various types. Those of transverse vari- ety may have a somewhat higher gold-saving efficiency, but undoubtedly they retard the current more and wear out faster. Poles 2 to 6 inches in diameter may be used, spaced 1 or 2 inches apart. Such i-iffles are cheap but wear out rapidly. The sections should be a third or half the box length for convenience and 1 or 2 inches narrower than the sluice. At the Golden Rule mine 6-inch pole riffles had to be replaced every 10 days or after each 1.200 cubic yards had been sluiced. The sluice was 30 inches wide and had a grade of 8 inches in 12 feet. At other mines poles last several times as long.

If sawed lumber can be obtained cheaply, riffles similar to the one de.scribed may be made of 1- by 2-, 2- by 2-, or 2- by 4-inch material. The top surfaces of the riffles may be plated with strap iron. Transverse riffles of this type may be slanted downstream and the top surfaces may be beveled to increase the "boiling" action, as with the dredge riffles. The effectiveness of this practice is not known, and the authors know of no conclusive tests having been made. Longitudinal riffles of 2- by 4-, 3- by 4-, or 2- by 6-inch material are used at some ])Iaces.

Wooden-block riffles are held by P.owie'*' to be unexcelled in regions where the material is available cheap. The blocks are 4 to 12 inches thick and of corresponding diameters or widths. They may be round, partly squared, or cut from square timber. One- or two-inch wooden strips separate the rows of blocks, and they are held securely in place by nails driven in both directions. "Wooden-block riffles are perhajjs the hardest of all types to set because of their tendency to float away. They

Bowie, A. J., op. cit., p. 225.

124 PLAf'KR MININ'O FOR OOLD IN CAI.IFORNIA [Rull. 135

must be nailed to the spaeinjr strips, as stated, and \vedpred seenrely at the sides. The spaeiii}; strips are held down at either end by the side linint; of the sluice. Wooden-bloek riffles are durable, ean be worn down to half their ori'inal thickness or less, and if made of lonjr-frrained wood (such as pitch pine, which "broom?." instead of wearing; smooth) may catdi .some jrold in the end'rain. When discarded, they arc commonly burned and the ashes panned to recover any rold so caujrht. The life of 10- or r2-inch wooden-blo'-k riffles may be a few months to several sea- sons and, aecordinfr to Bowie, ranfjes from 10(),0()() to 2()(),00() miner's inches of water; that is, with a flow of 1,000 inches one would last 100 to 200 days. The grade of the sluice apparently has much to do with the life of block riffles. At the Superior min' where the sluice was 48 inches wide and had a grade of 21 inches in 12 feet a set of blocks lasted two sea- sons, during which time 140,000 cubic yards was sluiced. At the Salmon River mine the grade was 7 inches in 12 feet and the width of the boxes .30 inches. Here block riffles la.sted 60 to 70 days, during which time about 18.000 cubic yards was washed. On account of differences in the wear- ing rates only one variety of wood should be used in a section of a sluice, Douglas fir wears longer than other native western conifers.

Stone riffles are durable and fair gold catchers. Stones ranging from the size of cobbles to 8 or 10 inches in diameter are packed closely on the bottom of the sluice. They may be held at intervals of a few feet by transverse wooden strips. In some instances the stones are roughly hand-shaped and set similarly to street paving. Stone riffles are difficult to set and generally are not used in portions of a sluice that are cleaned up frequently. Their main advantage is their long life. Because of their roughness, stone riffles require a steeper slope than wood blocks, a feature that sometimes would prohibit their use.

Where large quantities of gravel are put through sluices, iron or steel riffles generally are preferred. Their superior wearing quality as compared with that of wood permits longer runs without stopping to replace the riffles. Their durability may more than compensate for their higher cost.

Steel rails and angle iron are common riffle materials used in various ways. Old rails or angle iron can often be obtained cheaply in mining districts or near railroads. Various other steel products such as pipe and channels have been utilized for riffles. Cast iron is also used and has the advantage of a lower first cosi than steel rail or angle iron.

Iron or steel riffles should not be used in units too long to be handled readily. Rope blocks on movable tripods have found favor at some places for lifting heavy riffle sections.

When used as transverse riffles lengths of steel rail usually are set upright, the flanges almost touching or not more than 1 or 2 inches apart. Where grade is lacking and gold saving is not particularly difficult, longi- tudinal rail riffles make excellent paving for a sluice as they provide a smooth-sliding bottom for the gravel and boulders. The rails ordinarily are bolted together by tierods passing through wood, pipe, or cast-iron spacing blocks, forming riffle sections the width of the sluice and any con- venient length. At La Grange mine in Trinity County, California, 40- pound rails costing about $125 per ton proved more satisfactory than wood riffles.' When 16- by 16- by 13-inch wood blocks were used the

"MacDojnald. D. F., op. clt.

Sec. I] HYDRAULIC MINING 125

riffles tended to "sand up." Moreover, the blocks had to be replaced every 2 or 3 weeks. Leno:th\vise rails 8 inches apart lasted 2 months and rails 5 inches apart, 4 months. Strangely enough, transverse rails 5 inches apart lasted 6 months. The rails were spaced by cast-iron lugs and set right side up on timber sills. When the head of the rail was worn off the remainder was used for side lining. This sluice was handling a flow of about 4,000 inches of water and 1,000 cubic yards of material per hour, boulders as large as 7 tons being washed through. The eddies behind the rails were believed to be the cause of the improved recovery as compared with that using block riffles. The lower part of the branch- ing sluice line was cleaned up every other season only. The combina- tion of steel rails and wooden sills used at La Grange mine appears to make an excellent gold saver, and modifications have been used at many large mines.

Angle iron is commonly used for making riffles. Many methods of assembling the lengths of angle iron into riffle sections are in use, and no one method can be said to excel. The irons may be set with flat upper surfaces or inclined slightly to increase the riffling action. Usually the gap between the riffle bars is to 1 inch. The effectiveness of this type of riffle is believed by some operators to depend largely on the vibration of the riffles under the impact of boulders, which keeps the sand trapped under the angles in a loose condition favorable to gold saving.

Cast-iron riffles of all shapes and sizes have been used. If available at low cost they are very economical, as they wear slowly, can be quickly and securely placed, and are efficient gold savers if designed so as not to pack with sand. In an undercurrent at the Indian Hill mine, California, cast-iron riffles were in use that were 4 feet long, shaped like angle irons, and had equal 3|-inch legs inch thick.

For shallow sluice streams carrying only fine material various gold- saving materials are used, including brussels carpet, coco matting, cor- duroy, and burlap. These may be held down by cleats or by wire screen. Fabrics often are used in combination with riffles to catch fine gold and hinder its being washed out of the riffles by eddies. A corduroy woven specially for a riffle surface is used by some large Canadian lode-gold mines to catch their "coarse" gold before flotation or cyanidation. As such gold would be considered fine by most placer miners it seems prob- able that such a fabric would be useful for treating finely screened placer sands. The corduroy in question has piles about inch wide and inch high, spaced about inch apart. The piles are beveled slightly on one side. The cost in Canada is about $1.00 per square yard.

Heavy wire screen such as that used for screening gravel makes an excellent riffle for fine or medium-size gravel in fairly shallow sluice streams, and generally it is used with burlap or other fabric underneath.

Expanded metal lathing and woven metal matting are common types of riffles for fine material and are used with carpet or burlap. If the thin strands of metal slant considerably in one direction, the material should be placed with this direction downstream. Eddies in back of the strands will then form gold catchers, whereas if the recesses face upstream they will at once fill with a tight bed of sand and lose their effectiveness.

Solid-rubber riffles were noted at one washing plant. Sponge-rubber riffle material is on the market, but it was not observed in use and nothing is known by the authors of its merits or cost.

PLACER MINING FOR GOLD IN CALIFORNIA [Bull, lo")

Kin. -M. LMokniK down ff.iii hillsulc ;U sluic- and undercurrents. Lower end of sluiie is in center t)f photo. Reprinted from California Journal of Mines and Genlofjjj, January I'Jil, p. 61.

Sec. I] IIYDHAULIC MININO 127

Anotlier form of riffle often used as An auxiliary to otlier types is a mercury trap, consisting of a board the full width of tlie sluice with 1- or li-inch auj>er lioles in which mercury is placed. Instead of round lioles, transverse }i:r()oves or lialf-moon-sluiped depressions, 2 to 4 indies wide and with tiie rouiuled, deep side downstream, may be cut in a wide board and partly filled with mercury. These riffles have no apparent advantage over tlie ordiiuiry transverse-bar type and ai-e suitable only for fine gravel, as lai-ge pebbles would sj)lash the mercury out of the traps.

Many ingenious and odd kinds of riffles ai'c encountered in the field, some of which have been i)atente(l. It is veiy uidikely, however, that the advantage of any unusual oi- freakish design of i-iffle is sufficient to offset the cost of I'oyalties on patented inventions.

Undercurrents

An undercurrent, as dcfiiu'd before, is a device for sluicing sepa- rately a finer part of the gravel ])assing through the nuiin sluice. The fine material and a i-egulatcd (luantity of watei- i)ass through a stationary grizzly in the bottom and usually near the end of the sluice to one or more wide sluice-boxes, connnoidy called tables, paved with suitable riffles. If the main sluice is in sections, with drops between, the water and sand may be returned from the undercurrent tables to the main stream, and several undercurrents may be installed at convenient points along a sluice.

The sci-een or grizzly in the main sluice may present the most diffi- cult problem in building a satisfactory undercurrent. The screen should divert all the undersize yet not take so much water that it causes plugging of the main .sluice below the undercurrent. The proper size of opening can be determined oidy by experiment. A screened or barred opening, tiie full width of the main sluice and a few inches to a foot or more long, will usually draw off as much water as can be spared. New water may be added to either the undercurrent or main sluice if the screen opening does not take out the right (piantity for successful operation. Usually minus to l-inch material is desired for the undercurrent, and either punched-plate screen or iron-bar gi-izzlies may be used to make the separa- tion. Grizzlies should be made of tapered bars or screens i)unched with tapered holes with the largest openings downward, otherwise they will plug and render the undercurrent iiieffective.

Because undercurrents need a wide, shallow .stream, grades of 12 to 18 inches per 12 feet must be used, depending largely on the type of riffle. Cobblestone, block, tran.sverse or longitudinal wooden strips, rails, screens, or fabrics may be used for riffles. Often several types of riffles are used on successive parts of one undercurrent. Undercurrents may be a few to 25 or 30 feet wide and 10 to ;")() feet long

Most of the gold recovered by undercurrents is so fine that it does not settle in the relatively swift, deep current of the main sluice, but part consists of gold that is freed from its matrix of clay by dropping through the grizzly and rolling over the uiulercurrent riffles. All coarse gold is saved in the first few boxes of the main sluice \ndess conditions are radically wrong. Unless the undercurrent is installed at the end of the sluice, or at least below where gold is recovered, not all the saving in the undercurrent .should be credited to its installation. In the early daA's when hydraulicking Avas at its height undercurrents were much favored, sometimes 5,000 to 10,000 square feet of undercurrent being used

128 place:r minino for oold in California [Bull. 135

along a single sluice line. The gold saved in them occasionally exceeded 10 percent of the total clean-up but more often was less than 5 percent. As this recovery usually was effected by 5 or 10 large tables and as con- siderable would have been saved by the main sluice without the under- currents, the economy resulting from their use was perhaps doubtful. Bowie'® presents details of the use of undercurrents in early Californian practice and indicates that their particular field lay in the treatment of cement gravels. Of the several undercurrents observed by the authors in use in 1932 it is doubtful if many were justifying their installation.

Operation of Sluice- Boxes

Under favorable conditions a properly designed and constructed sluice-box requires little attention other than periodic clean-ups and nrinor repairs which are made at the same time. Unfortunately, such a combination rarely occurs, and an appreciable part of the miner's operating expense is chargeable to work along the sluice lines.

The best results are obtained when a steady flow of water and gravel passes through the sluice. An excessive flow of clear water through the sluice will bare the riffles, causing some gold to be lost. On the other hand, a continued overload of gravel will plug the sluice at some point so that sluicing must be stopped for the time needed to clear the obstruc- tion ; this time lost may be appreciable. If plugging can not be prevented by increasing the grade or the flow of water or reducing the feed, one or more sluice tenders must work along the sluice with forks or shovels to keep it open. This added cost may be serious at small mines. All effort should be directed toward getting the gravel into the box and letting the water do the rest.

Large boulders are another cause of expense and lost time. "When the maximum size of boulder that the sluice will carry is known, all boulders larger than this should be prevented from entering the boxes. Relatively little work directed to this end will save hours of delay in clearing plugged sluices and unnecessary wear and tear on the boxes and riffles.

An exception is found in the operation of "booming." A necessary condition of this work is a heavy head of water which usuallr fills the sluice to the brim. Sometimes little or no work can be done in the pit while the water is on, and the entire crew may profitably patrol the sluice with long-handled shovels to guard against stoppages which might be disastrous becau.se of the large flow of water and gravel. Before each "boom" all oversize boulders should be moved out of the course of the water.

Cleaning Up

Clean-up time should be kept to a minimum. This can be done by cleaning up as seldom as practicable and by using efficient methods. Large hydraulic mines, particularly if the water season is short, clean up only once a season except perhaps the upper one or two boxes. Dredges clean up every 10 days or 2 weeks, because large amounts of gold are recovered in relatively short sluices with attendant possible loss when the upper riffles become heavily charged. This necessary delay is used for routine repairs on the dredge. In ground-sluicing the clean-up period ranges from weeks to months, while in shoveling-in operations the sluice

"Bowie, A. J., op. clt., pp. 252-262.

Sec. I] HYDRAULIC MINING 129

may be partially cleaned up daily. The danger of theft from the upper, richer boxes can be lessened by filling them with gravel at the end of each day's work.

The general principle is the same in all clean-up operations, but practice differs widel}'. Clear water is run through the sluice until the riffles are bare, the stream being reduced enough to prevent washing out the gold. Then the water is turned off or reduced to a very small flow, and the riffles of the first box are lifted, washed carefully into the box, and set aside. Any burlap or other fabrie used under the riffles likewise is taken up, rinsed into the box, or placed in a tub of water where it can be thoroughly scrubbed. Then the contents of the sluice are shoveled to the head of the box and "streamed down" with a light flow of water. The light sand is washed away, and rocks and pebbles are forked out by hand. This operation is repeated until the concentrates are reduced to the desired degree of richness. Gold or amalgam may be scooped up, as it lags behind the lightest material at this stage, or all the black sand with the gold, mercury, and amalgam may be removed and set aside for further treatment. Successive boxes are treated similarly, until the sluice is bare. The last step is to work over the whole sluice with brushes and scrapers to recover gold and amalgam caught in cracks, nail holes, or corners. At the Wisconsin mine a small box was set up in the main sluice and the concentrate from the riffles shoveled into it to reduce the bulk. At the Round Mountain mine the concentrate from the lower section of the sluice was treated in a quartz mill.

Use of Quicksilver in Sluicing

Quicksilver is used at nearly all placer mines. If it is not used to catch gold in the sluices at least it is probably used in extracting the gold from the concentrates. The average market price for mercury in 1932 was about $58 per 76-pound flask, but quicksilver purchased in 5- or 10-pound lots from a chemical-supply house cost about $1 per pound. Except in districts where placer mining was particularly active, drug stores or other local retailers charged about double this amount. The price in January 1934 was $67.54 per flask, and in late 1945 was $106 per flask.

The characteristics of quicksilver that make it of value to the miner are: (1) Its power of amalgamating with gold and silver; (2) its high specific gravit}' (13.5), which causes it to lie safely under a stream of water and gravel, floating off on its surface everything but the native metals ; and (3) its relatively low boiling point (about 675° F.) far below red heat, which allows it to be driven off by heat from the gold with which it has amalgamated.

Amalgamation is a process in which mercury alloys with another metal. All metals but iron and platinum amalgamate more or less readily. Clean and coarse placer gold alloys readily, but if the gold is partly coated with iron oxide or other substances (for example, "rusty" gold) it amal- gamates Avith difficulty. The mercury itself should be clean enough to present a smooth, shiny surface ; the presence of some gold or silver in the quicksilver, however, is said to facilitate amalgamation, that is, to make it more "active."

Quicksilver is placed carefully in the sluice-boxes, where it finds its way to the many recesses in the riffles and lies in scattered pools, ready to seize and hold any particle of gold that touches it. It is used in this

9 — 56968

130 PLACER MINING FOR OOLD IN CALIFORNIA [Bull. 135

manner in almost all important liydraulic operations, but some operators place it in the boxes only shortly before the clean-up, evidently believing that the added gold saved by its use during sluicing does not compensate for the loss of the mercury that passes through the sluice with the tailings or escapes through cracks or other leaks. In exceptional instances the conditions are such that the mercury ' ' flours, ' ' that is, breaks into minute, dull-coated drops. Flouring is aggravated by agitation or exposure of the mercury to air. The common practice of "sprinkling" it into sluice boxes may be condemned on this ground, as well as for the reason given by Bowie*" that the fine particles formed by careless sprinkling are more readily washed away and lost. F'louring is responsible for the most serious losses of quicksilver with the tailings.

Even under the best conditions, 5 to 10 percent of the mercury used is lost. If steep grades, heavy gravel with consequent severe pounding and vibration, old and leaky sluices, or other adverse conditions exist, the loss of mercury may be 20 or 25 percent.

Only clean mercuO' should be placed in a sluice; even this tends to become fouled or sluggish and to lose its effectiveness. The best cleansing process is retorting, which is discussed later. However, straining the mercury through chamois or tightly woven cloth removes some of the surface scum and foreign material, or the mercury may be treated with potassium cyanide or other chemicals to dissolve the impurities. It should be handled as little as possible and kept from contact with grease or other organic material.

Wilson-" suggests a cow's horn, sawed off near the small end to leave a hole that can be stopped with the finger, as a useful implement for charging sluices. Most miners charge the sluice from stoneware or heavy glass bottles such as are used for champagne.

Mercury should be kept or carried only in iron, glass, or earthenware containers because of its tendency to amalgamate with zinc (galvanized iron), tin, or other metals.

The quantity of ([uicksilver used differs according to conditions and custom. According to Bowie,-' 200 or 300 feet of 6-foot sluice should receive about three flasks (225 pounds) as a first charge and a 24-foot square undercurrent, 80 or 90 pounds. At the Depot Hill mine one flask is placed in the first four or five boxes each month during the washing season. At another mine two flasks were used in a season during which 100,000 cubic yards was washed. Dredge tables, with areas of 1,000 to 10,000 square feet, are charged with 150 to 3,000 pounds of mercury. According to Janin,-- a 7-foot dredge with a table area of 2,800 square feet uses about 1,000 pounds on the sluices and in the traps. Probably in common practice the range is to i pound per square foot of sluice area.

The sluice should be run long enough to plug all leaks before the mercury is added. Usually only the upper 2 or 3 boxes or a quarter or half of the sluice at most is charged with mercury, as otherwise consider- able loss occurs. During a run more mercury is added periodically.

'Bowie, A. J., op. cit., p. 244.

Wil.son. E. B., Hydraulic and placer mining, 3d ed., p. 230, John ".VUey & Sons,

Bowie. A. J., op. cit., p. 244.

"Janin. Charles, Gold dredging in the United States: U. S. Bur. Mines Bull. 127, p. 143. 1918.

SOC. I] lIYl)KAri,I( MINIXG 131

AVhenever the sluice is run down enoufjh to expose the riffles the mercury can be examined. If it does not show here and there with clean surfaces nearly to the top of the riffles, more is added. As the quicksilver takes up gold near the head of the sluice it becomes pasty and finally quite hard and more should be added to keep it in a fluid condition.

The use of mercury in recovering gold from sluice-box concentrates is discussed in the following section.

Amalgamating plates should be u.sed only in treating fine material, generally well under one fourth inch in size and preferably not coarser than lO-mesh, as larger particles abrade the plates too rapidly and pre- vent building up of the amalgam. Consequently, the application of plates to placer mining is limited to the stamp milling of some drift-mine gravels and the treating of fine undere-urrent or other screened sands. The use of plates in stamp milling is a phase of metallurgy beyond the scope of this paper, and reference is made to any standard text or hand- book on gold milling.

None of the other applications of amalgam plates to placer raining is of particular importance, probably because the recoveries seldom have justified the labor and expense. Plates may be set in undercurrents treating finely screened sands, such as beach sands or the Snake River gold-bearing sands. They usually are covered with burlap to assist in retaining the gold until it has come in contact with the amalgam. Many other amalgamating devices have been applied to such material, but none is known to the authors to have been of greater value than properly designed sluices and riffles.

Separation of Gold and Platinum-Group Metals From Concentrates General

No sluice box or other type of gold saver used in large-scale placer mining makes a clean separation of the valuable minerals. The concen- trate obtained must be treated further to make a marketable product. Concentrate obtained in cleaning bedrock in some types of mining is treated similarly to sluice-box concentrates.

The concentrate may be cleaned by panning or rocking in auxiliary sluices or by blowing, or it may be amalgamated in a special type of appa- ratus. The treatment will depend mainly upon the scale of operations, the proportion of black sand in the concentrate, and the characteristics of the gold. The general methods of cleaning concentrate with pans, rockers, or small sluices are the same as those in small-scale mining, described in a previous paper,- except that more care is required and smaller quantities are treated at one time. In treating small quantities of concentrate, however, it should be remembered that colors of gold so fine as to present great difficulty in their separation by panning or rock- ing are probably of small value, and their loss would be inconsequential.

If precise results are desired for sampling or testing, the concen- trates should be amalgamated.

23 See also Chapman, T. G., Treating gold ores: Arizona Bur. Mines Bull. 133, Univ. Arizona, 1932 ; a brief, nontechnical description of the methods of treating gold ores.

Gardner E. D., and Johnson, C. H., Placer mining in the western United States, general, hand-mining, and ground-sluicing : U. S. Bur. Mines Inf. Circ. 6786, pt. 1, 73 pp., 1934.

132 PLACF.R MINING FOR OOLD IK CALIFORNIA [Bull.135

Panning

Panninf? is the simplest method of separating the valuable constitu- ents from the worthless material and generally is used in small-scale operation. The method, however, is tedious if the gold is very fine and the concentrate contains much black sand. Mercury may then be used in the pan to collect the gold.

Rocking

Larger quantities of concentrate may be treated in a rocker and the resulting .semifinal product cleaned further in a pan. A final or almost final product, however, can be made in a rocker, the flat, smooth bottom of which, set on a gentle grade with screen and canvas baffle removed, offers an ideal surface for the purpose.

The concentrates are placed at the upper end, and a small stream of water is poured over the .sand while the rocker is swayed gently back and forth. The lighter material is washed down to the riffle at the lower end, and the coarser particles of gold are left behind. These are picked up with a scraper, and the operation is repeated, a portion of the concen- trates presently being discarded with each washing until at length all gold of appreciable value has been recovered. This method is satisfac- tory with ordinary concentrates, but if the gold is very fine, flaky, or par- ticularly light, porous, or angular, the .separation is tedious and unsatis- factory, and amalgamation is to be preferred.

The same general method may be used in the mine sluice to recover the bulk of the gold amalgam.

Auxiliary Sluices

Sometimes an auxiliary sluice is used to reduce the volume of con- centrate from the mine sluice or to treat concentrate after it is amalga- mated. The small sluice in turn must be cleaned up. At one mine a 12-inch box was set up in the main sluice into which was shoveled the riffle concentrate from below.

Blowing

The grains of sand remaining in an almost final product may be removed from the gold by blowing. A flat metal or paper sheet, such aa a piece of drawing paper or a large flat tin about 2 feet square with the edges bent up about one-half inch, is best for the purpose. However, with care ami skill the operation can be performed in a common gold pan, as is done by many prospectors, particularly when cleaning dry-washer concentrates. The material should be perfectly dry. Much effort is saved by using a magnet to take out any magnetite sand in the concen- trates; often this mineral comprises as much as 90 percent of the mate- rial. A piece of paper folded around or held against the end of the mag- net will keep the magnetite from sticking to the metal. When all the magnetite is removed, blowing gently on the remaining sand and gold will drive the former to the farther edge of the sheet, leaving the gold behind. In mo.st instances the loss of a few fine colors is not serious.

Analgamation

In Ordinary GoUt Pans. A small (pumtity of quicksilver, ranging from an ounce to a quarter of a teaspoonful, will catch all the gold from a pan of sluice concentrates. The mercury is simply placed in the pan with about T) pounds of concentrates and agitated under water until no

Sec. I] HYDRAULIC MINING 133

more free gold can be observed. Then the sands are panned off, care being taken not to lose any of the amalgam or fine drops of mercury, which gradually will run together into a single mass. If the concentrates are nearly all black sand only a small quantity should be washed at a time, but if much light sand or rock is present larger (}uantities can be washed. Copper-plated pans or pans with steel rims and copper bottoms are available and are useful for saving fine gold in concentrates. The copper is coated with mercury by first cleaning it with emery paper, then rub- bing clean, bright mercury or amalgam on it until it presents a smooth, shiny surface. The gold in the material being treated is picked up quickly by the amalgam surface. Only fine sand can be treated to advan- tage as coarse sand or gravel will scour the amalgam off the copper. As fast as amalgam accumulates on the copper it is scraped off with a smooth, dull-edged iron scraper such as a putty knife. More mercury may then be added to keep the surface bright and in a "receptive" condition.

Amalgamators. In nearly all large-scale operations most of the gold is amalgamated in the sluice boxes or on the riffle tables, and the amalgam is separated from the sands during clean-up operations or from the con- centrates by rocking or panning. Tarnished or rusty gold or very fine gold, however, does not amalgamate readily because it is difficult to make contact between the gold and quicksilver. Such gold, generally included in a black-sand concentrate, requires agitation in the presence of quick- siWer or, if rusty, grinding to remove the interfering coat for satisfactory amalgamation.

Mechanical amalgamators are used to treat such materials. Occa- sionally all of the concentrate from the sluice will be treated in an amal- gamator, particularly if it contains rusty gold. The charges for the amalgamator should be kept clean ; grease especially interferes with amal- gamation.

A common type of amalgamator is the clean-up pan, which consists of a cast-iron, cylindrical, flat-bottomed barrel or tub 1 or 2 feet in diam- eter for small-scale work and 4 to 6 feet in diameter for mill service. The concentrate with 1 or 2 percent quicksilver by weight is placed in the pan with suiflcient water to make the mass fluid and agitated by a revolving spider. The quantity of water added should be sufficient only to permit agitation without too great strain on the machine. The pulp should be thick enough to hold particles of mercury in suspension. Shoes on the lower end of the spider arms slide on a flat, circular race in the bottom of the barrel, thus adding some grinding to the agitation. After running for 1 or 2 hours the batch may be emptied through a drain plug in the bottom of the barrel and the mercury and amalgam separated from the sand by panning. Some pans are provided with side drain plugs at vari- ous elevations. The rotation may then be slowed from its usual speed of about 60 r.p.m., the shoes raised enough to stop the grinding, and water added. This will settle the quicksilver and amalgam ; the waste sludge can then be flushed out through the upper drain plugs and almost com- plete cleaning of the amalgam and mercury made in the pan itself.

Another device, the so-called amalgam barrel, generally is used at large stamp mills and occasionally is employed in placer operations, par- ticularly in dredging, to treat accumulated black sands, scrap metal, and other possible gold-bearing material from clean-up operations. It is merely a cast-iron or steel drum revolving on a horizontal axis like a ball

134 I'LACER .MININfi FOR (iOLD IN CALIFORNIA [Bull.135

mill and fittetl with suitable drain plugs, handholes, inanlioles, or remov- able ends, depending on its size and use. The material to be treated is l)iaoed in the barnl with quicksilver, water, and a few iron balls, and the barrel is turned slowly for an hour or several hours. The barrel may then be flushed with water from a ho.se to wash away the lighter products of grinding, turiu'd ovei'. and emptied into a tub, the amalgam and mer- cury being recovered by jianning. Potassium cyanide .sometimes is added to brighten the gohl ; oidy enough is used to make a very weak solution.

An amalgamator that occasionally is used, especially if a part of the gold is attached to particles of (piartz, is the Herdan pan, which is rela- tively simple in construction and cheap to operate. The pan consists of a revolving cast-iron bowl, usually .'5 to 5 feet in diameter, with a raised central hub for the drive shaft, giving it the form of a circular trough. The bowl is supported either by the drive shaft or by rollers and is set with a tilt of about 20 or from the horizontal. It is driven at 10 to iO r.p.m. cither by a crown gear on the inclined shaft of the bowl or by a ring gear on the bottom of the bowl. One or two large cast-iron balls roll in the trough as the bowl revolves. Quicksilver is placed in the bowl with the charge, and as the device revolves a stream of water is directed into it and overflows at the lowest point of the rim. The material to be amal- gamated may be added in batches or, if it is to be ground as well as amal- gamated, by an automatic feeder, the slimes and fine material overflowing to waste; the bowl then acts as a classifier. For placer concentrates the batch process is used, 100 pounds or more being treated at a time. Too large a quantity of .sand lessens the grinding effect of the balls.

A 1- or 2-cu.ft. hand- or power-driven concrete mixer is a convenient amalgamating device for the small- to medium-scale placer miner, par- ticularly if part of the gold is rusty. It co.sts only $20 to $30, excluding the small gasoline engine, and can be obtained from hardware stores or mail-order houses. The charge for such a machine is two or three pails of concentrates, 1 or 2 pounds of quicksilver, a few round cobblestones 3 or 4 inches in diameter, and water. About a 1-hour treatment will amalgamate practically all of the gold. The charge is emptied into a settling tub and then washed in a pan or small sluice box to recover the amalgam and mercury.

Regardless of the amalgamator used, too violent agitation of the mer- cury must be avoided, otherwise excessive flouring hinders amalgamation and makes it difficult or impossible to recover the quicksilver.

Cleaning A maUjam. The mixture of quicksilver and amalgam from sluice-box clean-ups u.sually contains much more mercury than amalgam. It can be freed from sand, scraps of iron, and other .solid impurities by careful panning and by washing with a jet of clean water. The amalgam can then be .separated from the quicksilver by straining the mixture through buckskin, chamois skin, close-woven canvas, or other .strong, tight cloth. This generally is done by hand, preferably under water to pre- vent scattering of the mercury. The quicksilver tlius filtered off contains at the most only about one-tenth percent of gold; this mercury is desir- able for recharging the boxes as the .small amount of gold makes it more active. The amalgam, after squeezing, still contains some mercury, part of which may drain off if the mass is suspended for several hours in a funnel or other similar container. With or without this last refinement, which one dredge operator used with success, the stiff, pasty amalgam is

Soc. T] HYDRAUIilC MIMN'G 135

now ready for fire treatment to separate the gold. It eontaiiis 25 to 55 percent, eoninionly about a tliird by weiprlit of {?old and silver.

Extracting Gold From Amalgam Heating

Altli()U<rh i-etortinp: is tlie comiiion inetluul of separatinpr the gold from the (|uicksilvei- in amalfram at dredf'cs and other larpre-scale opera- tions, the merenry in small <|uaiitities of amal<:<im may be volatilized by simple heatinjr. A common method is to heat the amalgam on a clean iron surface over an open fire or for<re, or in a furnace, until all the mer- cury is driven off. This is the usual expedient of the single miner or small operator who does not object to the loss of the small quantity of ([uicksilver involved. The mcrcui-y vapor may appear as heavy white fumes. Whether visible oi- not, mercury vapor is exceedingly poisonous, and the work must not be done except where a draft can be depended on to carry all the vajior away from the operator. As stated elsewhere, mer- cury boils at 675" F., a temperature about halfway betAveen the boiling point of water and the first visible red heat of iron. However, it volatil- izes at the boiling point of water enough to be dangerous to the health of persons exposed to it. Conse(|uently, it should be handled carefully, particularly to avoid iidialing its vapors.

In another method of recovering the gold from small amounts of amalgam, a potato is used as a condenser. This is a device popular with prospectors because it is very simple, yet saves part of the mercury that would be lost by the method previously described. A large potato is cut smoothly in half, and in the flat surface of one-half a recess is hollowed which .should be considerably larger than the amount of amalgam to be treated. The amalgam is placed on a clean sheet-iron surface, the half potato is placed over it, and the whole is set over a hot fire. For conven- ience it may be done in a frying pan or the scrap of sheet iron put on a flat shovel so that it can be withdrawn readily from the fire. Some mer- cury vapor will escape under the edges of the potato, and, as before, these fumes must be avoided. After 15 or 20 minutes of strong heating the potato may be lifted oflP for inspection. If all the mercury is gone from the gold the potato may be crushed and panned, and a considerable part of the mercury will be recovered. It may be desirable to heat the gold further to ainieal it ; this can be done without removing it from the iron plate. Any tinned or galvanized metal intended for use in this process should be heated redhot and then scoured to remove all traces of the coat- ing so that a clean iron surface will be presented.

A laboratory method of separating the gold is to put the amalgam in a small beaker and di.ssolve the mercury in a 1 to 1 solution of nitric acid and water. When all the mercui-y is dissolved, the gold may remain as a sponge, which can be washed gently in water and annealed in a small porcelain crucible. More frequently the gold Avill be recovered as a fine dust, which also can be washed and annealed but is less easy to handle.

Retorting

A very small amount of amalgam can be retorted quickly and easily in a laboratory in a gla.ss tube 18 to 24 inches long, sealed at one end and bent 2 or 3 inches from that end to a slightly acute angle. A large tube three-fourths inch in diameter is best. The amalgam is broken into pieces small enough to be dropped into the closed end where it is then

136 PLACER MININfi FOR GOLD IN CALIFORNIA [Bull. 135

heated, tlie fumes condensing in the long open end of the tube. The gold can be annealed by heating the tube to redness after all mercury is driven off.

A retort for treating a few ounces at a time can be made cheaply of ij-inc'h pipe, pipe connections, and a large grease cup. The lower and open end of the ij-inch pipe is inclo-sed in a larger pipe. Cooling water i.s poured through the space between the two pipes from an open connec- tion in the top of the outer one. The charge of amalgam is i)laced in the grease cup cover which is then screwed into place; graphite lubricant is placed on the threads to make a tight joint. Heat is applied to the grease cup, and the (piicksilver is condensed in the lower end of the pipe. The method of using and the general arrangement of the device are similar to those of tlie next retort described.

The typical (piicksilver retort for placer mines is a cast-iron pot with a tight-fitting cover in which a hole is tapped to accommodate the con- denser pipe. The capacities of such retorts range from a few to 200 pounds of amalgam, or about a quarter pint to 2 gallons. They are listed in chemical-supply catalogs at prices ranging from $4 to $30, not includ- ing the condensers. The condenser commonly used with this type of retort is an iron pipe 3 or 4 feet long leading from the hole in the retort cover at a downward angle of 20 to 30" ; it is encased for most of its length in a considerably larger pipe through which cooling water is circulated. When heat is applied to the charged retort the mercury vapor enters the condenser pipe where it cools and condenses; it trickles down the pipe into a ves.sel placed under the open end of the pipe. In the treatment of a large amount of amalgam the temperature of the pipe might be raised to a point where some of the vapor would escape; therefore, a cooling device is necessary.

The retort may be heated over a large bunsen burner, by a gasoline blow torch, in a forge, or in one of several types of furnaces built for the purpo.se. Very high temperatures are unnecessary, and a wood fire is considered better than a coal fire. The flame should cover as much of the retort as possible.

A rigid, .strong .stand for the retort and condenser should be con- structed if the apparatus is to be used regularly.

The retort should be coated on the inside with chalk, or painted with a thin pa.ste of chalk, clay, mill slimes, or a mixture of fire clay and graph- ite and thoroughly dried before putting in the charge. This prevents the gold from sticking to the iron, which sometimes causes trouble. A lining of paper .serves the same purpose but tends to form an objec- tionable deposit in the condenser pipe.

The retort should not be filled over two-thirds full of amalgam (a third or half full when retorting liquid mercury), otherwise there is dan- ger of .some of the contents boiling over into the condenser tube. The amalgam is broken into pieces and piled loosely. Then the cover is put on and clamped tightly with the wedge or thumbscrew provided, first making sure that the attached condenser pipe is clean and free of obstruc- tions. The ground joint between the cover and body of the retort is seldom tight enough to prevent leakage and should be luted with clay or some .sealing compound. One satisfactory cement is made readily by moistening a mixture of ground asbestos and litharge with glycerin.

A low heat is applied at first, then after 10 or 15 minutes the tempera- ture is increased just enough to start the mercury vaporizing and con-

Sec. I] HYDRAULIC MINING 137

densingr. Too rapid heating harms tlie retort, and only enough heat should be used to maintain a steady trickle of quicksilver from the con- denser. When no more mercury appears the temperature should be increased for a few miiiutes to red heat to drive the last of the quicksilver out of the retort ; then the fire should be withdrawn from the retort and the latter allowed to cool. Some mercury vapor always remains in the retort, and the operator should take care not to breathe these fumes upon taking off the cover.

The likelihood of dangerous amounts of mercury vapor passing through a long cold pipe without condensing is very small. However, if much amalgam is to be retorted, or if the operation is of daily or fre- quent occurrence, it usually is desirable to provide some form of water seal at the end of the condenser tube to prevent the escape of such fumes. Many miners have followed the dangerous practice of submerging the end of the condenser pipe in the bucket of water used to receive the con- densed mercury. This should not be done, as a slight cooling of the retort would cause water to be sucked into the pipe, and if the water reached the retort an explosion would follow. Such an experience has taught more than one "oldtimer" the danger of this practice.

If the volume of the receptacle is very small compared with that of the condenser pipe and if the discharge pipe is barely submerged the danger is avoided, as any large rise of water in the pipe would lower the water surface enough to break the suction. At some properties the end of the condenser pipe is in a large sheet-iron cylinder, a few inches in diameter, open at the lower end, which may be placed 2 or 3 inches into the water in a receptacle of only slightly larger diameter, thus making a good water seal yet avoiding the danger of explosions.

The simplest method is that recommended by Louis ;2" it consists merely of tying a piece of cloth such as canvas or burlap around the end of the condenser pipe and letting it dip in the water 2 or 3 inches below, forming a damp filter which will condense any escaping vapor yet not be tight enough to permit water to be sucked into the retort.

Large gold mines use cj'lindrical retorts, usually set horizontally in specially built furnaces. Such installations probably would be needed in placer mining only by large dredging companies. The operation is similar to that of a pot retort, except that the amalgam usually is placed in several small iron trays, rather than on the floor of the retort proper, and charged through a door or removable cover at one end of the retort, while the condenser is attached at the opposite end.

Separation of Platinum-Group Metals From Gold

In several localities in the AVestern States sluice concentrates from placer mining are likely to contain platinum or its associated metals in sufficient quantities to be of economic interest. The .separation of these minerals from gold is difficult. Their specific gravity is too near that of gold to permit a separation by panning. Coarse platinum particles can be picked out of the gold by hand, but most placer platinum is exceed- ingly fine. Although platinum does not amalgamate, quicksilver can be made to coat and hold platinum particles by treatment with chemicals; thus it is possible to sepai-ate successively the gold and platinum from the concentrates.

Louis, Henry, A handbook of gold milling, p. 38C, London, 1894.

i:i{ minim; ion cold in cArji-oKNiA

[liiill. l;];

See. T] iiYDRATirjc minino 139

One dredging company in California wliich recovers platinum metals uses the following clean-up procedure :-"

In cleaning up, the riffles arc removed from the sluices, starting at the head end, carefully washing them off and washing the sluice down with water from a hose. This washes away the light sands and concen- trates the amalgam and heavy sands, which are carefully scooped up into buckets and carried to a "long tom" for further treatment. In the long tom most of the mercury and amalgam and some of the platinum-group metals are caught in the upper box. Most" of the platinum, some rusty gold, scattered particles of mercury and amalgam, and the sand and ref- use are washed out over riffles where the heavier components are caught. The sand finally passes through a screen at the end of the tom, into a sand box, and the gravel goes to waste. The mercury and amalgam from the upper box are transferred to a bucket, in which the gold amalgam settles to the bottom ; the lead or other base-metal amalgams float on top. The latter is partially cleaned by panning, Avhich separates some metallic platinum, then retorted. The gold amalgam is squeezed free of mercury and likewise retorted.

The gold amalgam, usually containing about 55 percent gold and silver, is retorted in a standard make of gasoline-fired retort. The mer- cury condenses in a w-ater-jacketed pipe and drains into a bucket of water. The gold remaining in the retort is transferred to a crucible and fused in the same furnace. It is then poured into molds, producing bars which are shipped to the Selby smelter. The bullion averages 890 parts gold, 90 parts silver, and 20 parts impurities per 1,000.

The riffle concentrates and sand from the end of the long tom are placed in small batches in a steel barrel mill 4 feet long and feet in diameter. Mercury is added and the batch ground for 1 or 2 hours. Then the amalgam is removed by panning and added to the other base amalgam for retorting. Further panning and rocking reduce the remain- ing sand and concentrates to a product containing about half black sand and half platinum, by volume. This is treated by the addition of water, mercury, zinc shavings, and sulphuric acid ; this causes the platinum metals to be coated and held by the mercury, so that a final separation from the sand is possible. The final concentrate is then washed with water and drained to remove acid and excess mercury, after which treat- ment with nitric acid dissolves the mercury, leaving a final residue of platinum, iridium, and osmium.

The base amalgam, which includes shot, bullets, and small particles of copper and brass scrap, as well as some precious metals, is retorted to recover the mercury, melted, and poured into molds to form bars for shipment to the smelter. These bars range in value from $1 to $8 per troy ounce.

The United States Mint does not now buy platinum or pay for the platinum content of gold shipments. The following buyers of crude platinum reported purchases in 1930

American Platinum Works, 22") New Jersey Railroad Avenue, Newark, N. J. Baker & Co., Inc., 54 Austin Street. Newark, N. J. J. Bishop & Co. Platinum Works, Malvern, Pa. Sigmund Cohn, 44 Gold Street, New York, N. Y.

Patman, C. G., Method and costs of dredging auriferous gravels at Lancha Plana, Amador County. Calif.: U. S. Bur. Mines Inf. Circ. 6659, pp. 12-13, 1932.

Davis, H. W., Platinum and allied metals in 1930 : Mineral Resources U. S., 1930, pt. 1, p. 105, 1931.

140 PLACKK MINING TOU GOLD IN CALIFORNIA [Bull. 135

Thonins J. Doo & Co., 1010 I.iIIcis Ruil<lin', Chicago. 111.

Kiistonliul.or & Ldirf.-hl. L'4 John Sln-ot, York, N. Y.

rarific riatiiMiiii Works, Inc.. S14 Sondi S|irin>; Street, I,os AiikHcs, C-iIif.

Schwittcr. CIomt & Slaitw r:ith<T. Inc., .".lli r.iss.iic Avenno, X.nvark, N. J.

Wildberg llros. Smell in;; & Helinin- Co., 741! .Market Street, San Francisco, Calif.

Lots ranging; from less tlian an ounce to hinidreds of ounces ordinarily are marketable but preferably not less than 2 ounces. .Settlement is based on assay, either by the buyer or, for larjie lots, by both parties. The price paid in 1!)30 for domestic crude platinum ranjcd from $30 to $40 per troy ounce the average quotation for the refined metal was $45.

Melting Gold

The spongy mass of gold left after retorting can be sold to the mint or other agencies just as it comes from the retort, but generally it is melted and poured into molds to form bars or ingots for marketing.

The melting generally is done in graphite crucibles placed in a special furnace. In small operations the crucible is usually heated in a blacksmith forge in which coke is used for fuel. The graphite crucible must be dried thoroughly before it is used by being warmed gradually for several hours.

Small quantities of gold frequently are melted without fluxes in make-shift devices such as dented frying pans ; in most instances, how- ever, .some flux is desirable. If the gold is fairly pure, that is, has a bright yellow color, it may be melted with only a small quantity of borax glass for flux. If, however, it contains impurities and is grey or black in color, the melt requires larger quantities of flux to take up these impurities. Sometimes niter, sodium carboiuite. or silica is used to remove specific impurities. The flux is melted first, then the gold is placed in the crucible and likewise melted. Enough flux is used to form a covering about one half inch deep over the molten metal.

In large-scale operations the melted gold is poured from the crucible into cast-iron molds holding 50 to 1. 000 ounces. A mold should be larger at the top than at the bottom so that the bullion will drop out readily when it is inverted. A mold 3 inches by 12 inches at the top, 1 inch narrower and shorter at the bottom, and 3 inches deep holds about 1,000 ounces. The common practice is to smoke the mold over an oil flame, then to heat it before pouring the gold. Another practice is to coat the mold with graphite or oil or to pour a (juarter inch of vegetable oil in the mold and heat it to boiling, then to i)our the gold into the oil.

When the gold has just set in the mold and before the slag has hard- ened, the contents of the mold are tipped into water. This granulates most of the slag, aiul any particles still adhering to the gold usually can be bni.shed off. Tightly adhering slag can be loo.sened by washing the gold with nitric acid.

The bar of bullion may be stamped with identifying marks or names, or these may be cast in reverse in the bottom of the mold. The bar is then ready for market.

Sampling and Weighing Gold Sampling

There are several methods of sampling gold bullion. The most accu- rate one is to dip a sample from the melted bullion before casting it.

"Davis, H. W., op. cit., p. 105. ... "'"f /'M Reserve Act of jyji. a Iicen.se from a U. S. Mint is required for melting gold. A copy of this act i.s available from Superintendent of Documents, (Jov- ernment Printing Office, Washington, D. C, for 10 cents.

Sec. I] TivnHATTLic MiNixn 141

A {graphite rod suitably shaped at one end to dip up the desired amount of gold, usually 1 to 5 f>rams, is heated redhot, stirred about in the melt, and lifted out with the sample. The sample is then poured into an oiled mold or into a .shallow bath of heated oil. This method has been used by a few mining companies and is said to eliminate slight inaciniracies to which other methods are subject. It is impracticable for small amounts of gold and is inconvenient in that the sample is not obtained in a form convenient for assay; except for bullion containing large (piantities of base metals, simpler methods generally are sufificiently accurate.

Other methods depend on taking samples from the solid cast bar of bullion, (.'hips can be cut with a cold chisel from the surface of the bar, at one or more places, hammered thin, and trimmed to the desired weight for assay, or holes can be drilled aiul the drill cuttings used for samples. The latter method is used most. Holes an eighth inch or less in diameter are drilled a quarter to a half inch into the bar, usually one on top and one on the bottom of the bar, on the center line a short distance from the opposite ends. Two diagonally opposite corners, one on top and one on the bottom, are sometimes preferred, although the difference probably is negligible. It has been found that in bullion containing base metals there is a strong tendency for the base elements to segregate at the bottom of the bar and for the top surface to be above the average fineness. Special methods of sampling then must be used. However, for most placer-mine bullion a sample of the desired weight, obtained in almost any convenient fashion, will be sufficiently accurate. Drill samples taken as described above usually check the mint or smelter return within 5 parts per thou- sand.

When gold is to be shipped to the mint, assaying the bullion is a needless expense as there is no recourse from the mint assay returns.

Weighing

Analytical balances suitable for weighing small amounts of gold with great accuracy" cost from $150 to $300, and balances that will weigh large amounts of gold, such as the gold bars shipped to the mint by mining com- panies, with sufficient accuracy so that their value can be calculated to the nearest cent, are very costly. Balances capable of weighing a few ounces of gold to the nearest cent can be purchased for $20 to $30, and convenient pocket scales, either of the hand-balance type or arranged to be set up on the cover of their cases as mounted balances and capable of weighing 3 or 4 ounces to the nearest cent, are sold by most chemical- supply houses at prices ranging from $2.50 to $15, including weights. With little or no expenditure a set of hand balances can be made, which will weigh 1 or 2 ounces of gold to within a grain or the nearest 5 cents. The balance beam may be of wood, 6 or 8 inches long, suspended by a pin, needle, or bent wire hook through a hole in the exact middle of the beam. The pans can be made of tin, cut to 2 inches in diameter and hammered dish-shaped, or of the lids of small tin cans, each suspended by three threads from the ends of the beam by means of bent wire hooks. No pointer is necessary, as the beam can be leveled closely enough by eye. It is not necessary that all parts be of exact weight, as the balance beam or the pans can be trimmed to make the assembly balance. For even approximate accuracy, however, it is necessary that the pans be sus- pended from points on the beam the same distance from the center bear- ing, and for stability the end bearings must be slightly lower than the

142 I'I,A(i:k MisiNf; iok (ioi.d in rAMFOKNiv fllull.l'jr)

center one. The nicer tlie const ruction and the more nearly frictionless the method of .suspension, the jjreater tlie accuracy; hut even with very little attention to these points a sensitivity of less than a jrrain is obtain- able when wei:hinjr as much as 2 ounces. Weijrhts can be purchased in convenient sets for ;")() cents or more or can be made or improvised from bits of wire or sheet metal cut to match any available standards.

Marketing Placer Gold

Five classes of buyers usually are available to the miner who wishes to sell }?old dust, retort spon-'e, or bullion bar: (1) Individual gold buj'ers; (2) local stores; local banks; (4) smelting companies; and (5) United States mints and assay offices. If the miner has base bidlion or conceiitrates the smelter or custom mills are usually his only market.

Local stores are the principal buyers of snudl amounts of gold, rang- ing in value from a few cents to $r)U or more. The merchant, who is often tlie chief retailer of supplies to the miners, finds it brings him trade to act as a connni.ssion buyer of gold, making it possible for the prospector and miner to convert their winnings promptly into cash. If his commission is fair, this is satisfactory, as it saves the miner much distasteful annoy- ance in preparing his gold for shipment, filling out various registration and report forms, and then waiting several days for his check. It like- wise makes possible the sale of less than 1 ounce of fine gold at a time, which is the least amount of retort sponge, gold dust, or nuggets the mint will accept. The discount of the merchant ranges from $1 to $2 per fine ounce. The miner must remember that no placer gold is pure and that the merchant has only his judgment to tell him how much the mint will pay for his gold. Not all gold from a district assays the same degree of fineness, and the merchaint is not to be blamed for staying on the safe side.

In most mining districts there are assayers, company officials, jewel- ers, metal brokers, or other individuals who for profit or for the conven- ience of employees, lessees, or customers make a practice of buying gold in small lots from prospectors and miners and paying cash for the value of the estimated weight of fine gold, less certain charges. Likewise banks in many districts receive gold, either purchasing it outright on the basis of their own or commercial assayers' anal,yses, or merely acting as ship- ping agents, receiving the gold, shipping it to the mint, and paying the miner upon receipt of mint returns. In the latter case a connni.ssion of about 1 percent usually is charged, for which the bank assumes all risk and trouble otherwise taken by the miner himself.

A few smelters or refineries buy gold or silver metals; the melting and refining charges probably will closely approximate those of the mint. Most smelter or refineries handling precious metal ores buy gold-bearing concentrate. Smelting charges on such material are variable, and an inquiry, accompanied by a close description or a sample of the material offered for sale, should be made in advance.

(Jold can be shipped by express or by mail. If by express, the parcel can be insured with the express company for its full estimated value. United States mail shipments usually are sent as registered first-class mail and should be insured. The mail registry .system provides insur- ance in graduated amounts from $5 to $1,000 at a cost of 15 cents to $1, including the registration fee but excluding po.stage. If regular mail shipments of considerable value are being made, it is possible to secure commercial insurance for them. However, for amounts greater than a

Sec. I] iivnuAur-ic MINING 143

few oiniees the first-class postajxe rate of 3 cents per ounce becomes so costly that express shipments are advisable. All shipments must be pre- paid.

The best container for shippin*,' ffold, either by mail or express, is a lead-sealed canvas sack, securely tagjed with the addresses of the sender and addressee. Gold bars may be wrai)ped securely in canvas and packed in wooden boxes.

When a shipment of gold is sent to the TTnited States Mint a letter should be sent sepaVately containing the. prescribed affidavits. Form TG-in, for a person shipping gold that he has mined himself, and form TG-21, for gold buyers, can be obtained by writing to a United States mint or assay office. Form TG-lf) need not be sworn to if the amount of gold is 5 ounces or le.ss. Since January lO.'U the mints have paid $35 per troy ounce of fine gold, less one-fourth of 1 i)ercent, as compared with the former price of $20.67-}- per ounce.

"The mint charges $1 for meltiiig any deposit of 1,000 ounces or less and 10 cents additional for each 100 ounces over this amount. An extra charge of $1 or more is made for melting gold dust or gold containing non-metallics if the loss of weight in melting is more than 25 percent.

If the gold is 992 fine, or finer, no charge is made for parting and refining. If less fine, or if more than 50 parts base metals are present per 1,000, charges of 1 cent to 5 cents or more per ounce are imposed for parting and refining. Bullion less than 200 fine is not accepted.

Current market prices are paid for the full silver content ; however, if necessary forms are submitted for silver qualified under Executive Proclamation of December 21, 1933 the depositor will receive the number of silver dollars that can be coined from one half of the fine silver content. No other constituent in the bullion is paid for.

Laws Regulating Ore Buyers California laws reciuire ore buyers to take out licenses. The Cali- fornia Ore Buyer's License Act, passed in 1925, includes as buyers all persons sampling, treating, or buying gold dust, gold or silver bullion, gold or silver specimens or ores, or concentrates of these metals and gives the Staje Mineralogist the duty of licensing such persons.* The license fee is set at $15 per year if the gold and silver treated or purchased in a year exceed $1,000 in value oi- at $2 if less. The licensee is required to keep on record the names of the sellers, the amount and description of each lot purchased, the stated source of each lot, and other data and to report all purchases monthly to the State ]\Iineralogist. Provision is made for the issuance of licenses, recovery of stolen metals, and penalties for violation of tUe act. The latter are severe. No regulation, of course, is placed upon the gold buyer as to terms of j)urchase, nor is this a matter of record under the act; however, one effect of the act, which primarily is intended to prevent the ready sale of stolen gold oi- silver, doubtless is to improve the chances of the small producer getting fair treatment from ore buyers b\' driving dishonest dealers out of business.

>Rickett.s, A. H., American mining law: Calif.. inia |iiv. Mitu-s Hull. IL':!, pp. (JOI)- 664. 1943.

144 PLACER MINING FOU GOLD IN CALIFORNIA [Bull. 135

Debris Dams

When Indraulic mining was at its heipht, annual production of gold by that method reached $1 ;"),()()(),()()(), and averaged $1(),()00,()00 per year for the 30 years ending in 1884. Tlie best estimates- of the amount of gravel that was mined to recover this gold indicate that 1,205,000,000 cubic yards was washed into tributaries of the Sacramento alone. This is equivalent to a body of gravel 10 miles long by 1 mile wide by 125 feet deep.

' ' The immense scale of these operations caused serious silting of the river channels and partial blockage of streams tributary to them, so that in flood times much damage was done to farm lands adjacent to the rivers.. In conse(|uence there were many actions at law in the State courts, which resul-ted in injunctions against the mines. Immediately prior to the general closing of hydraulic mining the annual yield is estimated to have been reduced to $5,300,000.3

Finally the decree of Judge Sawyer of the United States Circuit Court restrained the North Bloomfield Mining Company from discharg- ing debris into the streams. Tliis was in 1884. The court reserved the power to modify or suspend the injunction upon the defendant's showing that conditions had been so changed that the discharge of debris might be conducted so as not to continue the nuLsance complained of. That is to say, hydi-aulic mining was not declared to be illegal, but the dis- charge of debris into the streams was forbidden. The provision of a dam to restrain the debris might make the necessary change in conditions to allow mining to be resumed.

Mine after mine was closed by injunction based upon this decision and the federal legislation pas.sed in 1893 (the California Debris Com- mi.ssion Act, or Caminetti Act) embodied the principles declared by these injunctions, but enacted moi-e severe penalties for their non-ob.servance. The Caminetti Act is printed in full in the appendix of this bulletin. It applies oidy to the territory drained by the Sacramento and San Joaquin iJivcrs.

Under the Caminetti Act, charges for debris storage behind dams contemplated by the law were set at 3 percent of the gross proceeds of a mine. As this was inadequate to amortize the cost of such dams, the Caminetti Act was in effect more than 40 years before any debris dams were built. An amendment approved June 19, 1934, set the charges on the basis of cubic yards of gravel mined behind the dam. The matter of building such dams by the Federal (Jovernment was reviewed by the California Debris Commission, and a report containing recommenda- tions against the building of debris dams was submitted to the Board of Engineers for Kivcrs and Harbors under date of February 13, 1935. A hearing in j)n) of this report was held before the Board of Kivers and Harbors in Washington on Ai)ril 15, 1935, and Walter W. Bradley, Cali- fornia State Mineralogi.st, presented before that board a brief to show the value of placer gravel that would be made available for mining behind

.larman, Arthur, An inve.stiRation of "the feiisil)ility of any plan or plan.' whprehy hydraulic niiiiiiiis' opiration.s can be resumed in thi.s .state" ; California State Min. Bur., MinlnK In California, State Mineralopi.st's Kept. 2.i, pp. .'".4-1 1(1, iy27.

3 LlndKreii, Waldeniar. The Tertiary gravels of the Sierra Nevada of California: U.S. C.eol. Survey Prof. Paper 73, p. :i], IHI 1.

'Haley, C. S., Gold placers of California: California State Min. Bur., Bull. 92,

Jackson, T. H.. Irvine, E. S. J., and Drinkwater, J. C, Report of the California Debris C'immis.sion : 74th Cong., l.st .m-.s.s., H. Doc. .50, pp. 9-34, 5 niap.s, llt.J.'i.

Sec. I] DEBRIS DAMS 145

such dams. Tliis brief was publislied in the July 1935 issue of the Cali- fornia Journal of Mines and Geology. A map shows locations of pro- posed dams.

The Board of Engineers for Rivers and Harbors'* under date of May 23, 1935, reported in favor of the construction of four dams at a cost of $6,945,000. The dams recommended were the Upper Narrows dam on the Yuba River about miles above its confluence with Deer Creek near Smartsville ; Dog Bar dam about 7 miles up the Bear River from the existing Combie dam or 3 miles southwest of Colfax; the North Fork dam on the North Fork Americaii River about 2 miles above its confluence with IMiddle Fork American River near Auburn ; and Lower Ruck-A-Chucky dam on Middle Fork American River a mile below the mouth of Canyon Creek.

An appropriation was provided by Congress, and two of these dams were built in the late thirties, and are now ready for use, the Upper Narrows dam and the North Fork dam. In an announcement dated January 5, 1942 the California Debris Commission established a tax rate of 3.11 cents per cubic yard for storage of hydraulic mining debris in the North Fork Reservoir on the North Fork of the American River, and a tentative tax rate of 2.30 cents per cubic yard for storage of debris in the Upper Narrows Reservoir on the Yuba River. Power is generated at the Upper Narrows, and this helps to pay for the dam, as provided in an amendment to the Caminetti Act approved June 25, 1938. This amendment is printed in the appendix.

Work was started on the Lower Ruck-A-Chucky dam, but the rock- formations at the proposed site were found unsuitable to support the dam, and the site was abandoned. If a dam is built to restrain debris on the Middle Fork of the American River, a new site farther up the stream will probably be selected. On the Bear River, where the Dog Bar dam was to be constructed, a conflict exists with regard to the genera- tion of power, and trouble has been caused by mud and silt in the water at the existing Combie dam. This conflict of interests makes plans uncer- tain for a debris dam on the Bear River. On the Yuba River, a mile beloAV the mouth of Willow Creek, near Camptonville, the Bullard Bar dam owned by the Pacific Gas and Electric Company has been available for storage of hydraulic mining debris for many years. The charge per cubic yard in 1941 was 2 cents.

Although the two debris dams mentioned above have been built and are ready for use, some serious problems still remain to be solved before hydraulic mining can be resumed on a large scale. One of these was brought out by case no. 60,474 in Department 4 of the Superior Court of Sacramento County, Carmichael Irrigation District and others vs. Lost Camp Mining Company and others. Carmichael Irrigation District alleged that damage was being caused by mud and silt from hydraulic mining above the North Fork dam on North Fork American River near Auburn. A temporary restraining order was issued in 1939 against hydraulic mining during the irrigation-season. This order allows hydraulic mines on North Fork American River to operate only between November 15 and April 30. McGeachin Placer Gold Mining Corporation

5 Bradley, Walter W., Dams for hydraulic debris : California Jour. Mines and Geology, vol 31, pp. 345-367, 1935.

Pillsbury, G. B., Control of mining debris on the Sacramento River and tribu- taries : 74th Cong., 1st sess., H. Doc. 50, pp. 3-8, 5 maps, 1935.

10—56968

140 i'(,.\( i;iv minim; ioi; (;iii.i) ( amiouma Uiill. i:!.')

jiiid Tlic .M;i\ flower (iravcl .Miiiiii;' ('oiiipjiiix- filed answers in this case ill .Maivh 1!M:; all('iii<; that the I'liited States ( ir>veniiii<'iit is a party in interest and that the ease sh(nld he translen-ed to a l'edoi-al court.

A second serious ))rohleni is oi" water-supply. IMauy of the ohl water-rij:lits. and even some of thc'-imclKs formerly used l)y hydraulic mines have heen ac(piired by power companies and irrijiati(ni districts. Where the old water ri<ihts are no lon<ier available, the only practicable metlnwl of replacing' them is by the stora<;e of surjdns water by means of larjic i-eser\<)ii's lii<:h in the monntains. This is, of course, expensive. Even wat er-rizlits have been retained by hydraulic minin;,' com- ]ianies. many of the ditches and tliinies refpiire rebuilding'.

])ecaiise of these difliciillies. consideration is bein' '/iveu by owners of larc jrold-l)earin- <ira\el deposits to meciianical methods of handling' <:ravel with tailing- storajc at the. mine as a substitute for hydraulic mining-. Such methods are rapidly bein;- reduced in cost, and may soon become available. ])redj:inji: may be used for some of the <lei)osits. but many of the larjie dei)osits are too deep for any dredge yet constructed.

Section

Geology Of Placer Deposits

New Technique Applicable To The Study Of Placers*

By OLAK 1'. JKNKINS

Outline Of Report

THKe

Introduction 1''

Object of the report 1-jl

Significance of improved exploration methods ]-j2

Aerial photography l'j3

Geophysical surveying l-jS

Physiography lij3

Study of desert processes

Stream sedimentation l'>3

Usefulness of contouring an ancient surface 1">4

Provinces of the ancient channels in California I'tH

Economic significance of the Tertiary gravels 1[)7

History of development 1">0

CLASSIFICx\.TION OF PLACERS 161

Outline of classification 161

General statement 162

Characteristics Of The Principal Types Of Placers 163

Residual placers 163

Eluvial placers 163

Stream placers 163

Glacial-stream placers 165

Bajada placers 166

Eolian placers 167

Beach placers 168

Preservation Of Placers 171

Modification Of Placer Deposits 171

Gold In Placers 173

Original source of gold 173

Release of gold from bedrock 174

Associated minerals 175

Transportation, deposition, and retention 178

Factors of concentration 181

Age Of Placers 183

Significance 183

Structural criteria 183

Paleontologic criteria 184

Physiographic criteria 185

Lithologic criteria 185

Coordination of criteria . 186

Life History And Habit Of Streams 186

Need for scientific background 186

Stream erosion 187

Preparation of material removed by erosion 188

Transportation 188

Deposition 191

Physiographic terms relating to streams 194

Desert processes 197

Need for establishment of working criteria 200

Geologic Conditions In The Gold Provinces Of California 200

Conclusion 206

Bibliography Of California Placers 208

Reprinted from April 19 35 California Journal of Mines and Geology, pp. 143-210. Chief Geologist, California State Division of Mines.

(149)

rLA(i;K MIMNC COIJ) IN CAI.I lOKN'IA

[null. 1:55

Fig. 46. Aeri the dredge at work Journal.

iKrapli of a dredseil .'trip along the Yuba Ri\( r ; u by Russell; reprinted from Engineering and Mt

Abstract Tho exploration of placers is a problem involving' nearly all i)hase.s of the seionce of >,'eolo{,'.v, especially physiography and streani sedimentation, neither of which has i>e<'n piven sufficient consideration in connection witli the economic problems concerned. The use of aerial photography is a great aid in the study of placers, both ancient and modern. The use of geophysics, when applied as a part of a geologic program of explo- ration, can materially assist in guiding drilling operations and underground prospect- ing, with the result that the cost of expensive development work can be greatly reduced and hastened to an earlier completion.

Placers arc classified according to the way they are formed : residual, eluvial, stream, glacial-stream, bajada, eolian. and beach. Since the ordinary stream placer is by far the most important, various phases of stream study are discus.sed in this paper. A need for further scientific study and the development of systematic working criteria is apparent.

The deideted placers of California consist largely of Recent and Pleistocene stream gravels and uncovered or buried, but easily accessible Tertiary channels, while the large reserves lie in more remote positions. These are exemplified by hidden buried bench gravels not connected with the surface nor with channels already worked, and by the lower untouched channels that lie on true bedrock beneath the 'false bedrock' of the dredged areas along the western foot of the Sierra Nevada. Some Pleistocene gravels still lie in pockets beneath the waters of the larger rivers where faults have caused down-dropping of the streani bed. Benches still lie in isolated regions such as the Klamath Mountains. The desert affords several types of deposits: stream placers buried by alluvial fans, reworked older placers, gravels interbedded with lavas, and the more recent bajada placers. !SIarine placers of Cretaceous, Eocene, Pleistocene, and Kecent periods exist in the state, which may in places be worth investigating.

The largest of all these possible reserves in California probably lies in the remain- ing buried Tertiary streani channels of the Sierra Nevada.

See. IIJ

(lEOLOCY OF PLACKK DKPOSITS- -JENKINS

Fig. 47. A mined-out segment cf the Tertiary Central Hill channel near Murphy, Calaveras County. Wliite rhvdlitic a.-<h, which covered this cliannel, is exposed on the left.

Introduction

Object of the Report

The gold-bearing gravel tlepo.sits or placers of California that still remain untouched lie, for the most part, in more obscure positions than the depleted gravels which formerly produced vast wealth for the state. The depleted gravels, which Avere once readily accessible but are now nearly mined out, fall into three principal classes:

Depleted placers

1. Keci'iit and Quaternary stream gravels.

2. Uncovered channels of Tertiary age.

3. Buried Tertiary channels, easily located.

About one billion dollars worth of gold came from these three sources, the first having produced twice as much as the other two put together.

The placers which still remain to be sought out and worked, offer a challenge to the ingenuity of the exploration geologist. The problems involve the following types of deposits :

152 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Placer rcacnrii

1. Deep gravel deposits lyinR immediately beneath several large rivers, such as the Feather and Klamath.

2. Isolated high benches such as those found in the Klamath Mountains.

3. Ancient gravels that lie beneath 'false bedrock' (interbedded volcanic layers) of the dredging areas along the western foot of the Sierra Nevada.

4. Gold-bearing gravels occurring in the 'shore' deposits of the lone (Eocene) formation, and the Chico (Cretaceous) formation.

5. Buried Tertiary channels and associated benches located in the known gold-bearing districts of the state.

6. Buried Tertiary channels and benches in the lava-covered district which lies between the Sierra Nevada and the Klamath Mountains.

7. Bajada placers, or desert alluvial-fan deposits, where gold is derived directly from the original mineralized bedrock source.

8. Desert placers, where the gold is reconcentrated from more ancient gold- bearing streams.

9. Buried desert stream placers.

The scope of these problems indicates the great need of an under- standing of the geological principles involved. In no kind of mining is geology more applicable than in the exploitation of these more obscure placer deposits. For this reason, the following discussion is written.

Significance of Improved Exploration Methods

A widespread geologic study of the ancient Tertiary gold-bearing stream channels of the Sierra Nevada, the gravel deposits of which are found to a large extent buried beneath a mantle of volcanic materials, was concluded by the United States Geological Survey a quarter of a century ago. Lindgren's "Tertiary Gravels'" summed up, in a splendid man- ner, in 1911, these various geologic studies. His data were drawn from his own careful observations, from those of his associates, II. W. Turner, F. L. Ransome, and J. S. Diller (issued largely in folio form), and from such early sources as J. D. Whitney, W. H. Storms, and Koss E. Browne.

Lindgren's Colfax folio, published in 1900, was the last great detailed field study of this kind in the Sierra Nevada. By no means, however, is this folio confined to the subject of stream channels, for it deals with every phase of the geology of the quadrangle. Everything of importance which it was possible to accommodate on a map of the small scale used — two miles to the inch — was recorded. At the time this field work was done, the best equipment and finest technique of the day were employed, and very little escaped Lindgren's keen observation, each fea- ture being scrutinized and shrewdly interpreted by his masterfnl mind.

Since then, however, considerable advance has been made in explo- ration technique; other and different points of vantage are now avail- able ; and a greater degree of refinement of study is therefore in order. Furthermore, mining itself has many advantages today over the earlier methods. With the recent enormous advances in development of motive power, pumps, and other machinery, the drift-mining industry could easily undergo a greatly accelerated development, if guided by intelligent exploration carried on in advance of the attempt to extract ' pay ' gravel.

' Lindgren, W., The Tertiary gravels of the Sierra Nevada of California : U.S. Ceol. Survey Prof. Paper 73, 226 pp., 1911.

'Lindgren, W., U.S. Geol. Survey Geol. Atlas, Colfax folio (no. 6G), 10 pp., maps, 1900.

Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 153

Aerial Photography. From the air, regional photographs are syste- matically taken by qualified aerial photographers. The pictures are then examined under tlie stereoscope, or used in constructing topographic maps Avhicli show the most amazing completeness of detail. Many sur- face features never before realized are thus simply unfolded before the eye. Geologic truths in great numbers are revealed, and many important problems solve themselves. Used as a base for location of field observa- tions and surface mapping, these aerial photographs are unexcelled They are undoubtedly the greatest practical aid which has yet reached the hands of the geologist ; besides they give secrecy, speed, and low-cost surveying to the program of modern exploration.

Geophysical Surveyinr/. Added to this regional view from the air is the greater insight into the very interior of the earth itself afforded by several types of geophysical instruments, now well-tried and stand- ardized. Peculiar characters of rock structure and composition are not only revealed but measured with precision by skillful engineers. Since the proper interpretation of all results thus obtained requires sound geologic reasoning, it is important that a better and more detailed back- ground of geology should be drawn, and this is made more effective by aerial photography.

Physiography. The subject of physiographic geology or geomor- phology has in recent jears made notable progress in developing sound, scientific principles concerning the history and origin of the present sur- face configuration of the earth. Since these principles are directly appli- cable to the more ancient earth surfaces of the Sierra Nevada, over which flowed the Tertiary streams now extinct. Tertiary physiography is the key to the ancient channel problem.

Study of Desert Processes. Recent study of the geologic processes at work in the desert has led to a better understanding of the desert placers, which offer a practically virgin field for exploration, holding a potential wealth not yet knowTi.

Stream Sedimentation. Furthermore, the study of sedimentation has now reached a refined stage of development. There are today avail- able various methods of technique which may be, but have not yet been, extensively applied to stream deposition. This sort of research includes the critical study of texture and structure of strata, as well as the micro- scopic examination of their mineral grains. It should yield a wealth of practical information concerning the processes involved in the accumu- lation of gravels, in the nature and direction of stream flow, in knowledge of what to expect as regards the concentration of gold and other heavy minerals, and in the correlation of channels of the same period or of the same system.

The more obvious criteria of stream sedimentation have long been used by the experienced miner, who, by examining the gold particles

' Lee, Willis T., The face of the earth as seen from the air ; a study on the applica- tion of airplane photography to geogrraphy : Am. Geog. Soc, Special Pub. 4, 1922.

English, Walter A., Use of airplane photographs in geologic qiapping : Am. Assoc. Petroleum Geologists Bull. 14. pp. 1049-1058, 1930.

Eliel, Leon T., Aerial photography and its importance to California geologists: California Div. Mines, Mining in California, State Mineralogist's Rept. 26, pp. 64-71, 1930.

Eliel, Leon T., Aerial photography proves its importance to California geologists : Oil Bull., vol. 15, pp. 1177-1181, 1253, 1929.

Haquinius, E., and Shuster, E. A., Fr., Construction and operation of the Huger- shoff aerocartograph : U.S. Geol. Survey, Section of Photo-Mapping, 1929.

I'Lackh Mining Kou Gold Ix California

[liull. l:!.")

Fin. 4S. View north(:'ast towanl Table .Mowitain, Tnulunme County, how this resistant lava flow, which filled a canyon cut in earlier vulcanic materials, now stands out in relief, while the surrounding cot'.ntry is eroded from its sides. Photo by Hurt Beverly.

under tlio simple liaiul lens, infers whether tiiey were robbed from earlier cliaiinels or whether they eame direetly from a vein. Also he uses tlie 'shingliufi' of <iravels to tell him the direetiou of stream flow. Tliese and a few other workiujr eriteria now used by the miner, however, have not all underjione a thorough seientific test, and at present thei-e is a wide differenee of opinion as to their interpretation.

The advanees in technique and sound geolop;ic interpretation should, therefore, be made to serve as wide practical aids in channel exploration, and much more definite and conclusive result.s should be {rained now than were possible 25 years ajro. Since it is well known that many channels still lie buried, undoubtedly containiuf]: a potential p:old wealth not yet half exhausted, why should not new discoveries now be made if the new teehnicpie in placer exploration is employed?

Certainly the more advanced methods of techni(|ue in exploration were called upon by the petroleum industry, resultino- in the floodinjj; of the country with oil. Now the application of some of the same methods is takinjr a leadino; part in various types of mining:, brinijiiifr further success to other mineral industries. If the prravel mining: industry takes full coofuizance of the importance of the new exploratory methods of the science, successes for it should indeed be assured.

Usefulness of Contouring an Ancient Surface

The most elucidatiufr method of tracing: in detail and showing graphi- cally tlie position and course of an ancient stream valley is by preparing a contour map of the old draina<re surface. The contours may be super- imposed over a base map which should also show the present surface topography and areal distribution of the geologic formations, as well as any mine workings, drill lioles, etc.

AVitli the old surface contours superimposed on the present surface contours, an accurate estimate may be made of the thickness, extent, and

" Lindgren, W., The gold-quartz veins of Nevada City and Grass Valley districts, California: U.S. Geol. Survey, 17th Ann. Rept., pt. 2, pi. II, 1896. (Contour map of Neocene bedrock surface.)

Sec. 11] CKOUKiY OF PLACKK DFPOSITS— JKNKINS loS

/n

B

Fir,. 49. A, Kffort of stream-bed irregularities on water current. After Chamber- lin ciiid Salisbury. B, SliiiiKliim'. The arrow points in the dirertion of stream flo\y. This arrangement of flat stones iiia.v be found in the bed of a mountain stream and is used by the drift miner to tell which way the ancient stream was flowing at that particular point. After Geike; orifiinalUi from Jamirson, T. G., Quarterly Journal, Geological Society of London, ml. ir,, /SoO.

yardag'e of the intervening cliannel-filled area. The points which are to be nsed in preparinfj; an old-surface contour map should be secured through careful study of geologic and physiographic conditions, and obtained during the surface and underground survey. Drill-hole data and the essential results of geophysical observations should also be rep- resented on this map. Careful enough study should be made so that the points used represent only one period of erosion.

If the geologic work is done prior to a contemplated geophysical survey and drilling program, much time and money may be saved in the location and number of points of observation, as well as in the number of drill holes needed. An approximate old-surface contour map may generally be constructed as a preliminary step by a skillful geologist, though he is limited only to surface data. This map should locate the general trend of the ancient valley to which later detailed work should be confined, thus eliminating much unnecessary and more costly work in adjoining areas unlikely to be productive. The most accurate elevations are those taken on bedrock where it is in direct con- tact with the older gravels, or with the pipe-clay and other volcanic materials of the oldest period of the area. Thus geological investigation should limit the extent of the geophysical work, which in turn defines the area to be drilled and later to be explored by underground methods.

The basis for such mapping may effectively be prepared as part of a plane-table survey of the surface topography and geology. Aerial photography, however, has now become an almost indispensable aid to such work. Enlarged aerial photographs may be used as plane-table sheets, thus adding to the final map an enormous amount of useful infor- mation and physiographic detail.

Provinces of the Ancient Channels in California

The .so-called 'buried channels' occur for the most part in the north- ern Sierra Nevada, where, during the Tertiary period, millions of years ago, volcanic outbursts with their mud-flows, covered the then existing network of stream courses. Thus entrapped and preserved, this old sur- face of the earth, probably Eocene in age, with all its forest-covered hills, beautiful valleys, and Avinding streams laden gold, 'became com- pletely hidden. Not until the area was lifted by mountain-making forces did the later rivers cut their canyons through the heavy mantle and expose whatever was beneath it. But even then, further volcanic mud- flows, cobble-washes, and newer streams of lavas, filled and refilled the

Mfi

rr.A( i:k Mixixr; for cold ix ("At.ifornia

Bull. 135

Fio. 50. Example of a Rcolngic map showing the earlier prevolcanic topog- raphy in contrast with tlx- prisent topography. Olii-surface contours (dashed lines) are drawn over prcent-siirfarH contours (fine, full lines). A major early Tertiary valley is thus reconstructed, ami the general position of its hurled stream channel is indicated, lying beneath volcanic materials of two later geologic periods, i.e., (1) Miocene cobble and pipe-clay (mud flows and lake beds), and (2) Pliocene lava flow which followed a canyon cut in the andesitic materials. The older chan- nel cut In bedrock is gold-bearing. Its course was controlled by bedrock, for it fol- lowed the contact between hard diorite and softer schist. The gradient of the lava flow is not as steep where it is directed south as where it turns toward the west. This is explained by the westward tilting of the Sierra Nevada.

Sec. 11] (iixiLocv oi' I'J;A(i;k |)i;i'()si'I's -.ii;.\1vI.\s LIT

valleys formed. Finally, modeni canyoii-outliii<j: trenclicd the whole area deeply. leavin<r remnants of ilat-topped ridges between.

Thonfzli no vok-anie mantle ever eovered the ancient streams of the Klamath Monntains, the ]-eion was uplifted in late Tertiary and Quater- times, and the rivers uere therefore entrenched. As a residt, benches of p:ravel were left at various elevations alon<? the sides of the canyons. Faulting- also played an important role in tiie history of the uplift, trappinj; <>old-hearing- pravels which date back to the Eocene." The whole .subje(;t of the sui-face features of the region, past and present, represents a series of vei-y interesting problems Jiot 3'et entirely solved, though they arc now- being carefully studied.

In the Mojave Desert,' Tertiary gold-bearing streams may have once flowed south from the region which is now the Sierra Nevada ; but during the Pleistocene period their deposits became so broken and disrui)ted by faulting, and so extensively covered by later desert wash, that now there renuiins little to be easily recognized or traced.

The problem of the 'dry i)lacer' is one of considerable importance, and when more is learned about it, an innnense potential gold wealth may be discovered which has not yet been glimpsed. At present, the lack of water is largely responsible for limited operations. It is quite possible, however, to find and develop a sufficient underground water supply in many places for dredging operations. The finding of such water sup- plies may also be greatly assisted through the use of geological knowledge and geophysical surveying.

In the Peninsular Ranges of San Diego County, some placers have been mined. In the Poway (Eocene) marine conglomerate is found the Ballena placer,'" described as early as 1893.

Economic Significance of tlie Tertiary Gravels

Lindgren'' in 1911, made the statement that "about $300,000,000 is a conservative guess for the amount obtained from the Tertiary gravels," including hydraulic, drift, and other forms of placer mining. Ju.st how much has been taken from the buried channels by underground metliods, alone, is difficult to determine. J. M. Hill '" states :

"Drift raining on the ancient buried channels was slarted at Forest Hill, Placer County in 1852 and was an important source of placer gold, by ISGG. During the period beginning about 187G and continuing to about 181)0, drift mining was most productive."

" Hinds, Norman E. A., ]Mesozoic and Cenozoic eruptive rocks of the souUiern Klamath Mountains, California: Univ. California, Dept. Geol. Sei., JJiill., vol. :iu, i). 3G8. 1935.

" Ilulin, C. D., Geologic features of the dry placers of the northern Mojave Desert : California Jour. Mines and GeoloKy, vol. oO, pp. 417-J2(i, 1!)34.

Simpson, E. C, Geology and mineral deposits of the Elizabeth Lake quadrangle, California : California Jour. Mines and Geology, vol. 30, p. 4 09, 1"J34.

0 Donnelly, Maurice, Geology and mineral deposits of the Julian district, San Diego County, California : California Jour. xMinos and Geology, vol. 30, p. 3ti:t, i'.r.'.r,.

1" Merrill, Frederick J. II., The counties of San Diego, Imperial: California Min. Bur., State Mineralogi.sts llept. 14, p. 052, 1'J14.

Fairbanks, H. \V., (Jeology of San Diego County, also portions of Orange and San Bernardino Counties: California 2Min. Bur., State Mineralogist's liept. 11, p. 'Jl, 18a3.

" Lindgren, \V., The Tertiarv gravels of the Sierra Nevada of California: U.S. Geol. Survey Prof. I'aper 73, p. 81, 1911.

12 Hill, J. M., Historical summary of gold, silver, copper, lead, and zinc produced in California, 1848 to 1920 : U.S. Bur. Alines, Econ. Iaper 3, p. 0, 1929.

I'LACKK MININn FOR fiOLD ( AI.I l( IKNTA

[Bull. 135

Ki

.Mil' -r

til.' II til.- I

II M.rni .\.v;i.l:i. lli.' KI:iiii;Uh M ..mil ;i ins. 111.. i:r.:it i:.isi .il. I liiis Im-.h mill,., I ill 111,- I', iiiiisiihii- l:,iiin,'S. ini.l ,i miimII aiiK.mit iKis I... 11 r,.mi,l ill 111,' siMitlurii (",.asl ll:iii;;,s. H was (itsf ,lis,'..v.i<'.l in 1 s:i I in (lu- Traiisv.Ts.- Ita n.-s .ast ,.r K.,s A-i.-l.-s; l.m ii..l imtil .laiii.s W. Marsha ll's -lis,-,. v.tv ..11 111,- Am.li.-aii in lli,- f,... thills ..I III.- Si.-iia .\.-\a,la. .1 iniiarv Ul, IS'IS, .lid 111.- ,.,-,nri-,ii,-,- ,.r t;,.|,l in falir,.riiia I., ni.- si;mli.-a r,l .

h'roiii 1.4S to l!):;;; ( 'jilironiia 's ])i-(i(liicl ion ninoimfcd to nearly Iwi) liillidii (l(.ll;irs. (.r wliicli (iiic .111(1 ;i (|iiiirtci- billion caiuc tVoni placer -I'avcl. 'I'Im" ratio of o-(,|,l pi-odiiccd from ]lac<M-s 1o <;-ol(l produiMvl from lo.lcs issJM.u,, in III,, lullowinu- table:

h'lili', ui ,,l„,-, r ),ii.<liirl„n, lo hnir l,n,il iirllun I'rr- I'liioil rent I'crlixl 1S4S l<. IN.-.U 100 ivji ,,, i,(()(,

isr.l I.. IMJO

1.S71 I.. I.SSd

1S.Si Isiw)

'.l!l I'.MM I., l'.l()_ IMII lo 1020. 70 1!L'I lu lO.'SO-

re, I

liO

Sec. Ill (ilX)LOGY OF VhM'VAl DEPOSITS — .IKXKINS 159

The decline in this ratio was eau.sed by tlie closing down of hydraulic mines In- the Sawyer Decision of 1S84 tojether with the C'aininetti Act of H'.)', as well as by the increased development of lode mining. The later increase of the i-atio was due to the use of the dredge, which was introduced in Califorjiia in 1898.

Haley" has estimated that "In the neighborhood of $600,000,000" worth of gold (on the basis of the old price) is still recoverable from the old Tertiary channels, referring to both hydraulic and drift-mining prop- erties. There are undoubtedly many unaccounted-for channels, such as those that lie buried beneath the extensive lava flows which occur in the region lying between the Sierra Nevada and Klamath mountains. Though most of these are not today available for mining, the channels along the margin of this area may some clay be reached. It is conceiv- able, however, that the reserves in buried channels throughout the Sierra Nevada, workable only through underground methods, should.be reckoned at least in terms of hundreds of millions of dollars.

The economic significance of the buried channel and the importance of its exploration should not, therefore, be slighted, for it represents a vast future source of gold wealth for California. The revival of the channel-mining industry is made still more interesting by an understand- ing of the detailed geologic features, the possibilities they suggest for certain of these buried stream courses, and the realization of the vast extent of the region yet to be explored.

Since an estimate of the potential wealth of the desert placers depends upon further exploration and mining of them, it is not yet pos- sible to evaluate their place in this study.

History of Development

The discovery of the Tertiary channels followed shortly after the discovery of gold in the present stream courses. In places, remnants of Tertiary channels were found lying exposed high up on 'flats,' stripped of their volcanic covering by Pleistocene erosion. Starting from these flats, the miners followed the uncovered channel to the point where it was covered by the lava capping, the top of which formed another kind of 'flat. ' Water was nearly always encountered, which led to the construc- tion of long and expensive drainage tunnels. To place these tunnels at the proper elevation to .serve their best purpose was the most serious prob- lem, for the old-timers did not have the powerful pumps which we use today.

The ideas developed concerning the courses and positions of the ancient channels were many and varied. Misconceptions of Tertiary physiography led many per.sons astraj, and millions of dollars were spent in vain. In spite of the millions gained, the losses were so great as to stamp this form of mining as hazardous in the extreme.

It is most instructive to follow carefully the recorded history of min- ing in a given district and to consider its relation to the geologic condition of that area. The two are so closely related as to provide a guide to the probable history which might be expected to be found in another area if the geology were known, or vice versa ; the recorded history reflects what geologic conditions may be expected.

13 Haley, C. S., Gold placers of California: Califurnia Min. Bur. Bull. 92, p. 5, 1923.

rLA<f;K MiNixf; lou coi.n in camfounia [Bull. 135

Fig. 32. Old work of tlie Valclor DredRing Company in the bed of the Trinity River, Junction City. l!<ii( h Kmvel exposed on the opposile side of tho cjinyon show.s the effect of early liydraiilic jniiiing.

Sec. TI] oEOT.or.Y of placer deposits — jenkins 161

Tlie geolofile liistory and structure of the buried channels are so com- plex tliat tlie best engineers have been baffled by them. Frafrmentary benches and sep:nionts of rich frravel deposits which still rest in posi- tions conijletely liidden from the surface, or even from the underground passages wliicli enter into the knver, main channels, afford alluring pos- sibilities to the geologist and geophysicist as well as to the prospector. A three-dimensional surface, complex and irregular in the extreme, is the problem to be faced.

The key to the solution is geology, aided by aerial photography, fol- lowed by new geo])hysical surveying, and finally by directed prospe<-ting through means of the drill, shaft, incline, or tunnel. To be effective, all these methods should be coordinated into one unified exploration pro- gram.

Classification of Placers Outline of Classification

A systematic geological study of placers calls for an orderly classi- fication dividing them into genetic types, which indicate how they were first formed. The following classification is based upon the fundamental conditions of deposition :

Fundaineiital clusaificatioii of iihncrs

A. Residual placer.s or 'seam diggings.'

B. Eluvial or 'hillside' placers, representing transitional 'creep' from residual deposits to stream gravels.

C. Bajada placers, a name applied to a certain peculiar type of 'desert' or 'dry' placer.

1). Stream placers (alluvial deposits), sorte<l and re-sorted, sinii>le and ci>:\- lescing.

E. Glacial-stream placers, gravel deposits transitional from inoraint's. for tlie most p.irt valueless.

F. Eolian placers, or local concentrations caused liy the renioxal of liglilcr nmti'- rials by the wind.

G. Marine or 'beach' placers.

Of these seven types, the ordinary stream i)lacer is by fai- tlic most important. All types are, however, more or less interrelated jind iiitci-- gradational ; they are all subject to deformation or burial, mikI tlicy m;i.\- be formed during any geological pei'iod.

Most of these various types of ])lacer (lei')()sits have been well described and classified by Brooks," ]\lertie,'' jind others '" in tiicir studies of Alaskan geology. Webber" recently ])i-oposed the luime, "bttjada placer" for peculiar desert, or so-called 'dry' i)lacers, which he carefully analyzed. The concentration of gold by the agency of witid in Western Australia has been described by Kickard ''" and Hoover."

"Brooks, Alfred H., The gold placers of parts of Stward 1 '. niiisula, AhisUa : TS Geol. Survey, Bull. 328, pp. 111-1:51), Uiits. . . . Miiu-ral icsourivs ..f .Maska. report, on progress of investigation.s in IIU.S : U.S. Ceol. .Siirvtv, lUill. 5111', j))). 27-;!l', r.il4.

"Mertie, .1. B., Jr., The occurrence of iiictallii'vrous rifposits in tlu- Yukon and Kuskokwim regions: U.S. (Jeol. Survey Bull. 7:'.:i. i))). ICd-lc,."), i!2:!.

1" Wimniler, Xorman I-i., Placer niining methods and costs in Alaska; I'.S. I!uf. Mines Bull. 2.59, p. 11, 1927. (Clas.silication of i)lacers.)

" Webber, Benjamin X., Bajada placers of the arid southwest : Am. Inst. .Miii. Met. Eng., Tech. Pub. .588, pp. 3-1 G, 1935.

"Rickard, T. A., The alluvial deposits of Western Australia : Am. Inst. >Iin. Met. Eng., Trans., vol. 28, pp. 490-.537, 1S98.

"Hoover, H. C, The superficial alteration of Western Australian ore-deposits: Am. Inst. Min. Met. Eng., Trans., vol. 28, pp. 758-705, 189 8.

PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Outcrop yy/Z-h

I I Grave/ sance

SCALE M r££r

Confoor /nferya/ 50

Fig. 54. A, Diagrammatic cross-section sliowing the transitional stages in the development of jilacer deposits : First, the quartz vein ; second, disintegration at tlit outcrop to form a residual placer ; third, formation of eluvial i)lacer by 'creep' of rosiilual material down tlie hill sloi)e ; fourth, deposition of \vatiT-\vi)rl<ert material as alluvium, forming an auriferous gravel diriosit, or stream placer. Sketch map showing development of rich i)lacers broken down directly from the disintegration of a gold-bearing vein ; after Lindyren, Mineral Deposits.

General Statement

111 valuatiiif a placer, one of the first considerations should be the detenu illation of how it was formed. It is reeoininended, therefore, tliat the exploration entrineer should classify frenetically each gravel deposit to be prospected. This calls for an understanding of the historical geology of the region and of the processes which have been responsible for the formation of the deposit, as well as how it came to be preserved or modified from its original form. The actual sampling of a deposit is carried on in a much more intelligent and satisfactory manner when a clear understanding of the geologic set-up has been acquired.

See. TI] fii:OLO(;Y OF PLACER DEPOSITS — JENKINS 163

Characteristics of the Principal Types of Placers Residual Placers

In order that olcl may become released from its original source in bedrock, the encasing material must be broken down. This is most effec- tively done by loni-continued surface weathering. Disintegration is accomplished by persistent and powerful geologic agents, which effect the mechanical breaking-down of the rock and the chemical decay of the minerals.

The surface portion of a gold-bearing orebody will become enriched during this process of rock disintegration, because some of the softer and more soluble parts of the rock are carried away by erosion, leaving the remaining portion of higher tenor. The name ' residual placer ' is applied to this type of deposit. After the residual portion is mined away by com- paratively inexpensive methods, the harder mineralized rock is encoun- tered, and the mining methods must be changed to accommodate another type of deposit, i.e., the lode.

The so-called 'seam diggings' are in weathered, gold-bearing quartz stringers, occurring along fracture zones of disintegrated schists.

Eluvial Placers

After gold is released from its original bedrock encasement through agents of rock decay and weathering, the whole weathered mass may 'creep' dovni the hillside (in some regions partly because of frost heav- ing) and may finally be washed down rivulets into gulleys. Lindgren states :

"When the outcrops of gold-bearing veins are decomposed a gradual concentration of the gold follows, either directly over the primary deposits or on the gentle slopes immediately below. The vein when located on a hill.side bends over and disintegration breaks up the rocks and the quartz, the latter as a rule yielding much more slowly than the rocks ; the less resistant minerals weather into limonite, kaolin, and soluble salts. The volume is greatly reduced, with accompanying gold concentration. The auriferous sulphides yield native gold, hydroxide of iron, and soluble salts. Some solution and redeposition of gold doubtless take place whenever the solutions contain free chlorine. The final result is n loose, ferruginous detritus, easily washed and containing easily recovered gold. This gold consists of grains of rough and irregular form and has a fineness but slightly greater than that of the gold in the primary vein."

On its way down the hillside, gold is sometimes concentrated in suf- ficient amount to warrant mining. Such deposits are classified as eluvial placers. They are transitional between residual and stream, or alluvial, deposits.

There have been a number of residual and eluvial gold deposits mined in both the Sierra Nevada and Klamath Mountains ; for example, the 'seam diggings' of Georgia Slides, El Dorado County, and Scott Bar, Siskiyou County.

Stream Placers

By far the most important type of placer is the ordinary alluvial gravel or stream placer. So far, it has been the source of most of the placer gold mined ; but now its supply is nearing depletion, save for values remaining in those ancient channels which lie deeply buried beneath a cover of lava or rock debris.

Lindgren, W., Mineral deposits, p. 213, McGraw-Hill Book Co., 1919.

Logan, C. A., Mother Lode gold belt of California : California Div. Mines Bull. 108, pp. 43-44, 1935.

22 Logan, C. A., Siskiyou County : California Min. Bur., Mining in California. State Mineralogist's Rept. 21, p. 474, 1925.

Placer .Mixing For Cold In California

[Bull. 135

Fig. Quartz Hill mine, Scott River, Siskiyou Cour.ty. DisenteKrated material formed in the upper part of gold-bearinK veins, by residual weatherins, has been re- moved by hydraulic mining. Note the terrace-like profile of the hill, indicating tliat an older, less rugged surface existed at the time this deep weathering took place. Uplifting of the region entrenched the drainage, and much of the gold released by weathering was washed by Pleistocene erosion into Scott Hiver where rich gravel bars have been mined.

Sec. II] GEOLOGY or PLACER DEPOSITS — JENKINS 165

Deposits by streams include those of both present and ancient times, whether the}' form well-defined channels or are left merely as benches. Stream placers consist of sands and jiravels sorted by the action of run- ninjr water. If they have underjrone two or more periods of erosion, and liave been re-sorted, the result will in ail probability be a comparatively high de<iree of concentration of the heavier mineral jains.

Quoting from Mertie :"

"All l)oiK-h placer.s, when fir.st laid down, were stream placers similar to those of the jiresent stream valleys. In the course of time the stream gravels, if not reworketl by later erosion, may he left as terraces or benches on the sides of the valley, if the local base-level is lowered and the stream continues to cut down its channel. Such deposits constitute the so-called bench gravels. On the other hand, if the regional or local l)ase-level is raised, the original placer may be deeply buried and a second or later placer deposit may be laid down above it. If the local base-level remains l)ractic.illy stationary for a very long period, a condition seldom realized, ancient and recent placers may form a perfectly continuous deposit in a long valley, for the deposi- tion of a gold placer is known to occur at that point in a valley where the stream action changes fmm erosion to alluviation, and such deposits are therefore formed progres- sively ni)stream.

"Where several parallel and contiguous streams that are forming placers emerge from their valleys upon an open plain, perhaps into some wide valley floor, a continuous or coalesc-ing placer may be formed along the front of the hills. "If the streams empty info some lake or estuary, a delta placer, genetically the same but perhaps different in some minor respects, may be formed. Manifestly such compound placers may be formed i>y either present or ancient streams and may be elevated or buried in the same w.iy as simple stream placers."

In order to understand thoroughly the subject of stream placers, streams tliemselves must be studied in regard to their habit, history, and charHcter. The effects of existing and changing climates, the relation to surrounding geologic conditions, and the effect of movements of the earth must also be considered. A special chapter in this report has therefore beeji devoted to a brief outline of the fundamental geologic features of streams.

Glacial-Stream Placers

It is a frequent fallacy of the placer miner to attribute the deposition of gold-bearing gravels to the action of glaciers. Contrary to such a belief, glaciers do not concentrate minerals; the streams issuing from melting ice, however, may be effective enough in sorting debris to cause placers to be formed under certain especially favorable conditions. In California, glaciers occurred througliout the high Sierra during the Pleis- tocene, but in Tertiary times they were wholly lacking. The Pleistocene streams cut through the earlier channels, robbing them of much of their gold.

Quoting from Blackwelder : "

"Since it is the habit of a laciei- to scrape oK loose debris and soil but not to .sort it at all, ice is wholly ineffective as an agency of concentration for metals. Gold derive<l from the outcrops of small veins is thus mixed with large masses of barren earth. Attempts to mine gold in glacial moraines, where bits of rich but widely scat- tered float have been found, are for that reason foredoomed to failure.

"If a glacier advances down a valley which already contains gold-bearing river gravel, it is apt to gouge out the entire mass, mix it with much other debris and deposit it later as useless till. Under some circumstances, hinvever, it merely slides over the gravel and buries it with till without (lisi\irliiiii; it.

Op. cit., pi>r 161-162.

Blackwelder, Eliot, Glacial ami ;iss(Kiat>-(l stitain ikpi.siis nf the Sierra Nevada : California Div. Mines, Mining in California, State .Mineralngistb Kept. 28, pp. 309-310,

Placer Mining For Gold In California

Bull. 135

57. Hyilraulicking a hijih bench-gravel depo.sit of the Trinity River, near Us confluence with the South Fork. Location : Salyer mines, pit No. .'i.

"On the other hand, the .streams horn of ghieiers or sh>\vly con.siiininK their moraines have the power to winnow the particles of rock and mineral matter according to size and heaviness. Such streams may form Kold placer deposits in the well-knowti way hy churning the load they carry and allowing the heavy minerals to sink to the bedrock. Placers may therefore be found in the deposits of jclacial rivers if there are gold veins exposed in the fjlaciated area upstream. Nearly all the gravel which has been dredged for gold along the foothills of the Sierra Nevada was deposited l)y rivers derived in part from glaciers along the crest of the range, but most of the gold was probably picked up in the lower courses of such rivers. Since glacial rivers choko themselves and Ixiild up their channels progre.ssively, their deposits are likely to he thicker and not so well concentrated as those of the more normal graded rivers which are not a.s.sociated with glaciers."

A few gold-bearing deposits in re-worked glacial till may be found along the eastern front of the Sierra Nevada, as, for example, in the region just north of Mono Lake on the road to Bridgeport.

Bajada Placers

The name 'bajada' was first used by Tolnian "" for confluent alluvial fans along the base of a mountain range. Recently Webber "" named and described the bajada type of placer deposit as follows :

"Bajada is the Spanish term for slope and is used locally in the Southwest to indicate the lower slope of a mountiiin range, the portion consisting of rock debris and standing at a much lower angle than the rock .slope of the range proper. ♦

"The total production of gold from l)ajada placers in the southwestern Inited States is neces.sarily .small, probably not over ten million dollars. ♦ ♦

"Most all bajada placer gravels are Quaternary and the larger part are recent.

"The genesis of a bajada placer is basically similar to that of a stream placer except as it is conditioned by the climate and topography of the arid region in which the placer occurs. ♦

"Erosion, transportati<jn and deposition in a region of extreme aridity present some phenomena not encountered in more humid areas. Practically all the work running water is strongly conditioned by aridity. ♦ ♦

Tolnian, C. ¥".. Erosion and deposition in southern Arizona bolson region: Jour. Geology, vol. 17, pp. 136-163, 1909.

"Webber, B. N., op. cit., excerpts from pp. 3, 4, 6, 8, 10, 11.

Sec. II] GEOLOGY OF PLACER DEPOSITS — .IF.XKIXS 1()7

Fig. 58. Cross-section of a Kold-bearing desert stream vallty ( .Manliattan, Nevada), showing the result.s of several periods of stream deposition from the old- est (1) to the youngest (6). Aiier Ferguson, U. S. (leol. Survey Hull. 7 2.1.

"Rock-floored canyons through which rock fratnent-s arc moved l)y infrequent torrential floods should con.stitute excellent pel)l)lp mills for the further reduction of the material, hut the amoiint of attrition accomplished seems to lie .sliRht, as fracmeuts, lare or small, on the hajada slope are decidedly anyidar and show little effect of attri- tion. Prohahly a small percentage of the (dd is freed durinj,' this phase of the movement of gravel. The gradient of the.se intermont drainage channels is too high to permit lodgment of the finer gravel. When a small amount of gravel is temporarily lodged in one of these channels, the deposit displays most of the characteristics of stream gravel.

"As dehris reaches the hajada .slope a rapid diminution in volume of water due to seepage and an extreme decrease in the grad( of channel causes deposition of dehri.s, and either (1) an alluvial fan or (2) a gravel-mantled pediment may he formed. If detritus is supplied to a hajada slope much faster than it can be removed, an alluvial fan is the result. jf i.,,(.k dehri.s is supplied to the hajada slope in consider- able volume but not in excess of the (piantity capable of transference to the center of the basin by the existing agencies, a gravel-mantle pediment results.

"The bulk of the gold that has been released from its matrix on the journey from lode outcrop to hajada slope is deposited on the hajada slope close to the mountain range. The gold is dropped along the contact of the basin fill and bedrock ; this is referred to hereafter as the lag line and is coincident with the line of contact of hajada gravels lying at a low angle and the rock slopes of the range standing at a high angle.

"The heaviest deposition of gold is on bedrock at the lag line, and since the lag line is moving in the direction of the crest of the range, values on bedrock may be dis- tributed over a large area of which the longest dimension is parallel to the foot of the range. Because bulk concentration does not operate as in a river channel, and a cer- tain percentage of the gold is still locked in fragments of matrix, to be partly released by further disintegration on the i)ajada slope, there is a strong tendency for less gold to reach betlrock and for more to remain erratically distributed throughout the detritus than in the ca.se of stream gravels."

There are probably many examples of typical bajada placers in the Mojave Desert and Great Basin regions of California, but recognition of them as such has not yet reached publication. Reconcentrations from former gold-bearing streams in the Mojave Desert have been described by Hulin '"' and dry placers in .southern California have been listed by ►Sampson.

Eolian Placers

Webber states that : "Bajada placers usually show an appreciable and even considerable enrichment on the surface due to removal of lighter material by wind and sheet floods." This applies to some of the dry

2" Op. cit.

Sampson, R. J., I'lacers of southern California : California L)i\-. Mines, Alining in California, State Mineralogist's Rept. 28, supplement, pp. 245-255, in;;2. Op. cit., p. 15.

KiS

I'LACCK MININC lOK COLO IN' fAr-II'ORNIA [.l:}3

'I'lacer mining in tlie beach sands at Santa Cruz, California, 1933,

placers of California, though no commercial eolian gold deposits such as those mined in Australia, previously referred to, are known in this state.

Wind action, however, is responsible for the removal of large amounts of fine detritus in the desert. The process involved has been called 'deflation' and its results described by Blackwelder." It is quite likely that it will be found to play an important part in the surface con- centration of desert placers.

Spurr" described "auriferous sand dunes" in the Nevada desert seven miles south of Silver Peak, 18 miles from the California boundary line.

Beach Placers

Concentrations of heavy minerals occur in various places along the Pacific Coast as a result of the action of shoie currents and waves, which tend to sort and distribute the materials broken down from the sea cliffs or washed into the sea by streams. The heavy minerals consist for the most part of magnetite, chromite, ilmenite, monazite, and zircon, with occasional fine particles of gold and platinum. Beach placers are of two kinds, (a) present beaches and (b) ancient beaches, elevated coast line is often found overlaid with terrace gravels which 'ere deposited at a time when the coastline was depressed. The beach placers of economic importance are those thatTiave been reconcentrated over and over again

Excellent descriptions of the geologic processes involved may %c found in reports on beach placers of Nome,"" Alaska, and of the coast

Blackwelder, Eliot, The lowering of playas by deflation: Am. Jour. Sci., vol. 21, r.th ser., pp. 140-144, 1931.

3' Spurr, J. K., Ore deposits of the Silver Peak quadrangle : U.S. Geol. Survey Prof. Paper 55, pp. 96, 97, 1900.

Mofflt, Fred H., Geology of the Nome and Grand Central quadrangles, Alaska : U.S. Geol. Survey Pull. 533, pp. 109-123, 1913.

Sec. II]

Geology Of Placer Deposits — Jenkins

Shora Shora - - - - i— - iTojs/ _Jq

s/'a'-'-"' --hde shore /,r,e.

Fig. 60. A. Diagrammatic cross-section illustrating the formation of beach placers in Alaska : njter CoWier aii<l Hess. U. S. Geol. Surrej/ Bull. S28. B. Cro.ss- .section of a tj'pical beach placer (Oregon) ; Pardee, U. H. Gcol. Survey Cire. 8. C, Diagrammatic cross-section of a coast, showing shore zones in an advanced stage of development; after Johnson; see Pardee, U. S. Gcol. Surieij Circ. X, UU.',.

of Orefon and California.' In discussing the origin of the gold in the Oregon beach placers, Pardee saj's :

"Some of the niiuens believe that the jjold of the he.iclies comes up out of the sea. an idea suggested by the fact that after a storm a formerly l)arren stretch may be found to be gold-bearing. This notion is true so far as the immediate source of .some of the gold is concerned. Materials composing the foreshore are carried out in the offshore zone at one time and returned to the beach at another. In the, process a shift up or down the coast may occur. Soundings of the Coast and Geodetic Survey show black sand to occur in the offshore zone at the present time. Gold and other minerals are <loubtless i)resent also. itor the beaches that border retreating shores, however, the nu)st of the gold and other minerals come directly from the-rocks that are being eroded by the waves."

The economic possibilities of mining the black sands of the California coast for their gold content liave long been discussed.'" Although gold and platinum have been the only minerals in the black sands which have been mined at a profit, much study has been given to the possible economic value of the other constituents."

Gold-bearing gravels of marine origin occur in the Chico (Upper Cretaceous) sediments of northern California. That they are marine in

Pardee, J. T., Peach placers of the Oregon c<ja.st : I'.S. f leol. Survey, Circ. 8, 1934.

Hornor, R. P., Notes on the black sand deposits of southern Oregon and northern California: U.S. Bur. Mines Bull. 19(i, 1918.

Pardee, J. T., op. cit., pp. 29, ZO.

Edman, J. A., The auriferous black .sands of California : California Min. Bur. Bull. 4.5, 1909.

Dav, D. T., and Richards, R. H., Black sands of the Pacific slope : Mineral Resources U.S., 1905. pp. 1175-1258, 1907.

PLAfKR MININT! FOR HOLD IX CALIFORNIA

[Bull, i;}.')

M:itfij;il iif this sort oiiio coxi loit most <il tlic iiidtliUi licit of the northern Sierra Nevaila. Location : 2 miles soutli of KniBlits Ferry, Tuolumne County.

()ririii and not fluvial is shown by tlieir content of abundant fossil sea- shells, as well as by the character of their strata. They were formerly wron<rly classed as "the gravel-filled channel of a IMesozoic river.'"* Gold-bearinjr jrravels have also been reported from marine sediments of the Lower Cretaceous of northern California.

Since the gravels of the Eocene rivers of the Sierra Nevada were richly gold-bearing, it is to be expected that some of the gold reached the sea. The sedimentary deposits of this Eocene sea are known as the lone formation. They occur along the "western foot of the Sierra Nevada.

Lindgren says : "'

"At the motitli of the rivers wliich descended from tlie IVrtiary Sierru Nevad.i extensive delta deposits were jiecuiniilated, and it is thus diflicult in many places to draw any exact line lietween the lone formation and the river gravels proper. The gravels in the formation are locally auriferous, though generally poor, hecause spread over large areas."

The deposits contain (juartz gravels aiul finely divided quartz grains; they are closely connei'ted with the oldest river-channel deposits; they occur along the extreme western foot of the Sierra Nevada. Therefore, as stated by Allen,*" the lone sediments

indicate delbi deposits formed at the mouths of many westward-flowing streams. The presence of marine fossils in the upper part of the lone formation shows that they accumulated on the shores of an Eocene sea."

The processes involved in the distribution and concentration of gold in the marine strata of both the Cretaceous and Eocene formations have never been carefully studied. If these marine and delta placer deposits have any particular economic significance, it certainly has not been ade- (luately demonstrated.

Dunn, R. h-, Auriferous conKlomerate in California : California Min. Bur., State AlineraloBisfs Uept. 12, pp. 4r)!(-471, map p. 461, 1894.

" Lindgren, W'., op. cit.. Tertiary gravels, p. 24.

Allen, Victor T., The lone formation of California : Univ. California, Dept. Geol. Scl. Bull., vol. 18, p. 348, 1929.

See. IT] GEOLOGY of placer deposits — JENKINS 171

Preservation of Placers

Placers are preserved if soniethiiif; keeps them from beinj? eroded away. Since streams are continually changing their positions, fragments of their deposits are often left isolated. Tn cutting a deeper channel, a stream leaves 'benches' or 'terraces' at different intervals along its valley sides; but erosion tends to desti-oy them, unless they are protected in some way.

Burial is the most effective way in which a placer may be preserved. The name 'buried channel' has often been restricted to streams covered deeply by lavas, mud-flows, ash-falls, etc., all of which were very common during the Tertiary period in the Sierra Nevada. There are, however, other means by which burial may be effected.

1. By eoveriiiK with liind.slide material. (An example occurs in Canyon Creek, Trinity County.)

2. By covering with travel, cau.sed by the fanlting-down of a part of the river system. (Examples are l)elieved to occur along; the Klamath, Trinity, and some of the larjcer rivers of the Sierra Nevada.)

3. By covering with like deposits. (Many of the l)uried Tertiary channels were covered first by lake sediments, called 'pipe-clay,' before lava or mudflows poured over them.)

4. By coverinR with gravels when the stream is choked. (Examples are common along stream systems.)

5. By covering with gravel when the stream course is lowered below the general base-level of erosion. (Examples of this case are found along the western foot of the Sierra Nevada.)

6. By covering of the bedrock surface of down-faulted blocks (graben) by .sedi- ments of various sorts. (Many examples, especially in the Great Ba.sin and Mojave Desert regions.)

7. By covering of older stream courses with alluvial fan material, as conditions favorable to stream existence fail. (Many examples in the Great Basin and Mojave Desert regions.)

8. By covering with glacial till. (Examples may be looked for in the glaciated areas of the Sierra Nevada.)

9. By covering of beach placers with marine sediments as the fluctuating coast is submerged, but later elevated. (Such as the present elevated beach placers which are in places covered with other marine se<liments.)

10. By covering of one geologic formation with another, through the processes of earth deformation and thrust-faulting. (In a geologically active region such as California, examples of this case might very well ie found.)

11. By submergence of river canyons to great depth beneath the ocean. (Off the coast of California many submarine channels have been discovered and mapped by the V. S. Coast and Geodetic Survey. One extends over 75 miles from the shore and attains a depth greater than 10,000 feet. These channels are too deep, therefore, to explore for placer gold. A reported recent project to operate a sea-going gohl dredge would probably have to do only with off- shore marine deposits and not submerged stream placers.)

To find gold-bearing stream chainiels, buried and preserved in such a manner that they may be profitably mined, is the challenge to the exploration geologist.

Modification of Placer Deposits

Placer deposits may be greatly modified in form and structure by earth deformation. The gravel content may also become firmly cemented

Davidson, George, The submerged valleys of the coast of California : California Acad. Sci., Proc. (3) vol. 1, no. 2, 189 7.

Reed, Ralph D., Geology of California (with references), p. 3, Am. A.ssoc. Petro- leum Geologists, 1933.

Shepard, Francis P., Investigation of California submarine canyons (abstract) : Geol. Soc. America Proc. 1933, pp. 107-108, 1934.

PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Fig. 62. Diagram showing a down-tlroppefl fault Mock (grahen) bttween tun upLifted fault blocks. Krosion cover.s the one with materials derived from tht- other.K. Streams cut in bedrock iirior to faulting ma\ thus be buried under the alluvium of the graben. After Davifi. Stale Miu(r<tl<)tji.st'.i Itrpt. >U. '

Via. <;.T. Ideal sketch showing bow a landsliiic may dam up a iiKnintain valley to form a lakf. Silt, sand, and giavils deposited in and on the edge of this lake will rnvi r tbv stream gravels in its bottom. .1//- Dm is. Slate MiiicialiKiisfii Uriit. .i'.i.

Sec. TI] r.EOLooY ok plackr i)i:r()S!Ts — -.ikxkixs 173

by intci-stitial deposition of mineral inattci-, such as by lime and iron ear- bonate. or silica, tliron-zli tlie action of infiltratinti' solutions. The older the ])lacer, the more apt it i.s to have been modified in these ways from its orijiinal form and attitude.

The reional tilt of the Sierra Nevada has increased the gradient of the Tertiary channels " (where tliey lie in the direction of the tilt) from 20 or 30 feet to the mile to twice, three times, or even several times that amount. Locally, tiltinji" has been even {greater. Tn places where the ancient channels lie opposite (lire(;tion to the tilt the ori<iinal !,n-adient may have been reversed. Often steep tilting' is accompanied by local faulting: of a few feet to .several hundred feet, (ienerally the down- throw is on the east side of the fault plane. Tn form, this is a replica of the action which took place and still is takinjr place alon<>- the eastern escarpment of the Sierra Nevada. Such displacements and chanjes in channel-firadient as well as in actual position of the channel, are impor- tant factors which greatly influence mining' procedure. They should be nnder.stood so far as .surface data will i)ermit, before actual mining is started in a given area.

In the Mojave Desert and Great Basin region, faulting and tilting liave been extremely active, greatly affecting streams antedating late Tertiar}- and early Quaternary periods.

The tiow of ground water through stream gravels, the former chan- nels of which have been blocked, cut off, tilted, or folded by earth move- ments, is a factor of considerable consequence when it comes to mining such placers. 5l yv '. "

Gold in Placers

Original Source of Gold ,,

The particles of gold found in placers originally came from veins and other mineralized zones in bedrock, irqm which they were released through surface weathering and disirttfegration of- the rock matrix. Though the original source may not in every case have been a deposit which could today be mined at a -profit, the richer placers usually indicate a comparatively rich source. long period of deep weathering, result- ing in separation and release of large quantities of gold from the bedrock, followed by a more active period of erosion, generally due to uplift, is an ideal condition for gold to be swept into stream channels and there to be concentrated into rich placers. Still richer deposits may be formed through reconcentration from older gold-bearing gravels.

These are the most important geologic conditions which have been found to exist in the various gold belts of the world, and particularly in the Sierra Nevada of California.

For the most part, the original source of gold is not far from the place where it was first deposited after being carried by running water. This is certainly true in both the Sierra Nevada and Klamath Mountains. The streams,|lo>ving through regions of metamorphic and intrusive igne- ous rocks threaded throughout by gold-bearing veins, were found by the early miners to contain auriferous gravels. But the more recent streams which have had only barren lavas to pass over, as in the volcanic covered area between the Sierra and Klamath regions, have proved to be barren.

Lindgren " states :

*2L,indgren, W., op. cit., Prof. Paper 73, pi. X, Profiles along Tertiary channels of the Sien-a Nevada.

Lindgren, W., Mineral deposits, p. 213, McGraw-Hill Book Company, 1919.

174 PLACER MINING FOR GOLD IN CALIFORNIA llllU. 13.')

"Tho Kroat majority of roUI placers liavo Ikmmi dcrivod fi<>tn tlif wcathfriti},' and disintegration of adrifermis veins, lodes, shear zones, or more irre;;idar replacement deposits. In many regions (he rocks contain altnndant joints, seams, or small veins in which the gold has been deposited with quartz. ♦ It is often stated that gold is distributed as fine particles in .schists and massive rocks and that placer gold in certain districts is derived from this source. Most of these statements are not supported by evidence, though it is not denied that gold may in rare instances be distributed in this manner."

Release of Gold from Bedrock

Without some wide.spread process of release from the quartz veins and rocks — vaults in which the metal was orioinally firmly held — gold particles could not have escaped to be transported as such by running water. Tiierefore, extensive rock weathering and decay over a long period of time is a primary factor of extreme importance. It has per- mitted the original source to contribute gold particles, large and small, to placer accumulations. The same gedlogic processes which form residual and eluvial or 'hillside' concentrations of commercial merit operate in the general release of gold from bedrock. - ,

The factors of prime importance in weathering are solution, changes of temperature, depth of water-table and therefore depth of oxidation, action of rain, effect of gravity, growth of vegetation, nature and composition of material acted upon, and degree of topographic relief. Rock weathering, especially complete disintegration down to thewater-table, rather than deep disintegration, is often more favored by tropical climates. This, however, is only one factor, and large areas of deep secular weathering are found in the north, in such places as Alaska, where placers are abundant.

The processes which take place in the separation of gold from bedrock are described in detail by Brooks,'* who says-.,

"The breaking down of the rock and the accompanying chemical changes of the constituent materials set free the gold, one of the relatively indestructible minerals, and this becomes intermingled with the other insoluble material. Clay dominates in the residual raa.ss, but if the parent rock contained quartz, this, too, usually remains, being probably the most refractory of all the common minerals toward purely chem- ical agencies. Mineralized vein quartz very commonly carries easily decomposed minerals, such as pyrites, and is therefore readily broken up, allowing the insoluble ingredients of the ore body, such as gold, to be set free. This process is hastened by purely physical agencies, such as frost and changes of temperature, which break ui the insoluide rock constituents. ♦

"As a rule, the changes in a rock mass brouglit about by weathering result in a very material reduction in its bulk.*" The loss of material by weathering among siliceous crystalline rocks, according to Merrill," amounts to more than 50 per' cent, and in the purer forms of limestone it may reach as high as 91) per cent. Pumpelly"' has estimated that in the limestone areas of the Ozark Mountains the residual material represents only from 2 to 9 per cent of the original rock mass. Such reductions in volume necessarily result in more or less concentration of any insoluble material that may have been disseminated in the parent rock. This concentration will be materially greater in the case of substances of high specific gravity, such as gold, than in that of the lighter minerals, for the former will have a constant tendency to .settle to the bottom of the loose material. On declivities gravity will accelerate the process and help to sort the material, producing in some places a rough

Brooks, Alfred H., The gold'placers of parts of Seward Peninsula, Alaska : U.S. Geol. Survey Hull. 328, pp. 125-127, 1908.

'' Merrill has shown that in certain changes by hydration there is an increase in bulk. He estimated that in the conver.sion of granite into soil (District of Columbia) there had been an increase in volume amounting to 88 percent. Compare Merrill, G. P., Principles of rock weathering : Jour. (Jeology, vol. 4, p. 718, 1896.

' Merrill, G. P., Rocks, rock weathering, and soils, p. 2.34, New York, 1897.

Pumpelly, Raphael, The relation of secular rock disintegration to loess, glacial drift, and rock basins : Am. Jour. Scl., 3d ser., vol. 17, p. 136, 1879.

Sec. II] GEOLOGY OF PLACER DEPOSITS JENKINS 175

strntificntion." This is a sociilar process and will pntcoed as loiij; as the rocks continue to disintegrate.

"It is evident that the effectiveness of all these agencies is proportional to the length of time in which they are operative. A laud mass must remain stable relative to sea level, for a long period of time to permit the accumulation of any considerable amount of residual material. Uplifts bring about renewed activities of the watercourses, and the residual mantle is quickly removed by erosion. It is evident that the conditions that are most favorable to the accumulation of residual material are those in which the land ma.ss is at or near ba.se-lev<'l when erosion is reduced to a minimum."

It seems that topographic and climatic conditions which existed during the Eocene period in tlie Sierra Nevada Avere favorable for the release of gold. Rejuvenated drainage at the close of the period swept the innnense quantities of gold, freed from the enclosing hard matrix into the early Tertiary stream channels ; and these, soon after, became buried and preserved by lake sediments, ma.sses of gravel, cobble- wash, volcanic ash, breccia, and lava flows.

Associated Minerals

Mineral grains that are very heavy and resistant to mechanical and chemical destruction accompany the gold in placers. The so-called 'black sands,' generally made up principally of magnetite, are well- known to the miner. A long list of the minerals found in sluice-box concentrates is recorded by the United States Bureau of Mines.' Besides magnetite, there are found titanium minerals (ilmenite and rutile), garnet, zircon, hematite, chromite, olivine, epidote, pyrite, monazite, limonite, platinum, osmiridium, cinnabar, tungsten minerals (wolframite and scheelite), cassiterite, corundum, diamonds, galena, as well as quiclilver, amalgam, metallic copper, bird-shot, bullets, hob- nails, penknives, watches, and nails.

Buried deeply in the gravels of the modern Feather River was once found (and someone thought it was an ancient fossil) the remains of a mule's hind leg wuth hoof and iron shoe nailed to it. What may be found in some of the placers of today may not, therefore, be repre- sentative of what was deposited by the more ancient streams.

The presence of quantities of magnetite associated with extremely fine gold particles, makes a difficult metallurgical problem. To the geophysicist, however, the presence of any minerals having a strong effect on the magnetometer is a godsend to effective exploration.

The determination of heavy minerals and their approximate relative percentage has been extensively iLsed in subsurface correlation of sedimentary beds in the oil fields, and tables have been developed for use in determining these minerals.'* The same method of research could well be applied to the tracing of channels. Though it has not yet been given consideration in California, this interesting field is open for study, with a well-developed technique available.

e Kerr, W. C, The gold gravels of North Carolina, their structure and origin : Am. Inst. Min. Eng., Trans., vol. 8, pp. 461-462, 1879-80.

Gardner, E. D., and Johnson, C. H., Placer mining in the Western United States. Part I, General information : U. S, Bur. Mines, Inf. Giro. 6786, pp. 15-20, Sept. 1934.

Tickell, F. G., The correlative value of the heavy minerals: Am. Assoc. Petro- leum Geologists, Bull. 8, pp. 158-168, 1924.

" Tickell, F. G., The examination of fragmental rocks, Stanford University Press,

**Raeburn, C, and Milner, H. B., Alluvial prospecting, the technical investigation of economic alluvial mineral*, D. Van Nostrand Co., 1927.

PLACER MIXIXG TOR COLD IX (ALlFnRXL\

Bull. 13i

Fig. G4. SUetoh map of an early Tertiary channel and its delta in the Kocene (lone) sea. The crosses indicate where llie gold has heen mined in the channel — on a bend in the stream, and at the iioint where a tribu- tary entered. Finely divided gold particles occur inter- bedded in lenses of quartz pebbles and sand lying above clay layers (false bedrock).

Fig. 65. Diagram to illustrate the course of a river, indicating where gold particles are most likely to become concentrated. After Spurr, U. S. Geol. Survey 18th Ann. Rept., 1898.

Sec. II]

Geology Of Placer Deposits — Jenkins

Fig. 66. i4. Diagrammatic cross-section showing the four principal ei)ochs of Tertiary gravel deposition in the Sierra Nevada. The deep gravels, a, represent Eocene ; b to d are successively younger and probably represent Miocene stages for the most part. The rhyolite ieriod is representid by c and the andesite by d. B, Diagram showing deposits in the Deep Blue lead, Placerville ; the older channel and benches of the inter-rhyolitic epoch are represented by a; rhyolite tuff, h; andesite cobble, c, andesite tuff-breccia, d; after Lindgren, U. 8. Geol. Survey Prof. Paper 7 J.

FiQ. 67. A, Diagram showing the place of greatest erosion on the bend of a river. B, Diagram to show positions of pressure and suction eddies in a river ; gold is more likely to be deposited in the suction eddy than in the pressure eddy. C, Diagram to show how a suction eddy is formed in a river; after Thomas and Watt; see Ries and Wataon, Engineering Geology.

178 I-LACKR MININC lOU COM) IN ( Al.l l( A |r.u11.l:'>

The soui-fc (f the iniiu'i-;il.s dopiisitcd jiiid associiitt'd with the partiek's lies in tlie rocks over which the stream has flowed. The source (f chroiiiite. i)latiiunii, and diamonds is <renerally attributed to helts of ser|)entine and irlated ultra-basic iMieous rocks, while <,Mruet, ilmenite ami marnetite miyfht come from metamorpliic rocks, and mona/it<>, zii-con. cassitcrite, wolframite, and scheelite would probably have their .soui'cc in rranite pe;zmatites. Transportation, Deposition, and Retention

The pi-ocesses of transportation and deposition of old in a stream ai"e apll\' stated by JJrooks:'''

'I'lic Inoisiiniliii;; IM.wci- :i slic;mi is .l.'i.riKlciil nil its vrlucily. which is ;i v.iri.iiit (Irininiii.Ml l)y ill.- fnidiciil, v..liiin.-, .mil l<.;i.l. Wltcii ;i sln-am is nv..rl.)a<h-<l Willi s.-(liiiiciil, llic excess is .lioppcd. When it is uiKleilo.ided, it erodes. When eiinililiriiiiii li.is lieen esl.ihlished, neither eiosiun nor deposition t.ikes place. Cr.idient, voliiine, .Old load usually vary in the s.iine stre.ini so th.it d<-position may he k'<'inK on in one i).irt of its valley .ind erosion in .mother. Wiien a stream is erodin;,', the material within reach of its .-ictivity is constnntly moved in a downstream direction. All m<ivements of (his kind are .-iccomplished hy more or less sortin;; and make for the concentr.it ion of the heavier i)articles.

"Deposition takes place in .a stie.im when the velocity is decre:ised, either liy the periodic chaii},'es in volume or hy a ch.iime of ;;radieiit. Whore there is a chanu'c of K'rade, resulting in diminished velocity, the 'old is laid down with the other sedi- ments. -It must he remembered, however, that placer .i;old may find lodgement in inequalities of the Ix-drock surface where no coiisidenihle deixisition of detrilal m.atter has taken pl.-ice, thoufih extensive placers are, as a rule, not formed hecause of irre>;ularities in the hed-rock surface ahine. The concent r:it ion of -old in river hars is analoj;ous to its deposition in stream he<ls. for it is dropped where the velocity of

the current is oheckod hy the form.-ition t>f eddies, due to the i pialities of the river

floor."

A further study of this subject is uuide herein in coiiiieetiun witli the more detailed analysi.s of stream action.

When tlie bed of a stream is the actual rock floor of the valley, it is called 'bedrock' in the true sense of the word. Later in its history tile stream may flow on an aggraded bed of gravel or other sediment. If the stream gravels become covered with volcanic or other materials, the stream is obliged to flow over this new cover, called 'false-bedrock.' Gold particles are normally deposited on or near the bed of the stream, which Is called 'bedrock' or 'false-bedrock' according to whether the bed is the true hard rock floor of the valley or whether it is a super- ficial layer of clay, volcanic tuff, or some such imjiervioius material overlying previotisly deposited gravel. It is readily surmised, .there- fore, that tliere may be two oi- more tiers of gold-bearing stream channels, but the ui)per ones do iiot necessarily lie directly above the older and lower chamiels, and may not follow the direction of their courses at all. If the .stream cuts clear down to the true bedrock, remnants of the older channels will lie at relatively higher positions instead of at lower hori- zons. In some cases, where gravel is deposited deeply on bedrock, forming a new aggraded bed, rejuvenation of the stream will .stir uj) the entire mass of gravels, including the gold-bearing layer deposited on top, and the final residt will be that most of the gold particles will reach a position very near true bedrock. The complexity of the history of thesQ processes is apparent; so also are the difficidties of the engineer who attempts to do a fair job of sampling.

Brooks, Alfred H., op. cit., p. 12S.

See. II] GEOLOGY OF PLACER DEPOSITS — .JENKINS 179

In excavating for the Boulder Dam a sawed plank of lumber was found 60 feet deep, ' ' lying under gravel on the edge of the inner gorge, a place that it could not have reached in any imaginable way except by burial during some comparatively recent flood." °" This case and many others show that the depth of burial by recent rivers does not necessarily mean that a great period of time has elapsed for the accumulation of the deposit. During high water, the whole ma.ss may be stirred up and even boulders floated in the soupy mixture of heavy rock debris and water. This action gives the gold particles a chance to work their way toward the bottom of the mass.

For thousands of years particles of gold of various sizes, from nug- gets to Hour gold, were dropped and lodged in the riffles of bedrock along the natural river-sluices of the Sierra Nevada. Flattened particles are most- easily carried; sometimes, suspended by air-films, tiny scales even float on the surface of the water."' Extremely fine grains of gold were swept by torrents through the canyons and out into the Great Valley. In the present dredging grounds where they are found, they have been easily caught in false-bedrock, which consists of clayey layers of volcanic tuff.'

The very high specific gravity of gold, six or seven times that of quartz, with the ratio increasing to nine times under water, is the primary factor which causes this heavy resistant metal eventually to work its way to a point where it may sink no farther. Once it is caught on bedrock, the stream has great dif!iculty in picking it up again.

When a stream leaves its mountain canyon and enters a more level country or a still body of water,, the materials carried by that stream are deposited in the form of a fan or delta. At the apex of this fan or delta fine gold may be deposited, and ma' never reach bedrock. It may be deposited on top of clayey, 'false bedrock' layers. The stirring action found to occur in rugged mountainous canyons during time of floods, which permits gold to reach bedrock, does not take place in the delta.

Lindgren state : ''''

"Bj- an odd paradox, gold is at the same time the easiest and most diflicult mineral to recover. It is divisible to a high degree and owing to its insolubility the finest par- ticles are preserved. A piece of gold worth one cent is without trouble divisible into 20<K) parts, and one of these minute particles can readily be recognize<l in a pan."

Although gold is verj' malleable, and may be hammered into differ-* ent shapes by stones hitting it as they tumble along in the stream, dif- ferent particles are not Avelded together to form larger nuggets, as some people are prone to believe. Lindgren" has sho\m that the largest masses of gold have come from lodes, not placers. Particles of gold may be broken down, however, from another piece. The more rounded or flattened nuggets have probably gone through more knocking about than the rougher pieces. Those showing the original crystalline forms have probabl}' not traveled far in the ' free ' state.

It is also found that the more ancient placers, and those which have undergone many reconcentrations, contain gold of a higher degree of fineness than those whose source is near by, or in which the gold has not

" Berkey, Charles P., Gorge excavation confirms geological assumptions : Eng. News-Rec, vol. Ill, p. 762, fig. 2, 1933.

" Lindgren, W., Mineral deposits, p. 220, 1919. 62 Lingren, W., Mineral deposits, p. 220, 1919. " Lindgren, W., op. cit., Tertiary gravels, p. 66.

PLACER mining; FOR COLD LV CALnX)RNIA

[Bull. 135

r=r

a

b

cf

Fig. (iS. Diagram to represent the theoretical effect of incroa.scd velocity (V) on transporting power (Toe) of a stream; uftcr ChumhcrXaxn and HdlisbiDii. TocV", i.e., if the velocity i.s doubled, the transiiorting power increases as much as (i4 times.

"A statement more frequently encountered is to the effect that the quantity varies with the sixth power of the velocity ; and the origin of thi.s assertion is now in doubt. It is an erroneous version of a deductive law. . . . The law, as formulated l)y Hopkins, is that 'the moving force of a current, estimated l)y the volume or weight of the masses of any proposed form which it is capable of moving, varies as the sixth power of the velocity' ; and this law pertains not at all to the (|uantity of material moved, but to the maximum size of the grain or pehhle or boulder a given current is competent to move." Gilbert, G. K., The transportation of debris by running water: U. S. Geol. Survey Prof. Paper 86, pp. 15-16, iyi.i.

Sec. II] GEOLOGY OF PLACER DEPOSITS JENKINS 181

been deposited for sueli a long period of time. This may be due to the removal of alloyed silver by the dissolvinj; action of surface waters."

The solution and reprecipitation of gold in the gravels is shown to be exceedingly rare or nonexistent, commercially.'*- On the other liand, in some of the Tertiary channels, thin crusts of pyrite or marcasite are found deposited on the surface of the gold particles themselves.

Factors of Concentration

A placer worthy of mining is like any other commercial mineral deposit in that it is a special case of concentration due to several com- bining natural processes which were all in favor of the accumulation of the one desired mineral. Source, release, transportation, deposition, reconcentration, and retention of the gold have already been discussed. Three extremely important factors are: (1) Structural control of the stream pattern, so that the streams run along the course of the zones of mineralization; (2) Decay and disintegration at the surface of the mineralized rocks prior to erosion ; (3) A change in the cycle of erosion, causing rejuvenated flow of streams and the rapid washing of the released gold into stream channels.

Quoting from a recent paper appearing in the Engineering and Mining Journal

"Accumulation of gold in an important placer deposit is rarely a mere coinci- dence ; it is rather the fortuitious concurrence of several favorable factors. In regions where nature has bestowed the advantages of extensive mineralization, rapid rock decay; and well-developed stream patterns, a relatively large amount of gold placer may be formed. But even in this ideal case, the favorableness of these several important factors must be assumed.

"The general considerations which favor the accumulation of gold in special locations have been frequently discussed. Physically, the phenomenon is simple ; in such locations where the gold has been deposited, the transporting power of the stream has become insufficient to carry away the particles of gold that have settled. The richness of the deposit will therefore depend not only upon the completeness of this loss of transporting power, and on the ability of the bedrock to hold the deposited gold at this point, but also, most importantly, on the general relationship of the gold sources to the stream. The early miners untiringly sought the 'ledge' or 'raothor lode' which furnished certain rich placers. However, with the presence of mineralized zones as a source of the gold, the richness of a placer is perhaps due more to the efficiency of the stream as a concentrating device than to its uncovering rich lode deposits.

"The ability of a stream to transport materials is essentially dependent upon the velocity of the water and the area and specific gravity of the particles of material being carried. The transporting power of water varies approximately as the sixth power of the velocity. This means that even small velocity changes have an enormous effect upon transporting power, ranging rather abruptly from velocities which can not transport an appreciable amount of gold to those which easily trans- port much of the gold that may enter the stream or be released from the gravels therein. The velocity of water is a complex relationship of grade, shape, and size of the channel, quantity of water, and other factors. A grade ranging from 30 to approximately 100 ft. per mile will favor the deposition of gold. With appropriate conditions of flow, these limits may be somewhat increased or reduced without serious handicap. When considering the grades of the ancient channels, however, one must remember that faulting and regional tilt often have considerably modified the original grade.

"For the richest accumulations, the erosional conditions must be well balanced, so as to provide a long period of concentration. Slight uplifts tend to rework and further enrich placer deposits, as do increased volumes of water, inasmuch as both of these factors tend to increase the velocity. Local variations in the shape of the

Lindgren, W., opf'cit., Tertiary gravels, p. 68. " Lindgren, W., op. cit., Tertiary gravels, p. 69.

Jenkins, O. P., and Wright, \V. Q., California's gold-bearing Tertiary channels: Eng. and Min. Jour., vol. 135, pp. 501, 502, November 1934.

I'LACKU .MININC FOR (iOIJ) IX CAI.irOKNIA [null. V\7)

Fig. 69. Ideal vertical section of a delta, show- ing in greater detail than figure "0 the typical succes- sion of strata : A, topset ; B, foreset ; and C, br)ttomset beds. After Gilbert, U. S. Gcol. Survey 5th Ann. Rent. 188S.

ro. Ideal cross-section of a delta showing A, topset ; fi. foresot ; and C. liottom- set beds. After Gilbert, U. S. Geol. Survey 5th Ann. Rept., 18H3.

Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 183

channel are of most interest, however, because they are immediately responsible for specific deposits of placer gold. When a stream canyon widens out, deepens, turns, or joins another watercourse, certain zones of concentration will be formed where (he water velocities have been somewhat reduced and where eddy currents occur. These reductions in velocity immediately allow >;old and heavy mineral particles to separate from the mass of gravel that is beinjr carried and rolled down the canyon. Gold has a specific gravity of approximately .six times that of the gravel, but under water this ratio becomes about nine times. This large gravity difference permits the gold quickly to work its way to bedrock and into any crevices therein. Here it remains, requiring excessive erosion to remove it to new locations.

"In order that a major deposition of gold may occur, there must be an abundance of source material which contains more or less gold and which may be more or le.ss easily eroded. A decayed formation of low-grade material could easily furnish more gold than a hard, higher-grade deposit. The decomposed material also supplies more gravel for balanced conditions of stream transportation, providing that overloading or choking is minimized by uplifts or increasing water volumes. Plainly, a stream running along a vein system will have a greater opportunity to accumulate gold than one merely crossing it. Bedrock-controlled streams, therefore, provide a maximum contact with source material.

"A further and very important factor is the ability of bedrock to hold the deposited gold in spite of the .scouring action of the stream at higher water stages. A smooth, hard bedrock is a very poor one for placer accumulations. Bedrock formations which are decomposed or possess cracks and crevices are good, and thos( of a clayey or of a schisto.se nature are excellent in their ability to retain particles of gold.

"Gold tends to resist most stream transportation. Coarser gold will migrate downstream an amazingly short distance from its apparent source throughout a long erosion period. The fine gold, which the stream can transport, is dropped rather completely within a restricted area at the mouth of the stream canyon."

Age of Placers Significance

The geologic age of a placer deposit is often a factor of primary economic interest. In the Sierra Nevada, the oldest system of Tertiary channels has proved to be the richest, for it was formed prior to the extensive volcanic activity which resulted in the covering of the min- eralized bedrock surfaces as well as the valleys in which gold-bearing streams flowed. These streams, which cut directly through the mineral- ized zones, had an ideal opportunity to tap the primary gold resources of the region, while those which flowed only over a barren volcanic cover remained themselves barren of gold. In the region of the buried channels of the Sierra Nevada, many stream deposits of different jjeriods are now found intermingled. To decipher their history and relative age is an essential part of the exploration geologist's work, in his search for the channels of greatest possible economic consequence.

Structural Criteria

Various criteria are used in determining the relative age of stream deposits, but the most positive evidence is structural relationship. For example, the cutting chaiuiel is younger than the channel which it cuts.

The deepest channel is not necessarily the oldest nor yet the youngest. In the case of the modern canyons of the Sierra — the youngest are the deepest ; yet along the western foot of the range the present streams floAv over older channels buried beneath. "Where a canyon is filled with detritus or with lava, the newer stream flows on top of the deposit and is therefore higher than the old stream-bed beneath, while still more ancient stream terraces or benches may lie at higher and varving elevations on either side of the canvon. Some

184 PLACER JIIXIXG P'OR GOLD IN CALIFORNIA [Bull. 135

benches, representiii}; former streams, may liave even been left prior to a lava tlow eoverin<; the deepest clinnnol, while other benches may have been left later.

It is a]iparent. therefore, that the subjects of historical sequence jind relative are matters of detailed jreolojric and physioM-aphie study which deserve more than superficial examination. They cainiot be classified by do}rmatic rules.

Paleontologic Criteria

In order to assijin definite jreolojric periods to the deposits of ancient streams, their ajre should be related in some way to the well- established epochs of rejiional jreolojric history. Fossils, diarnostic in determination of p-eolojiic periods, if found in the stream deposits, are of inestimable value in this rep:ard.

In the Sierra Nevada, parts of fossil plants consistinjr of leaves, lo<rs. etc., have been extensively collected and determined by paleo- botanists. Also, some vertebrate bones have been sent from the old drift mines to the Smithsonian Institution and elsewhere for scientific study.

fJeolojric periods the Avorld over have been established larp:ely on their marine fauna rather than their continental fiora or fauna. For instance, marine beds of the Tone formation contain fossil sea-shells definitely assijrned by iialeontolo<rists to the Eocene, or earliest Tertiary l)eriod. Tiie fossils found in the sediments filling- the Tertiary valleys of the Sierra are iiot, however, marine, but are of ancient lands and lakes. Correlation of jieoloiTric ajze by means of these land plants and land animals brings in complications that have not yet permitted the two bases of criteria, marine and nonmarine, to be perfectly coordi- nated. Besides, most of the fossil leaves occur in tuffaceous lake beds that overlie the frold-bearinjr quartz-jri'avel deposits, aiul therefore do not yive much direct evidence as to tlie a<re of the latter. Fossil wood. so common in the most ancient of the <::old-bearinr u ravels is not as yet determinable nor diaji-nostic. In most cases it represents unstudied tropical forms which have been placed in the Eocene by paleobotanists because of the known climate of that period. The older jrravel con- tainin<r this fossil wood has i)reviously been referred to the Cretaceous. In the Smartsville (|uadran<rle, for example, a deposit containin<r pet- rified lofrs of probable Eocene ajre is described by Lind<iren as follows:''

'Tli' hiKli. is()liitMl jirca of \v'll-\viisliM(l .S miles north-iK. of Montezuma Hill is Ilote\. ; it is so much liiuher than the adjiu-eiit uravel channel of North San .Tn.in that it must be assumed to Itelonn to an e.irlier period ; very likely it is of Cretaceous age."

It is a fact, however, that no fossils indicating- a Cretaceous ajre have yet been found in these older jrravels. Wherever definite marine Cretaceous beds do occur on the western foot of the Sierra Nevada the oldest stream channels of the vicinity are fouid to cut the Mesozoic .sediments, showinjr a profound difference in ajre between the two.

Chaney sunnnarizes the results of i)aleobotanical study of the fossil plants found in the Sierra Nevada as follows:

LiiKlnren. W., op- <it., TiTtiary uravvls, p. 12.

'""Chaney, Ralph \V., Notes on occurrence and age of fo.s.sil plant.'< found in the auriferous travels of Sierra Nevada : California Div. Mines, Mining in California, State Mineralogists Rept. 28, p. 301, 1932.

Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 185

"The tiiflfs and shales in which fossil plants occur interbedded in the Auriferous Gravels range in age from lowermost Kooene to upper Miocene. During this time, there was a climatic trend from suhtroiiical to temperate conditions, which resulted in the elimination of palms :iud other large-leafed species .Mnd the incoming of types of jdants similar, in general, to those now living in Xorth America. The Miocene flora indicating ;i temperate climate, includes genera no longer living in western America, although they occur in e;istern America and eastern Asia. 'JMie evidences of <lifference in living conditions in the Koceiie and t]i(> .Miocene make it possible readily to dilTerentiiile iietween the older and the younger floras of the Auriferous Gravels."

Mo.st of the fos.sil vertebrate bones de.scribed from the drift mines of the Sierra Nevada have been collected and sent in to paleontologists by persons who did not record their definite location, so that the exact geologic formations in which the fossils were embedded are unknown.

The paleontologist who works with vertebrate remains is not always apt to apply the same age to beds as that which has been assigned them by the paleobotanist ; generally the former assigns a younger age. lany of the well-established Sierran Tertiary as well as later beds containing vertebrate bones were once given the blanket designation of Pleistocene.''

Physiographic Criteria

Age correlation has sometimes been done purely on physiographic evidence. Matthes assigns Eocene, Miocene, Pliocene, and Quater- nary periods of uplifts to the various old surfaces found in the Yosemite region, tying in the Miocene surface correlation with geologic features of a fossil leaf locality occurring in the Tuolumne Table Mountain region. The fact that old surfaces have been resurrected during the Pleistocene has only recently been given consideration.

"Quaternary erosion resulting in the uncovering of Tertiary volcanic ash and the resurrection of early Tertiary surfaces, formerly cut into pre-Cretaceous bedrock along the western flank of the Sierra Nevada, is a widesjjread geologic process which has heretofore not received the recognition it deserves. The process inv<dves features of vast economic concern. One key locality for this study is in the region of Table Mountain, Tuolumne and Calaveras counties, California, where a very resistant late Tertiary latite flow has served the purpose of preserving not only fragments of earlier and less resistant geologic bodies consisting of volcanic materials, mud flows, lake beds, and stream gravels of different ages, but also the underlying bedrock surfaces of earlier Tertiary age. These ancient surfaces, the topography of which appears to have been controlled by bedrock structure, may be (ound in various stages of resurrection. In this are.a, the gold-bearing gravels were mined in ancient chan- nels that ran in directions opposite or at an angle to the Table Mountain Channel ; the latter apparently never contained any appreciable amount of gold-bearing gravel, contrary to the common belief. Though unmantled and dissected through Pleisto- cene and Recent epochs, fragments of upland peneplained bedrock aiul in places gravel-covered surfaces are actually early Tertiary land forms, which have been brought to light after having been buried throughout later Tertiary volcanic epochs."

Lithologic Criteria

The nature and composition of the material filling the ancient channels and valleys also indicate to what geologic period a deposit may belong. Gold-bearing gravels, composed purely of sand and quartz-pebbles, or of the bedrock complex, indicate that the channel

Hay, Oliver P., The Pleistocene of the western region of Xorth America and it3 vertebrate animals : Carnegie Inst. Wash., I'ub. 322-B, 1927.

"" Matthes, Francois E., Geologic historv of the Yosemite Valley : U. S. Cenl. Sur- vey, Prof. Paper 160, 1930.

"1 Jenkins, Olaf P., Resurrection of eaiiy sui-faces in the Sierra Nt- vada : California Jour. Mines and Geology, vol. 30, p. 5, 1934.

Placer Mining For Gold In California

[Bull. 135

is of the pre-volcanic period, possibly Eocene in age. Mo.st of the rhyolites were apparently formed during the latter part of this period and in the Oligoeene. The most abundant of the volcanic rocks are composed of andesites, which seem to be largely of late Miocene or early Pliocene age. During the late Pliocene and early Pleistocene there were many basalt flows. Tuolumne Table Mountain is composed of latite. probably of late Pliocene age.

In the Recent period much pumice has been expelled from craters and blown over various parts of the Sierra Nevada.

Streams may always be considered younger than the rocks from which tlieir gravel has been derived, though mud-flows may receive their materials from active volcanoes. There is here an opportunity for a petrographic study of both volcanic rocks and the materials of the sediments. Special detailed analysis of stream correlation might be performed by means of the method known as "heavy mineral separa- tion," previously mentioned as widely employed in petroleum geology.

Coordination of Criteria

In order to assign a geologic age to a placer, all criteria should be sought out and used so far as it is possible. A regional study of age relationship should include a coordinated study of all phases: struc- ture, fo.ssils, surface features, and materials deposited.

The principal placers in California occur in the Quaternary, Tertiary, and Cretaceous geologic time divisions, which are grouped in the following manner :

Eba

Cenozoic

Period Quaternary

Tertiary

Epoch Recent

Pleistocene

Duration

in millions

of years

(Neocene 1 Pliocene

or Xeogene) J Miocene

IniiKocene Eocene

I Cretaceous 75 Jurassic 40 Triassic 40

Paleozoic 415

Proterozoic Unknown

Life History and Habit of Streams Need for Scientific Background

p]xploration of placers and various ancient stream channels requires an understanding of the habits and life history of streams in general This includes, on the one hand, processes of erosion and deposition and on the other, physiographic history. Each is iinportant; the first more directly, while the second has to do with regional features, knowl edge of which is essential to the exploration geologist. The funda

Sec. II] OKOLOGY OF PLACKR DEPOSITS JENKINS 187

mental science of streams has been outlined in a simple yet splendid manner by G. K. Gilbert"- in his masterpiece on the Henry Mountains, Utah. Later, I. C. Uussell published an excellent text on streams.®

Such natural processes as those related to streams are so universal that a study of them in one part of the world may be applied to con- ditions found in another. Similarly, an understanding? of the ancient Tertiary streams of the Sierra may be jjained by applying the knowl- edjre of processes found in operation today where conditions and envi- ronments would appear similar.

In a province, such as the Sierra Nevada, where the development of the drainajre system has been repeatedly interrupted by earth move- ments or by burial as a result of volcanic mud washes and lava flows, the history of the stream of any one chronological horizon is a separate entity, and may be entirely different in form and pattern from either earlier or subsequent systems. This fact, together with the complexity of any one system presents a problem much involved.

The need for a scientific background in the study of streams is therefore apparent. The more pertinent features of this study, together with its terminology, are outlined in the following pages.

Stream Erosion

Stream or fluvial erosion is complex. It may be divided into the several processes: hydraulic action, abrasion, solution, and transporta- tion. A brief statement of the essential factors which control erosion is quoted from an authoritative textbook'* as follows :

"The capacity of a stream to erode depends on its volume and velocity. The velocity in turn depends on (1) the slope down which the stream is flowing, (2) volume of water, (3) the shape of its channels, and (4) weight and volume of its load.

"The rate of descent nf the bed of a stream is the stream gradient. It is ordinarily expressed as so many feet per mile. The gradient changes from place to place along the course of the stream. Velocity increases rapidly with increase of gradient. Thus mountain streams with high gradients erode their valleys much more quickly than lowland streams of comparable size with low gradients. It follows that streams wear high gradients down to low ones by continued erosion, and that as the gradients are worn down the rate of erosion must decrease.

'"The volume of water is a variable factor in all streams, largely because of fluctuations in rainfall. Velocity and rate of erosion in any stream are therefore always changing. As a rule, these changes are too slight to be readily noticeable, but in some regions they are great enough to cause streams to dry up at certain seasons, and to rise in floods at others. In other regions fluctuations are less extreme. Every spring the lower Mississippi has a normal rise in water level of 15 to 20 feet. The Nile normally rises 24 feet and the Ganges 32 feet. The erosive effect of such floods is considered below.

"The shape of the stream channel as seen in cross-section also influences velocity. Since friction between water and channel slows a stream down, velocity is greatest in channels with the smallest area in proportion to volume of water. Deep, narrow channels therefore give -greater stream velocity than broad, shallow ones.

"A stream continues to acriuire a load until it is carrying the greatest possible amount permitted by the gradient, volume of water, and kind of material available."

The "laws of erosive power" concern both transportation and abrasive power of the stream. If all the fragments of rocks had the same specific gravity, then the folloAving definite action would take place.

Gilbert, G. K., Report on the geolog> of the Henry Mountains : U. S. Geog. and Geol. Survey of the Rocky Mountain Region, Chap. V, Land Sculpture, pp. 9 9-150, 1877.

Russell, Israel C, Rivers of North America, a reading lesson for students of geography and geology, V. Putnam's Sons, 1S98.

Longwell, C. R., Knopf, A., and Flint, R. F., A textbook of geology, pt. 1, physical geology, pp. 42-44, ohn Wiley & Son.s, 1932.

188 PLACER MIXING FOR GOLD IN CALIFORNIA [Bull. 135

"If the volocity of a stream l>c doubled, tlie diameters of rock fratjments it can move are increased 4 times. In other words, the majimuin lUnmcler of the individwil rock frngments a stremn cnn move varies ns the siiunre of the retocity. Calculations have shown that douhluig the velocity of a stream increases its abrasive power at least 4 times, and under certain conditions as much as 04 times. In oth-r words, nhranive power varies hetueen the sijunre and the sij-th pouer of the velociti/.

"These laws not only explain the vastly jjreater erosion accomplished by swift streams than by slow ones under normal cttnditions, but they show clearly why exceptional Hoofis, greatly increasing velocity by increasing volume, have such tremen- dous destructive power. The volume of the Colorado Uiver measured at Yuma, Arizona, during a fiood in 1021, was l." times its normal volume. Again, when the St. Francis Kam near J-os Angeles gave way in 1!2S :ind Hooded the valley below, huge blocks of concrete weighing up to 10,t)(K) tons each, were moved by the escaping water. In India, during the (;ohiia Hood of ISl)."), which lasted just four hours, the water picked up and transported such quantities of gravel that through the first V.i miles of its course the stream made a continuous gravel deposit from 50 to 234 feet."

Preparation of Material Removed by Erosion

As previou.sly stated and described, tlie materials which are removed and washed into the streams are first prepared through weathering processes. Particles are loosened from the outcrop by surface disintegra- tion, consisting largely of oxidation, h'dration, and solution.

Since climatic environments were different in the past than they are now, the subject of ancient climates'' is an important problem in its relation to the development of ancient stream channels. The study of fossils imbedded in the deposits gives the most important clue to the nature of ancient climates. The condition and composition of the sedi- ments themselves give another, as repeatedly pointed out by

Transportation

Tlie subject of river engineering brought forth at an early date much definite information as regards the carrying power of streams. The following statement is quoted from Stevenson

"The following are results deducted from experiments made by Bossut, Dubuat, and others, on the size of detrital particles which streams flowing with different velocities are sai<l to be capable of carrying:

in. per sec. — 0.170 mile per hour, will just begin to work on fine clay. (J in. per sec. — 0.340 mile per hour, will lift fine sand. S in. per sec. — 0.4545 mile per hour, will lift sand as coarse as linseed. 10 in. per sec. — 0.5 mile per hour, will lift gravel the .size of peas. 12 in. per sec. — O.OSID mile per hour, will sweep along gravel the size of beans. 24 in. per sec. — 1.30.38 miles per hour, will roll along rounded pebbles 1 inch in diameter. 3 ft. per sec. — 2.045 miles per hour, will sweep along slippery angular, stones the size of a hen's egg."

The following table is quoted from F. C. Gilbert* to show the maximum diameters of boulders which can be moved in sluices at certain velocities:

"'Smith, J. p., Ancient climates of the West Coast: Pop. Sci. Monthly, vol. 76, pp. 478-486,1910. . . . Climatic relations of the Tertiary and Quaternary faunas of the California region : California Acad. Sci., Proc, ser. 4, vol. 9. pp. 123-173, 1919.

"" Reed, Ralph D., r.eology of California, Am. Assoc. Petroleum Geologists, 1933.

" Stevenson, Oavid, The principles and practice of canal and river engineering, p. 361, lOdinburgh, 1886.

(Gilbert, F. C, Design of sluices for gold placer mining : Eng. Jour., Arizona, vol. 16.no. 8. p. 4, 1932.

Sec. II] OEOLOOY OF PLACKR DEPOSITS — JENKINS 180

Diameter olocity

6 G.2

10 : 8.4

lo 0.1

1(5 lO.S

30 y-''"*

Trausportalioii, as sliuwii by Medoe,'"' is done by tlie carryiii<; of materials in solution, through suspension, and by tiie process of saltation. The materials thus carried are deposited by precipitation from solution, sedimentation from suspension, and grounding after 'leaping' along by that process called 'saltation.'

It lias been shown by (1. K. Gilbert,'" who carried on extensive laboratory experiments with running water, that the materials borne in suspension are easily enough sampled and tlieir quantity measured ; but the 'bed load' is much less accessible. This load is carried forward by sliding or rolling along a smooth channel bed, as well as by saltation, which takes place when the bed is uneven and causes the particle to move irregularly in a series of jumps.

Gilbert calls the transportation of the bed load "hydraulic traction" in contrast to "hydraulic suspension." His summary of "Modes of transportation, collective movement" is expressed as follows:

"When the conditions are such that the bed load is small, the bed is molded into hills, called dunes, which travel downstream. Their mode of advance is like that of eolian dunes, the current eroding their upstream faces and depositing the eroded material on the downstream faces. With any progressive change of condi- tions tending to increase the load, the dunes eventually disappear and the del)ris surface becomes smooth. The smooth phase is in turn succeeded by n second rhythmic phase, in which a system of hills travel upstream. These are called antidunes, and theirmovement is accomplished by erosion on the downstream face. Both rhythms of debris movement are initiated by rhythms of water movement."

In showing how complicated a stream 's action may be, Gilbert states :

"The flow of a stream is a complex process, involving interactions which have thus far baflBed mechanical analysis. Stream traction is not only a function of stream flow but itself adds a complication. Some realization of the complexity may be achieved by considering briefly certain of the conditions which modify the capacity of a stream to transport debris along its bed. Width is a factor ; a broad channel carries more than a narrow one. Velocity is a factor ; the quantity of debris carried varies greatly for small changes in the velocity along the bed. Bed velocity is affected by slope and also by depth, increasing with each factor; and depth is affected by discharge and also by slope. If there is diversity of velocity from place to place over the bed, more debris is carried than if the average velocity everywliere prevails, and the greater the diversity the greater the carrying power of the stream. Size of transported particles is a factor, a greater weight of fine debris being carried than of coarse. The density of debris is a factor, a low specific gravity being favor- able. The shapes of particles affect traction, but the nature of this influence is not well understood. An important factor is found in form of channel, efficiency being affected by turns and curvature and also by the relation of depth to width. The friction between current and banks is a factor and therefore likewise the nature of the banks. So, too, is the viscosity of the water, a property varying with temperature and also with impurities, whether dissolved or suspended."

60 McGee, W. J., Outline of hydrology : Geol. Soc. America Bull. 19, p. 199, 1908. "" Gilbert, G. K., The transportation of dfibris by running water : U.S. Geol. Survey Prof. Paper 86, pp. 10, 11, 15, 16, 1914.

190 PLACER MINING FOR GOLD IX CALIFORNIA [Bull. 133

Gilbert classifies streams according to their transportational char- acters :

"The classification of streams here Riven has no other purpose than to afford a terminology convenient to the sul)ject of (K'bris transportation.

"Wiien the (l<'bris supplied to a stream is less than its capacity the stream erodes its bed, and if the condition is other than temporary the current reaches bedrock. The dragging of the load over the rock wears, or aiirades, or corrades it. When the supply of d'bris equals or exceeds the capacity of the str'am bedrock is not reached by the current, but the stream bed is constituted wholly of debris. Some streams with beds of debris have channel walls of rock, which rigidly limit their width and otherwise restrain their development. Most streams with beds of debris have one or both banks of previously deposited debris or alluvium, and these streams are able to shift courses by eroding their banks. The .several conditions thus outlined will be indicated by speaking of streams as conadhifi, or lock-icnlled, or alluvial. In strictness, these terms apply to local pha.ses of stream habit rather than to entire streams. Most rivers and many creeks- are corrading streams in parts of their courses and alluvial in other parts.

"Whenever and wherever a stream's capacity is overta.\ed by the supply of debris brought from points above a deposit is made, building up the bed. If the supply is less than the capacity, and if the bed is of dbris, erosion residts. Through these processes streams adjust their profiles to their supplies of debris. The i)rocess of adjustment is called gradation ; a stream which builds up its bed is said to aggrade and one which reduces it is said to degrade.

"An alluvial stream is usually an aggrading stream also; and when that is the case it is bordered by an alluvial plain called a flood plain, over which the water spreads in time of flood.

"If the general slope descended by an alluvial stream is relatively steep, its course is relatively direct and the bends to right and left are of small angular amount. If the general slope is relatively gentle, the stream winds in an intricate manner; part of its course may be in directions opposite to the general cour.se, and some of its curves may swing through 1S0° or more. This distinction is embodied in the terms direct alluvial stream and meandering stream. The particular magnitude of general slope by which the two classes are separated is greater for small streams than for large. Because finene.ss is one of the conditions determining the general .slope of an alluvial plain, and becau.se the gentler sloi>es go with the finer alluvium, it is true in the main that meandering streams are associated with fine alluvium."

Conmienting on the curvature of a channel, which greatly compli- cates the transportation and deposition of debris by a stream, Gilbert says :

"In a straight channel the current is swifter near the middle than near the sides and is swifter above mid-depth than below. On arriving at a bend the whole stream resists change of course, but the resistance is more effective for the swifter parts of the stream than for the slower. The upper central part is deflected least and projects itself against the outer bank. In so doing it displaces the slow-flowing water previously near the i)ank, and that water descends obli(iuely. The descending water displacM's in turn the slow-flowing lower water, which is crowded towai;d the inner bank, while the water ireviously near that bank moves toward the middle as an upper layer. . One general result is a twisting movement, the ui)per parts of the current tending toward the outer bank and the lower toward the inner." Another result is that the swiftest current is no longer medial, l)Ut is near the outer or concave bank. Connected with these two is a gradation of velocities across the bottom, the greater velocities being near the outer bank. The bed velocities near the outer bank are not oidy m\ich grt-ater than those near the inner bank, but they are greater than any bed velocities in a relatively straight part of the stream. They have therefore greater capacity for traction, and by increasing the tractional load they erode until an e(]uilibrium is attained. On the other hand, the currents which, cro-ssing the bed obliquely, approach the inner bend are slackening currents, and they deposit what they can no longer carry.

T' The system of movements here described has been observed l)y many students of rivers. They were demonstrated by the aid of a model channel Ijy J. Thomson, in con- nection with an explanation which differs somewhat from that of the present text. See Roy. Sec. London Proc, pp. 5-8, 1876, and 35G-357, 1877; also Inst. Mech. Eng. Proc, pp. 456-460. 1879.

S(H-. II] (iKOLOCY OK I'LACKK DKI'OSITS -.1 KN K INS 191

"It rt'sills tliiit tin- scclinii on :i ciiivi' is :isviimit't ric, tlic 'rc'itost Ix-iii- iH'iir tli<- niil.T l);mk. As IIm- windiiiu stn-.-ini cli.-iiiios tlic direction of its ciirvnturf from oih" side to the oIIht. tiif twisliiiK system of current liliiments is reversed. :iiid with it tlie system of depth, Init tiie process of chiiUKe includes a jduisc with more tMiuuiile distrihut ion of velocities, und tiiis phase produces a slioal soparatinfj the two deeits. The shoal does not cross the cha!inel in a direction at rifjht angles to its sides liut is somewiiat ohli(pie in position, lending; to run from tiie inner bank of one curve to the inn<-r ItanU of the otiier. In meandering streams it is usually narrow and is .-ippropri.itely called a har. In direct alluvial str.-ams, where bends are apt to be separated by loiif;, nearly straif,'ht reaches, it is usually broad and may for ji distance occupy the entire width of thi channel."

Deposition

The nature of slreaiu or fluvial (l('i)osits aiid t.lieir detailed structure and texture is described in various text')ooUs, but not with sufficient detail to explain all the types of complicated features found in f,'ravel deposits, especially complex deposits such as those of a mountainous region like the Sierra Nevada.

Quoting- from Longwell, Knopf, and Flint '- on "fluvial deposition" : "The constructive process of fluvial deposition jcoes forward side by side with fluvial erosion. This is a result of the complexity and variability of the stream currents, which constantly drop some rock fragments to the bottom while they pick up others. When a stream is actively eroding its bed at a certain point, it is merely pickin;; up and carryinj; away more rock material than it is d<'positinf,' there, and when it is actively <lei)ositin>,' reverse is Koinj; on. Therefore, whereas fluvial erosion and deposition are processes iihysically o]>i)osed to each other, they can be separated in practice only by recognizinj; the preponderance of one over the other."

The arrangement of materials deposited in a delta, however, is well known, and gives a picture which is more or less duplicated whenever the current of a stream is checked by a body of standing water and the materials transported are permitted to drop. The term 'foreset beds' is applied to the deposition on the frontal slope- of the growing embank- ment. ' Bottomset beds ' are of finer grain and are formed by the particles carried out beyond the slope and deposited in deeper water. 'Topset beds' are composed of the materials laid down and spread out on top of the other materials by the fluctuating stream.

The material deposited by a stream is called alluvium and makes up fan, tloodplain, and delta deposits. The term 'fanglomerate' is used for the gravel materials of alluvial fans.

An alluvial fan is built up at the point of abrupt change in gradient of a loaded stream. A floodplain is a series of coalescing alluvial flats along a valley. A delta is the final deposit by a stream, unloaded as it enters a still body of water.

Overflow of a stream onto its floodplain will cause natural levees to be built up as low ridges bordering the channel. Lateral swinging of a stream causes cutting on the outer sides of the curves and depo- sition on the inside, which results in the widening of the valley. A mean- dering stream may develop to the point of straightening itself in places by the cutting off and silting up of the meanders, forming oxbow lakes as a result. A stream which forms a complex interlocking network on its floodplain typifies anastomotic drainage. An overloaded stream on a low gradient, becoming choked, and constantly obliged to cut new' channels, develops an intricate network on a floodplain ; the process is termed 'braiding.'

Longwell, Knopf, and Flint, op. cit., p. 44.

I'LACKH MININC KOH COIJ) IN CALIFORNIA [Bull.135

F=v ; tOj .. O. - T - H 1 L S U O P E

F O O

F p O T - M ' ', L S L O

Fig. 71. A, Diagram to show a meandering .stream with oxbow loops. Such a stream develops in a valley worn down to ba.se-level and not subject to extensive floods B, Diagram to show a subdividing or anastomosing stream m a valley sub- ject to floods; (tfter Johnson, U. S. Ceol. Survey 22d Ann. Kept., 100.

Sec. II] GEOLOGY OF PLACF.R DEPOSITS — JENKINS 193

If the stream is rejuveiiated and therefore cuts deeper, floodplain terraces or benches are formed. The benches nia.y, however, be cut and left in the bedrock and covei-ed ith only a fihn of j:ravel on the surface.

Streams composed entirely of tiiick mud, called 'mudflows,' are akin to landslides.''' Quotinj? from Longwell, Knopf, and Flint :

"Aiiothor norin.'il tli<)H<;h iiifroqiu'iitly operative proco.'.s in arid regions is the nnulflow. It occurs only where fine rock material becomes water-.soakecl on steep slopes after heavy rains, and moves downward as a slippery mass. ... It advances in waves, stopi)inj; when it hecoines too viscous to flow and damming the water behind it until it liquefies and again proceeds like an a<lvancing flow of lava. Mudflows can carry boulders many feet in diameter. Observers have seen these great rocks bobbing 'like corks in a surf.' Successive mudflows play a part in the building of fans."

The transporting: power of mudflows, their various peculiarities, and the resultant un.sorted deposits have many characteristics much like those of glacial deposits and have frequently deceived engineers.

The distingui-shing characters of glacial deposits are clearly sum- marized by Blackwelder, ' who has made a special study of them :

"The deposits left by glaciers should be distinguished from those made by streams, lakes and other agencies.

"The ice tongue of a glacier leaves only one type of deposit called till. It is wholly unstratified and its components are quite unsorted — a jumbled orderless mass of clay, sand, and boulders. Blocks three to five feet in diameter are common and those 2.j feet or more are not rare. In general, the size of such boulders depends upon the spacing of the joint-cracks in the rocks of the mountain sides. Usually till is an earthy mass well si)rinkled with stones and boulders but in some cases the boulders predominate. This is particularly true of the deposits of small glaciers which have done little more than sweep the coarse talus from the valley slopes. The stones in till may be of any shape from well-rounded to angular but many have the corners and edges rounded. It is usual to find some that have been bevelled by being rasped along the bottom of the glacier. Hard rocks may thus be well polished. Such stones, like the bedrock, are covered with scratches which are easily recognized.

"It is often difficult to identify till, especially if it has been much decayed or eroded or is poorly exposed. It may then be confused with other bouldery deposits which are unstratified. From volcanic mudflow deposits, .such as abound in the Miocene beds on the Sierra Nevada Hanks, till may often be distinguished by its containing large quantities of nonvolcanic rocks. Even this criterion fails where glaciers occupied volcanic mountains such as Mts. Shasta and Rainier. Ordinary mudflow deposits are seldom as thick as glacial moraines and are generally inter- bedded with typical stream gravel and sand, as in the alluvial fans of the arid regions. Unless the surface topography is still preserved or unless one finds plenty of scratched stones, it may be almost impo.ssible to distinguish till from landslide dumps. In many cases no one type of evidence can be relied on, but one must study all the facts and weigh the importance of each.

"The rivers which issue from glaciers deposit coarse gravel, then fine gravel, and finally sand as the current weakens near the edge of the mountains. These three grades of detritus are more or less interbedded, because variations in the river's power occur from time to time at a given place. Like river deposits in general, those of glacial streams are distinctly stratified, though usually cross-bedded. They are fairly well .sorted into separate layers of sand and gravel of various sizes. The pebbles are normally well rounded and very rarely either faceted or scratched. Angular stones are rare. Although small boulders are carried by ice cakes and become stranded in the glacial river gravel, large boulders are generally absent.

"Blackwelder, Eliot, Landslide family and its relations (abstract): Pan-Am. Geologist, vol. 54, p. 73, 1930.

Finch, R. H., Mud flow eruption of Lassen volcano: The Volcano Letter, no. 266, pp. 1-4, 1930.

Longwell, Knopf, and Flint, op. cit., pp. 77-78.

Blackwelder, EVrot, Glacial and associated stream deposits of the Sierra Nevada : California Div. Mines, Mining in California, State Mineralogist's Rept. 28, pp. 306-308,

104 l'LA( i:iv' .MINI.\(i I'OK (lOLl) I.V C'ALIFOKNIA [. 1:)")

'I'.. .Iislii.;;ni-li Ihr .|.|M.sils (.1" :i ;;l;M-ial In. in .-i ii..ii'l;ici:il lix.T is .lifliciilt

iiiiil iiriiii iin|M>>.sili|r. iiiilfss <;iii tr;ni' llic ;;r:n(l lrir:iccs into iictuiil connection

Willi ;i ul:i.-i:ii I .lin.' ..r ,-,in work nnl in <l.i;iil Ihr phx si,,;;, ;i,,liir hisluiy ,,f tlir

liistlirl.

'rill- (Irposils ni:i<l.' in uhii-i.il lakes aie lallicr disi incti\ o. On lln- liottoin

of tin- lakr, clay ami sill air laid duwii very cNciily in thin si Is which arc coni-

inonly Itainlcd as s.-ni lalr in ci-.,ss- iuii. This is dni> to llic fact llial the layer drposiled in winter is finer and riarker in color than the one laifl down dnrin;; the Miniiner niellin' season. Inlike most laki- ileposits the ;,'lacial lake <-lays coinnionly

contain scattered pel.l.les and even small l.oiilders which have I n dropped from

cakes of ice lloaliii;: over the lake. These laininaled clays may he associatc-d with heds of peat or chalky or dialoinaceoiis earth formed l>y or!,'aiiisms that inhabited the i-learer parts of the lake. Si reams entering,' tin; lake form advanciii}; deltas compo.sed of ui-ivel and sand in which liie rat ificatioii is characteristic of deltas in ;;eneral. Ill |iianlily llie .hlia dcp,,sil-, ,.licn e.\c4'ed I h<" other lake <leposils fin-atly, for I In- glacial rivers carr\ lar;;e ,|iiaiil it ics of coarsi' delriln- all ..f which lod-es in the d.-ltas rather than upon the 11 - of the lak.'.

Other deposits that may he forimwl in L;laii.ii valleys, such as landslides, tains, and alliivi:il fans, lu'cd ii.,t descril.cl sp.'cific.illv . 'I'hey ,ire l..cal .iikI cifr.illy well known."

Tlie (l('('i)('Miii<i of canyons and llic dtposition of iiavels by oiitwasli si reams wliicli issnc from the snoiils of glaciers form a very important chapter in the r(>hl)in,i|- and destrnetion of earlier (jld-bearinji' jiravels. Much the material carried by JMeistocene glacial outwash streams (,f the Sici-ia Xcvada vas diimi)e(l at the foot of the western slope of the i-anjic at llic point where ihe major rivers (Milcr the CJreat Valley. The extensive old-drcdiiiiij' oi-onnd of California 1o a lar<>-e extent owes its existence to these streams.

So far as the ))rocesses involved in streatn action are concerned, can l)e oained by the detailed study of ancient ;lacial stream channels fonnd throiifilioiit the world, especially in'its northern belt. The mass of literature published on this subject should contribute ofcatly 1o the hiiijdiiit:' up of a sysi(Miialic knowledge of stream liabil. Physiographic Terms Relating to Streams

'J'lie mere dednition of some of the tei-ms used in stream ])hysi- o<ii-aphy o-ives a dii-ect insioht into the science."''

'Cycle of erosiou' includes the sei-ies of ciianp:es from the initial cuttino' of a surface to the final reduction of a rejyiou to a baselevel. The surface of a rejiion reduced to fairly low relief, but still undulat- in<r. is called a '])eueplaiir (also spelled i)eneplane).. It is a si<:nificant fact that the Sierra re;:ion in early Tertiary time was aj)pi'oachin<i- the pciu'plain stajic of erosion, when the area was covered with lava to form a more lU'arly jilain-liUe surface, and later uj)lifted. The uplift caused deeji dissection l)y streams.

Sta<i:es of stream develoi)meiit, from <iulle>s to eom]>letely worn- down plains, consist of youth, maturity, and old ape, with continuous 1 ransil ioiuil sta<,''es between. The early stages repres(Mit very rapid jii-owth, which slows down liiadiuilly until at old niic the chanjcs may be extremely slow.

The reiH'sis or orioin (,f the stream takes into consiileration the initial .surface over which the sti'cam fii'st flowed. Sevei-al tei-ms are used by seolo<i:ists in relation to this sub.)ect. (Consequent streams are those whose positions were determiiu'd by the initial slopes of the land surface. Subsecpient streams are those which are established by orowing headward along; belts of weak rocks.

'"Johnson, DouKlas, Streams niul their siKHiticance : Jour, fleologv, \ol. 40, n. 482, 1S32.

Sec. II] cKor.odV OK i'i;.\(i;i; i)i;i'()si'rs .jiakins 305

WlioiT the uiul(M-lyiii<x stniclurcs of llic recks have affected tlie (lii-oetioii of tlie stream and its vjdley, llie stream is siiid to luive struct m';d eonti-ol. The terms faidt, joint, strike, anticlinal, sviiclinal, ;ind nioiio- elinal are prefixed to the -word 'valley'; thus, fault-valley, st i-ikc-vaHcy, etc. It is esj)eeially si'nificant that tlie richest i'ol(l-beai'in- channels have structural control — the streams oi-iiinaily ran on <nid aloii' min- ei'alized zones in bedrock.

Streams may start theii- coui'ses over one sort of <:eol()ic;d foniui- tiou, but as time pro'resses they ma\' cut thi-ouh it and be let down on a lower and entii'ely (litferent type of structnire; such streams are s;iid to lie 'supei-imposed ' (or simply superposed) on the underl>in' rock struc- ture. When a certain stream ])attei-n, originally devcloix'd because of pi-evious toporaphif or struct iiral conditions, is retained even ;if1ei- those conditions are removed, the sti-eani is said to Iwive inliei-ited its ix'cnlinr features from much earlier jieriods of its life.

Streams may be intermittent or iiermanent. Depression of topoj- raphy along a coast may cause the sea to invade the valleys, and the sti'eams are drowned. T'jn-ise nlonu' the coast may leave han<ii:ing valleys. Tributaries to a main stream -which has been much fastei--cutting may also be left 'hanpinfr'; as, foi- example, in Yosemite Vall(\v where the side streams reach the Merced Kivei- by way of beautifid watei-falls.

The lonjiitudinal profile of a stream is taken from its source to its mouth, -while its gradient represents its inclination at some particular part of its course. Ti-ibutaries are said to be accordant Avhen at about the same level as their main stream. A stream is sa <ii-ade when rate of degradation and rate of aggradation equal.

A stream which is able to maintain its course, even when a segment of the earth is gradually raised atlnvart that course, is called an ante- cedent stream. If, however, the uprise of the mountain causes the flow of the streams to be accelerated down its slope, so that they cut deeper gorges, they are said to be re.iuvenated. Even stream meanders, developed on a plain, may be entrenched or incised deeply, to form a winding canyon by elevation of the plain.

Rejuvenation may be efTected in other ways than mountain-making. Change of climate may make a decided change in stream cutting. Stream piracy is another im])()rtant cause. This consists of the cajiture of one stream by another. The second lies at a lower elevation ; its head cuts back until the first is tapped, oi- beheaded. Then the water frf)m the first stream, from that point ui)ward, is caused to flow into the cap- turing sti-eam. In this maimer the flow in the first is accelerated often to such an extent that a new gorge niay be formed. Whole stream systems may thus be readjusted and repeatedly go through new life cycles. Piracy and stream a<ljustment were a])parently very active in tlie Sieri-a Nevada during Tertiary time; this ]irocess partly accounts for many of the deep accumulations there of Tertiary gravel.

The pattern of an individual stream, or of the -whole or any ])art of its system, develops in its own peculiar way bcn-ause of c(M*tain con- trolling geological, topographical, and climatic features. The iattern, therefore, is a chJiracter significant enough to bear special study and to support many new descriptive terms. It is now best studied by means of aerial photographs, though detailed t()pogra])liic and geologic maps once presented the only bases of accurate expression.

thev

ent

er

id to

be

at

are

abo

ut

Placer Mining For Gold In California

[Bull. 185

Fig. 72. Diagrams to illustrate three successive stages in stream piracy. Tiie stream cutting back at the lower elevation beheai/s and captures the stream flow- ing at a higher level. After BhickucJdrr and Bmroiis, Avierican Book Co.

Sec. II] GEOLOGY OF I'LAfEK DEPOSITS — JENKIXS 197

Manj' clues as to the geologic structure and history of the underlyin*'- region are gained by the study of stream pattern, from either an intensive or regional point of view. In the northern Sierra Nevada, the stream pattern developed jirior to volcanic activity was structually controlled by bedi-ock; but during the hiter period of vok-anism it sufi'ered cliange by that widespread activity. Tlie nuijor streams subsequent to volcanism followed the slope of tlie lava-covered, tilted, and uplifted fault-block- range.

An instructive outline of the subject of stream pattern is given by Zernitz.'" who desci-ibes and illustrates by many actual examples su<-h patterns as follows: dendritie. trellis, i-ectangular. ainiular, radial, and parallel. He states that :

"Tlio pjifti'i-iis wliirli strciiins form .-irc (Ictcnniiicd l)y iiipquiilitics of surf:icf slop*' and inoqn.-ilitifs of rock rosistiiiuH-. This Ijciu- true, ir is ovidcnt th:U draiii.ifif patterns may rcflcot orifiinal slope and oriu.ina] strneture or the successive episod<'s ly which the surface has been modified, inclndiiij: iiiilift. depression, tiltinj;, -warpinir. folding. fauUinj;. and jointinjj. as well as deposition by the sea. glaciers, volcanoes, winds, and rivers. A sinjrle draina.'e pattei-n may be the result of one or of several of the.se factors."

The fact that lakes fill dein-essions, basins, and valleys along stream courses, and that their deposits are intimately associated with those of streams, makes their study interrelated with that of stream channels. The so-called 'pipe-clay' deposits, which nearly always immediately overlie the gold-bearing gravels, represent beds of silt and finely divided volcanic ash, which have .settled in lakes and formed a series of thin layers. They often contain impressions of leaves, showing the character of the forests that grew in that early period. This feature indicates that before the volcanic flows came to cover them up, the stream valleys had been transfornuHl into lakes, into which the volcanic ash settled.

In general, a lake is not as long-lived as a stream. Streams tend to destroy lakes, either by gradually filling their basins with detritus or by cutting down their outlets to a point where their basins may be drained. Sometimes, however, lakes persist long enough so that the area whose drainage they receive is worn down to a local and temporary baselevel. Lakes are formed in a uumber of ways: by landslides across stream courses; by lava floAvs which dam up the drainage ; by the down-faulting of segments of the earth which are then filled with water; by glacial action, either by scooping out rock basins or by danuuiug with till ; by peculiar action of rivers themselves, such as silting otf oxbow loops in a meandering course. An excellent paper written by the late Dr. W. ]\I. Davis has recently been published, which not only discusses the present lakes of California.' Imt the origin of lakes in general.

Desert Processes

In the desert, the processes of erosion and of stream action differ very much from those in more humid areas. Only quite recently have the geologic processes in the desert been given much consideration ; so also has much serious thought f)idy lately turned toward the possible development of desert placei-s on a larger scale than mere 'dry wash- ing.' The fact that adequate supplies of water may iLsually be derived

"Zernitz, Kniile, DrainaKe patttins .iiid tbcii- sif,'i!ificanoe : Jour. Ceolngj-, vol. 1.'., p. 498. 1932.

™ Davis, William Morris. The lakes of ( alif..rnla : California .lour. :\rines and Geology, vol. 29, pp. 175-230. 1933.

PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Fig. 73. A, An example of dendritic drainage pattern, which develops where the underlying rocks lie in a horizontal iiosition and offer uniform resistance to erosion. After Zernitz, Jour. Geology, 1932. B, An example of trellis drainage pattern which develops in folded rocks differing in degrees of resistance to erosion. The stream courses are therefore structurally controlled. After Zernitz, Jour. Geology, 1932.

e It

Fig. 74. Map of southeastern margin of San Joaquin Valley showing funs built by streams which disappear after leaving their mountain canyons. The coalescing alluvial fans form in this manner an extensive bajada. After Slichter, U. S. Geol. Survey Water-Supply Paper 67, 1902.

Sec. TT]

(iKOIiOdV Ol' I'LACKU I)i:i'()Sl'

Fig. 75. A, Block diagram illustrating Cretaceous Sierra Nevada topography. The upturned edges of bedrock controlled the drainage pattern, wliich was later inherited by streams of the early Eocene period. After Matthes, U. .S. Geol. Survey, Prof. Paper 160, 1930. B, Block diagram to show the tilting of the Sierra Nevada and its effect on stream cutting.' Erosion, prior to the tilting, planed down the sur- face and exposed the granite, leaving only occasional fragments of the intruded metamorphic rock bodies as roof pendants. The streams, at the point where they leave their mountain canyons and enter the Great Valley, form alluvial fans. After Matthes, U. S. Geol. Survey, Prof. Paper 160, I'J.SO.

Fig. 76. Diagrammatic geologic cross-section of Table Mountain in the vicinity of Columbia, Tuolumne County. The following principal geologic events affecting the ancient channels of the district are graphically illustrated : (1) An early Tertiary surface, developed on bedrock over which flowed the old river system of the Plum- bia basin. (2) This surface, including its rich gold-bearing gravels, was later covered with lake sediments ('pipe-clay') consisting of fine silty volcanic ash. (3) Ande- site 'cobble-wash' then covered the entire country. (4) A canyon was cut in this andesite mudflow. (5) A basic lava (latite) flowed down this canyon as a molten stream. (6) After this lava cooled and hardened, it became the bed of another river which deposited some gold-bearing gravels on its surface, washed from the surround- ing eroded region. (7) Continued erosion during tlie Pleistocene resulted in the wash- ing away of the less resistamt volcanic materials, leaving the very resistant latite standing as Table Mountain. Furthermore, the earlier prevolcanic bedrock surface was uncovered, or resurrected, exposing the gold-bearing gravels originally deposited in the Columbia channel system. (8) Quaternary erosion has cut canyons of great depth, far below the level of the former Tertiary surfaces.

200 PLACER MINIXG FOR GOLD IX CALIFORNIA [Bull. 135

from uiulery:rc)uiul sources in the desert, and the fact that tliese sources may be found throup-h {reolofrical investigation and peophysieal survey- ing;, are prradually being: accepted.

Tlie most sijrnificant results of recent desert-process studies are sunnnarized by lilackAvehler as he describes the five distinct types of desert phi ins:

1. rfdiinfiits (iiioIiuliiiK tlmse only thinly venoi-rt'd with iilluvial fans), which ri'i'iosont the desert slope, cut in bedrock, in contrast to the built-up thick alluvial fans or bajadas.

"reilinients are essentially cuniiinimd ;:ra(le(l flondplains excavated by ephemeral stn-anis ii,,. pediment, not (lie ba.jada, is the normal and inevitable form (levelo|)ed in the arid recions under stable conditions."

2. Bajadas'*' (compounded alluvial fan.s), which are built iip largely as a result of disturbed or interrupted development of fjraded .slopes. The upward movement of a fault block causes renewed erosional activity, and thick gravel deposits are formed by the conse(iuent titrrents and mudflows when thoy are rele.i.sed from their canyons and enter a region of lesser gradient.

3. Dried-tii lake bottoms of the desert, or playjis, whose conditions indicate that once more i)ermaMeMt lakes tilled the flats and were fed by streams that are now nonexistent.

4. Dip sloi)es, which are broad planes develoiied on a denuded, hard, flat-lying or gently tilted rock layer.

5. River floodplains, which are abnormal desert features, but which were apparently more widespread at an earlier time, when precipitation in a given region was much greater than it is today.

These earlier plains and stream courses have been covered b}- the bajadas of today, so that the older channels have become buried in the true sense of the word. Some of them may represent a large potential placer reserve, but they have not yet been well investigrated.

Need for Establishment of Working Criteria

From the study of the complicated life history and habit of streams and the jiroco.sses involved in their development, a series of working criteria should be developed by the exploration geologist for inter- preting the conditions found in the deposits of all streams, including those of Tertiary age in the Sierra Nevada. There is no text available that completely covers all phases of streams — their life history, habits, deposits, etc., especially as this study is related to ])lacers, but the subject offers an interesting field of research which would have a very broad economic application.

Geologic Conditions in the Gold Provinces of California In the Sierra Nevada and Klamath Mountains of California gold- bearing quartz veins are generally found in metamorphic rocks not more than a few miles, at the most, from int)-usive bodies of granitic rocks. The age of the metamorphics, which are made up of slates, schists, limestones, and meta-igneous bodies, is earlier than Cretaceous, namely pre-Paleozoic, Paleozoic, Triassic, and Jurassic. The time of intrusion of the granitic masses was late Jurassic.

The quartz veins were formed shortly after the igneous intrusion, during the last stages of the Jurassic. It w(mld seem that the meta- morphic rock masses were uplifted and intruded by molten magmas which then cooled and contracted, causing the surrounding and over-

™ niackweUler, Kliot, Desert plains : Journ. Ceolotry, vol. Sit, pp. l.TS-l 40, ]!t.31.

Tlie luiMie h(i)uda placer as adopted somewhat erroneously by Webber and previ- ously descrilied in this paper, refers more to single alluvial fans rather than to these compound forms.

See. II] GEOLOGY OF PLACER DEPOSITS — JEXKIXS 201

lying roof-rocks to craek along many planes of -weakness and to form thousands of fissures. Into these openings the residual gaseous solu- tions, released from the crystallizing granites and composed largely of silica, were injected These, after solidifying, were crushed again, and solutions containing gold entered the complex mineralized zones, enrich- ing especially the cross-fi-actnres where openings were most abundaht.

The gold-bearing veins thus formed deep beneath the surface of the earth, had then to be brought to the light of day by the erosion and removal of the covering layer of rocks, nearly two miles in depth. This gigantic work was accomplished during tlip Cretaceous period, and as a result thousands of layers of shales, sandstones, and conglomerates several miles in stratigraphic thickness were laid down in an adjoining marine basin. Some of these beds — especially the last ones to be deposited — are gold-bearing, showing that the last part of the Cretaceous erosion finally reached the hidden veins.

That part of the geologic history, however, which was most important so far as the making of rich placer deposits is concerned, was the Eocene period. The deep erosion which took place during the Cretaceous had worn the surface down to such an extent that the metamorphic rocks with their mineralized zones had been reached, so that the streams of the Eocene ran along and through them.

Structural control of the drainage, fully developed during the Cretaceous, was thus iidierited by the Eocene streams. Ridges and valleys followed the north-south trending beds of hard and soft rock. The subtropical climate of the early Eocene together with other condi- tions particularly favorable to rock disintegration, such as a more pro- longed time of stability in the earth's crust, made it possible for the gold in the surface rocks to be released from its matrix.

Then came the inception of the Tertiary Sierran uplift, which rejuvenated stream flow, causing the released gold in the disintegrated veins to be washed into the river channels, resulting in very rich con- centrations. The streams were loaded with fine quartz sand and pebbles, together with clays derived from the decomposed feldspathic parts of the rocks. The finer particles were washed to the sea, and as a result the Eocene (lone formation) today contains large deposits of com- mercial clay interbedded with quartz sands.

The westward tilting and resulting acceleration of stream flow interrupted the north-south drainage system inherited from the Creta- ceous period. The readjustment of the streams resulted in their general direction of flow being finally changed from north and south trends to a westerly course, somcAvhat as it is today. The longest of these known streams even headed far to the east into what is now Nevada.

Hardly had the Eocene come to a close when much rhyolite ash, thrown into the air from volcanoes, settled over the region. By Oligo- cene time, rhyolite ash had covered much of the northern Sierra Nevada, damming rivers and forming lakes, the bottom sediments of which are now represented by thinly layered pipe-clay immediately overlying the richer gold-bearing gravel. The newly developed rivers, flowing directly down the western-tilted slope of the Sierra, over a volcanic cover, as consequent drainage, were repeatedly interrupted by continued ejections of lava and a further tilting of the region. Not until the late Pliocene or early Pleistocene diet the constant out-pouring of lava cease. Then,

'J()2

PLACER MININ'O FOR OOLD IX CALIFORNIA [Bull. 13.'

n-

Fig. 77. Aerial map (for explanation, .see fig. 7 8 caption). Photo by courtesy of Fairchild Aerial Sirveys. Inc.

Sec. II]

Geology Of Placer Deposits — Jenkins

Bed A'ocA-

Fig. 78. Index sketch (reduced) of the same area shown in figure 77. Explana- tion of figiire 77 : Mosaic made up of many overlapping vertical photographs taken from an airplane, elevation 10,000 feet : area 6 J by 4 miles, between Jamestown and Angels Camp on the Mother Lode (see fig. 78). The Stanislaus River winds through the upper half of the picture ; in the lower, the Table Mountain latite flow, which occupies a late Tertiary canyon cut in andesite 'cobblewash', stands oi t in bold relief. The softer andesite rocks and the underlying 'pipe-clay' cut by this canyon have been stripped away by Pleistocene erosion, save for two or three small patches remaining in protecting curves of the harder lava flow. The surrounding country lies lower than Table Moun- tain in elevation, and is worn in bed-rock. The prevolcanic gold-bearing channels are represented only as gravel-filled fragments, which, however, show their northward trend, parallel to the strike of bedrock and the Mother Lode. These remnants can be recognized in the pictures only after field examination. One such mined-out channel passes under Table Mountain at right angles to it, near its central position in the picture. It was here that the Humbug drift mine on the south met the New York tunnel on the north, resulting in an underground fight, and later litigation.

Placer Mining For Gold In California

[Bull. 135

iih. . .JUy

i

iSittR'

fr--

mm

mmM

Fig. 79. Surface of the resistant Table Mountain Uiliic la\u llow which once filled a canyon cut by a river in andesite 'cobble-wash'. Later the latite surface served as a stream bed: now it is the flat mountain top in Tuolumne and Calavtras Counties referred to in the writingrs of Mark Twain and Bret Harte. Cut by courtesy of Engineering and Mining Journal.

by a series of violent earth movements, the Sierra Nevada broke away from the region to the east along huge fault-scarp.s, which are formed at the foot of the present steep eastern slope, where displacements are now measured in thousands of feet. Within the Sierran slope, smaller adjustment faults also broke the continuity of the older buried Tertiary stream grades. Some of the ancient streams, the courses of which headed farther to the east, were virtually 'cliopped' into many pieces ; some were elevated and others depressed, and many were warped to various peculiar positions. Undoubtedly there are some segments of these old channels which now lie deeply buried beneath great tliicknesses of alluvium in down-dropped fault-blocks east of tlie Sierran escarpment.

In the Great Basin and the Mojave Desert region of California and Nevada are remnants of Tertiary stream deposits, interbedded with or lying beneath lavas, all of which have suffered nnich by faulting and warping.

In these regions, however, the most important period of placer formation was in the early Pleistocene, rather than in the Tertiary, Two types of lode gold supplied the sources. One type was formed in much the same manner as the Sierra Nevada lodes. The other consisted of mineralized zones in rhyolite of early and middle Tertiary time. In the Pleistocene there were normal streams flowing through the desert, fed by melting glaciers of the higher mountains. Placers that were formed by these Pleistocene streams have since been largely covered by desert alluvial fans. Some have been elevated and are cut by more

Soc. ir

fiKOIiCKiY OF PLACER DEPOSITS — JENKINS

Fir.. SO, Ideal cross-sr,-

liun of a

ri\rr in tl

H Sierra Nevada

the bed of wliieh

lias suffered down-faultiiipr on

tlic ui.st

ream side

causing gravels,

sand, and silt to

ai'cumulate in the pocket thus

formed.

recent streams, -when present in this arid region, so that recent concen- trations from older river gravels provide one source for the desert dry placer.

In the Klamath Mountains, though the early geologic history was much like that of the Sierra Nevada, there were no lavas to fill the valleys in which the stream gravels were deposited. Uplifts, accompanied by renewed stream-cutting, caused terraces to be left on the valley sides, where the rich gravels have given up their gold to hydraulic mining. Some of the finer gold particles were washed by the rivers to the sea and have formed deposits known as beach placers along the northern shore of California.

Down-faulting of various degrees of magnitude in places caused accumulations of gravels to form, especially on the down-throw sides of faults. A number of such faults are located in both the Sierra Nevada and Klamath Mountains, and may hold a reserve of gold not yet entirely recovered. In the Sierra most of these minor displacements show that the east side of the fault-plane has been dropped down, so that where faults cross westward flowing rivers, accumulations of gravels have taken place in pockets thus formed, east of the fault-plane and upstream.

The whole Pleistocene period was one of great events for California. The eastern side of the Sierra Nevada was raised to very lofty heights. The westward-flowing streams, as a consequence, were so greatly accel- erated that they cut deep and rugged canyons. The uprise, accompanied by faulting, caused such violent earthquakes that enormoiLs masses of rock were shaken from the mountain sides, in many places to form local lakes which were later to be drained and destroyed by active erosion. Glaciers developed in the higher mountains and crept down the canyons, carving them wider and leaving them U-shaped in form. Their melting supplied much w'ater to the streams. Some local volcanic cones were built up here and there near or over the fault planes.

The Tertiary stream gravels, which had long been buried deeply beneath lavas, were exposed by the Pleistocene canyon-cutting rivers. From the dissected portions of the old channels, gold was removed and washed into the newer streams, which concentrated it on their bedrock riffles. The remaining portions of the Tertiary deposits were left with their stubs exposed high up on the intervening ridges. In places, erosion merely stripped the covering of volcanic tuffs, sands, and gravels from the bedrock, leaving the channel with its rich gold deposits laid practically bare for the lucky early- miner to win. Some of the finer particles of gold were swept clear out to the Great Valley where

Q)

206 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

they were dropped on the edje of the i)laiii. These areas ai-e now the dredge grounds.

The general western tilt of tlie Sierra Nevada has been found to eontinue along the same slope (about two degrees) far beneath the alluvium and sediments of tiie Great Valley. Areas dredged for gold values in the gravels thrown down by tlie great canyon-cutting rivers of the range lie along the extreme western margin of the foothills near the place where bedrock passes beneath the alluvium, and aligned in a direction N. 20° W. The gravels dredged do not lie directly on bedrock but on tuffaceous clay layers, spread out above the detritus-covered down-warped iSierran surface. Beneath the 'false-bedrock' and cut in the true bedrock surface is a stream pattern with gold-bearing gravel-filled channels, now reached only in one or two places. This buried channel system undoubtedly holds in reserve a great wealth for future improved exploration and development. Excessive underground water is ahvays encountered in these mines which are located beneath the level of the alluvial plain.

The great differences between the geology of the Coast Ranges and that of the Sierra and Klamath regions are fundamental in that the western area served frequently as a basin for deposition during the Tertiary and Cretaceous, while the latter represented land areas through- cut that time. The Coast Ranges together with the Great Valley now contain enormous accumulations of marine Tertiary and Cretaceous sediments, while the Sierra Nevada and Klamath IMountains are not so covered. Cretaceous and Tertiary streams coursing down the moun- tain flanks brought gravel, sands, and clays into a marginal sea.

The very fact that streams are conveyors of materials, in contrast to the basins of deposition toward which they accounts for the very different geologic conditions on the two sides of the Great Valley. Certain geologic time divisions of the Cretaceous and Tertiary of the Coast Ranges are represented by strata measured in ma)iy thousands of feet, while in the Sierra mere films of Tertiary gravels, or deposits of no greater thickness than a few hundred feet, trapped by volcanic coverings, represent some of these same later periods. Particles of gold, recurrently washed from the mineralized rocks of the mountain range, were dropped, reason of their high specific gravity, and retained in the bedrock riffles of both the ancient and modern streams, while the lighter detritus was carried to the broad sea basins to form strata cover- ing hundreds of square miles.

Conclusion

The depletion of the more accessible and more easily discovered gold i)lacers, followed by lo.sses due to poorly directed exploration, calls for a more effective technicjue to bring further success to placer mining. The techni(iue is available; the next thing to do is to apply it.

First, there is aerial photograph}' which may speedily and accu- rately give a wealth of valuable information as regards geology, and in addition, the finest sort of a map showing surface features in greatest detail.

Second, there is geophysical surveying which, when coordinated with geology, may greatly aid underground prospecting in making new discoveries and in reducing its cost by more intelligently directing its course of action.

S(V. 11] Geology Of I'Lackh Deposits — Jenkins 207

Tliird, pli3-.sioyTai)liie eolojy, advanced to a more systematic science than ever before, may be nsed in unravelling the history of the ancient streams and their corresi)oiuling topography. Contouring the predava surface is found to be an excellent method of showing graphic- ally this ancient topography, and especially the old valleys in which la\' the early gold-bearing streams.

Fourth, a better understanding of desert processes in general and desert placers in particular should help to develop a gold reserve which has so far not received the attention it deserves.

PMfth, the technique recently developed in the examination of stratified sediments, their structure, texture, mineral-grain composition, etc., may be aptly applied to placers, to aid in tracing out their origin and the cour.ses of the older drainage systems noAV extinct.

In taking stock of the possible reserves of placer gold in Cali- fornia, several sources would seem worth investigating. All of these require detailed exploration prior to any attempt at mining. For the most part, these reserves are buried or concealed in such a way that they have either been overlooked or considered too remote or too much of a speculation for a mining venture. Such factors as involved water-rights, litigation, difficulty in gaining title, laws unfavorably atfecting hydraulic mining, lack of sufficient capital, and many other stumbling blocks now prevent good placer ground from being worked.

The possible reserves discussed in this report may be summarized as follows :

Pleistocene and Recent Placers

1. Deep river gravel deposits, over which the present larger rivers are now flowing. Recent and Pleistocene faulting caused gravel to be accumulated on the down-throw side of faults, while the rivers have (continued to flow over the gravels without washing them completely out.

2. Pleistocene stream placers, buried beneath alluvial fans of the Ch-eat Basin and Mojave Desert.

3. Recent ephemeral stream deposits and alluvial fans or 'bajada placers' of the Great Basin and Mojave Desert regions.

4. Marine or beach placers along the coast, for the most part located in northern California.

5. Isolated high terraces or bench gravels, such as those which occur in the Klamath Mountains.

Tertiary Stream Placers

6. Gold-bearing channels cut in bedrock which lie beneath the false bedrock layers of the dredged areas along the western foot of the Sierra Nevada.

7. Buried Tertiary channels and associated covered benches located in the well-known gold-bearing districts of the state. Large areas still lie buried and unexplored in some of the older mining districts.

8. Buried Tertiary channels and benches in the lava-covered dis- trict which lies between the Sierra Nevada and Klamath Mountains. ]\Iost of this area is probably too deeply covered to be reached by mining, but the southern marginal area may have some po.ssibilities.

9. Tertiary channels of the Great Basin and Mojave Desert areas, interbedded with volcanic rocks or lying beneath them.

208 PLACKH MINING FOR HOLD IN CALIFORNIA [BuU. 135

10. Tertiary iiiai-iiic jjIjuhms. l'inely divided jrold partic-les in the Joiie formation at tlio point wlicrc flie i-oiTcspojKliii'j Eocene streams entered the lone sea.

Cretaceous Marine Placers

11. Ci-etac-eous marine placers, lar'oly in the Cliieo conglomerate (ri)per Cretaceous) beds of northern California. The Lower C'reta- ceous beds are also reported to contain some <iold-bearin<r layers.

Largest Reserve

Tiie largest of these possible reserves probably lie in the remain- ing bnried Tertiary stream placers of tlie northern Sierra Nevada.

Bibliography of California Placers and Related Geological Subjects

Allen, Victor — The lone formation of California : Univ. Gal. Pub., Bull. Dept. Geol. Sci.,

Vol. IS, l'J2<J, pp. :!47-44,S Ailing, Mark N. — Ancient auriferou.s gravel channels of Sierra County, California : Amer. Inst. Min. Eng., Bull. 91, 1'J14, pp. 1709-1728 ; Trans. 49, 1915, pp. 238-257.

Ancient river-bed deposits in California: Pacific Min. News, Eng. & Min. Jour. I'ress, vol. 1, 1922, pp. 134-140, 161-106.

Geologic chart appertaining to the ancient river beds of California: Cal. State Min. Bur. Bull. 92, 1923, plate in pocket. Anderson, Chas. A. — The Tuscan formation of Northern California with a discussion concerning the origin of volcanic breccias: Univ. Cal. Publ., Bull. Dept. Geol. Sci., vol. 23, 1!I33, jjp. 21.")-27G. Anderson, Frank Marion — The physiographic features of the Klamath Mountains: Jour. Geol., vol. 10, 1902, pp. 144-159.

Pliysiograpliy and geology of the Siskiyou Range: (Abstract) Jour. Geol.. vol. 11, 1903, p. 100.

Jurassic and Cretaceous divisions in the Knoxville-Shasta succession of California: State Mineralogist's Rpt., XXVIII, 1932 (auriferous conglomerates), p. 326. Anonymous — Mastodon tooth in Amador County: Amer. Jour. Sci., (2), vol. 34, 1862, pp. 135-140.

A great gravel mining enterprise: Min. & Sci. Press, vol. 30, 1875, p. 70.

The Inter-Yubas ridge: Min. & Sci. Press, vol. 32, 1876, p. 312.

Placer Countv Minea : Min. & Sci. Pre.ss, vol. 33, 1870, pp. 33, 42, 65, 74.

The mining intere.sts of 1S70 : Min. & Sci. Press, vol. 34, 1877 (hydraulic mining), p. 41.

Theory of auriferous gravel channels : Min. & Sci. Press, vol. 41, ISSO, p. 226.

Spring Vallev mine: Min. & Sci. Press, vol. 42, 1881, pp. 441, 452.

Pocket mining and nuggets: JNIin. & Sci. Press, vol. 44, 1882, p. 190.

Dredging for gold: Min. & Sci. Press, vol. 45, 1882, p. 24.

Gravel: .Min. & Sci. Press, vol. 45, 1882, p. 328.

Measurements of auriferous earth : Min. & Sci. Press, vol. 45, 1882, p. 328.

The discovery of gold in California: Min. & Sci. Press, vol. 50, 1885, p. 37.

Auriferous gravel in Placer County: Min. & Sci. Press, vol. 51, 1885, p. 165.

New placer diggings: Min. & Sci. Press, vol. 55, 1SS7, p. 228.

River svstem of ralifornia : Min. & Sci. Press, vol. 55, 1S.S7, p. 228.

Buried trees in gravel mines: Min. & Sci. Press, vol. 02, 1891, p. 339.

Geology of Placer, El Dorado, and Amador Counties : Min. & Sci. Press, vol. 70. 1S95, pp. 308-310.

California's supposed great rivers of ancient times : Min. & Sci. Press, vol. 77, 1898, p. 401.

Prehistoric rivers of California: Min. & Sci. Press, vol. 79, 1899, p.' 544.

(1.1 channel jjlacers : Min. & Sci. Press, vol. 82, 1901, i)p. 175-176.

Cold (Ir.-.lging in California: Min. & Sci. Press, vol. 91, 1905, pp. 125-126, 141-142, 100-161, 178-179.

Hydraulic Mining in Humboldt County, California : Eng. & Min. Jour., vol. 79,

1905, p. 30

draulicking in Trinity County, California: Min. & Sci. Press, vol. 101,

1910, p. 143.

Hvdraulicklng at La Grange Mine, Trinity County : Eng. & Min. Jour., vol. 95, 1913, pi}. 1005-1007.

Map of black .sand deposits: Min. & Sci. Press, vol. 118, 1919, p. 264.

Uniciue placer development. River Placers, Ltd., engaged in unusual project

on Middle Fork of the Yuba River: Min. Jour. (Ariz.), vol. 14. no. 23. 1931, p. 4.

Auburv, I.rf'wis E. — (Jold dredging in California: (Introductory) Calif. State Min. Bur.

Bull. .".7, 1910, pp. xiii-xiv. Averill, ('has. \'olnev — Preliniinarv report on economic geology of the Shasta quad- rangle: State .Mineralogist's Kept. XXVII, 1931, pp. 56-00.

Cold deposits of the Retlding and Weaverville quadrangles: State Mineralo- gist's Rept. XXIX, 1933, pp. 2-73. Ayres, William O. — The ancient man of Calaveras (California) : Amer. Nat., vol. 16, 1882, pp. 845-854.

Gravel deposits of the lower Klamath : Min. & Sci. Press, vol. 50, 1885, p. 391

Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 209

Becker, George F. — Structure of a portion of the Sierra Nevada of California: Bull. Geol. Soc. Amer., vol. 2, 1891, pp. 49-74.

Antiquities from under Tuolumne Table Mountain in California (with dis- cussion by G. F. Wright) : Geol. Sue. Amer., Bull. 2, IS'Jl, pp. 1S9-198.

The Witwatersrand Banket with notes on otht-r gold-bearing pudding stones : U. S. Geol. Survey, ISth An. Kept., ISDii (California), pp. i2-i[i.

Auriferous conglomerates of the Transvaal: Amer. Jour. Sci. (4), vol. V, 1898, pp. 193-20S (including notes on California). Becker, George F., Lindgren, W., and Turner, H. W. — Description of the gold belt: U. S. Geol. Survey, Sonora folio, 41, 1897 ; Bidwell Bar folio, 43, 1898 ; Downie- ville folio, 37, 1897. Blackwelder, Eliot — Pleistocene glaciation in the Sierra Nevada and the Basin Ranges : .Geol. Soc. Am. Bull., vol. 42, 1931, pp. S65-922.

Glacial and associated stream deposits of the Sierra Nevada : State Mineral- ogist's Kept. XXVIII, 1932, pp. 303-310.

Eastern slope of the Sierra Nevada: XVI Nat. Geol. Congress Guidebook 16, Ex. C-1. 1933, pp. 81-102. Blake, Theodore A. — Remains of the Mammoth and Mastodon in California: Am. Jour.

Sci. (2), vol. 19. 1S55, p. 133. Blake, William P. — On fo-ssils in the auriferous rocks of California: Am. Jour. Sci. (2), vol. 43, 1867, pp. 270-271.

Note on a large lump of gold found on the middle fork of the American River: Calif. Acad. Nat. Sci., Proc. 3, 1868, p. 166.

1. New locality of fossils in the gold-bearing rocks of California: pp. 289- 290. 2. Tooth of the extinct elephant, Placer County: p. 290. 3. Quarry of gold- bearing rock: pp. 290-291. Calif. Acad. Nat. Sci., Proc. 3, 1868, pp. 289-291.

On a fossil tooth from Table Mountain: Am. Jour. Sci. (2), vol. 50, 1870, pp. 262-263.

The various forms in which gold occurs: Rept, Director of the Mint, 1SS4, p. 573-597 (1885). Bordeaux, Albert F. J. — Les anciens chenaux auriferes de Californie : An. Mines (10),

vol. 2, 1902, pp. 217-258. Boutwell, J. M. — The Calaveras skull' (shown to be of recent origin) : U. S. Geol. Survey,

Prof. Paper 73, 1911, pp. 54-55. Bowie, A. J. — Hydraulic mining in California: Amer. Inst. Min. Eng., Trans. 6, 1879, pp. 27-100.

Mining debris in California rivers : Trans. Tech. Soc. Pac. Coast, vol. IV, Feb.-March, 1887.

A practical treatise on hydraulic mining in California: New York (Fifth Edition), 1893. Bradley, Walter W. — Renewed activity in California gold mining: Min. & Met., vol. 13, 1932, pp. 385-390.

Itinerary, Yosemite to Mother Lode: XVI Int. Geol. Congress, Guidebook 16, Ex. C-1, 1933, pp. 62-65.

An echo of the days of '49: Eng. & Min. Jour., vol. 135, 1934, pp. 494-496. Brewer, William H. — Alleged discovery of an ancient human skull in California: Am.

Jour. Sci. (2), vol. 42, 1866, p. 424. Brooks, E. F. — Platinum in California: Min. & Sci. Press, vol. 114, 1917, p. 116. Brown, C. J. — Hydraulic gold mining: Min. & Sci. Press, vol. 31, 1875, pp. 50, 114, 161,

178, 313, 316; vol. 32, 187C, pp. 50, 89, 121. Browne, John Ross — Report on the mineral resources of the States and Territories west of the Rocky Mountains: U. S. Treasury Dept., 1868. Resources of the Pacific slope: New York, 1869. Browne, John Ross, and Taylor, James W. — Reports upon the mineral resources of the

United States: U. S. Treasury Dept.. 1867. Browne, Ross E.- — The ancient river beds of the Forest Hill divide : State Mineralo- gist's Rept. X, 1890, pp. 435-465. With maps, sections, and plates.

The channel system of the Harmony Ridge, Nevada County : State Mineralo- gist's Rept. XII, 1894, p. 202.

California placer gold: Eng. & Min. Jour., vol. 59, 1895, pp. 101-102. Gold in ancient California river channels: Min. & Sci. Press, vol. 77, 1898, pp. 107-108 ; (Mysteries of the ancient rivers of the Forest Hill divide, Placer Co., CaUf.): vol. 78, pp. 285-290. Bryan, Kirk — Geology and ground-water resources of Sacramento Valley, California:

U. S. Geol. Survey Water-Supply Paper 495, 1923, 285 pp. Bush, Edgar — Active placers in southern California: Min. Jour. (Ariz.), vol. 16,

1932, p. 7. Casey, Thos. Lincoln — Mining debris, California: 51st Congress, House of Rep., Ex.

Doc. 267, 1891. Cassidy, Andrew — The California Blue Lead in Oregon and Washington Territory :

Min. & Sci. Press, vol. 30, 1875, p. 82. Chaney, Ralph W. — Age of the auriferou.s gravels: (Abstracts) Bull. Geol. Soc. Am., vol. 43, 1932, pp. 226-227; I'an. Am. Geol., vol. 53, 1931, p. 361; vol. 56, 1931, pp. 71-72.

Notes on occurrence and age of fossil plants found in the auriferous gravels of Sierra Nevada: State Mineralogist's Rept. XXVIII, 1932, pp. 299-302.

Further evidence regarding the age of the auriferous gravels: (Abstract) Bull. Geol. Soc. Am., vol. 44, 1933, p. 78. Chase, A. W. — The auriferous gravel deposit of Gold Bluffs: Am. Jour. Sci. (3), vol. 7,

1874, p. 379. Cleaveland, Newton — Giant gold dredges at Natoma, California: Min. & Sci. Pre.ss,

vol. 103, 1911, pp. 446-448. Crampton, F. A. — .Vuriferous gravel channels in Nevada County: Min. Jour. (Ariz.).

vol. 16, no. 6, 1932, pp. 5-7. Cranston, R. E. — Mechanical features of the California gold dredge : Min & Sci Pre*;s vol. 104, 1912, pp. 303-307, 338-342, 372-375.

210 PLACKK MIMXG FOU COI.I) IN (AI.IFOWMA [r>ull. V.]')

Cronise. Titus l->v — Tlu- ii:iliir;il woallli ..f ('uliic.niia : II. H. Daiioroft & ("..., San

Francisco, 1S68. pp. 41(;-4;!;!, .j;U-.'.47. Crossniiin, J. M. — AurilViuiis gravels ..I San liabrid Kaniro, San Dti iiarditio <"i.iMily:

State Mineialunists Ui-pt. IX. -|s>;ii. pp. l-iW-lM. David.son, GeoPKc — on thi- anrilVnms uravtl dcpusits of California: Calil'. ail Si i., Proc. .'.. 1S7:!, pp. 1-I.")-H.

Gravels in Placer (.'ount.v, California: Calif. Acad. Sci., Proc. .'.. 1ST.'., p. 41. Davis, Horace — On anrifeious rravels near Sonura, California: Calif. Acad. .\at. .Sci.,

Proc. 1, isr..'., p. t;i ; 2d edition, lS7:f, p. di". Day, David T. — Platimini : .\Iin. & Sci. Press, vol. 7S. IS'.c.i. p. SS.

Notes on the occnn-eni-e of platinum in North America: Trans. .\ni. Inst. .Min. Eng-., vol. I'.'OO, p. 702. Dav, David T., and Richards, K. H. — Useful min<-rals in the black sands ..i ili.- Pa<l(i<-

slope: U. S. Oeol. Survey, Min. lies. f<ir l!iO."i (1006), pp. 1 17.")-1 2.".S. De (root, Henry — Hydraulic and drift mining: State Mineralogists Kept. II, ls2, pp. i:<3-iyo.

Recollection of California mining life: Min. & Sci. Press, vol. 47, iss:'., pp. 292, :J20-321, 3:!0, :;4G, 3S2.

The San Francisco ocean placer — the auriferous Inacli sands: State .Min- eralogists Kept. IX, \S'.H), pp. 54.".-.'.47. De La Rouglisse — Note sur les mines d'or de (Jolden River (California): 4>l pp.,

Paris. ISSr.. De Launa\, D.- -( ienlugical d.s. lipliun of tlie ynld min.-s of the Transvaal Wil wat.-rs- rand, Heidell>erg, and Kerksdorp districts) : Trans. Inst. Min. KiiK., v..l. 11, IS'.iK (California, p. 4:!4).

Alluvions auriferes de Californie: In L. De Uiunay. 'I'raile >U- Melal-

logenie Cites Minerau.x et Metalliferes. vnl. :!. Paris el l.iege. pp. 7ii.".-712.

Dickenson. Roy K. — The lone fornialiun of th<- Si.tia .Vevada footliills, a Incal facies

of the upper Tejon-Kocene : Science (n. s. ). v.. I. 40. 1!'14, pp. 07-70. Diller, J. S. — Notes on the geology of northern California: U. S. Cenl. Survey Dull. :::!, 1SS6.

Geology of the Lassen Peak district : V. S. Geol. Survey, th An. Rept., ISS'.I, pp. 39.J-432.

Geology of the Taylor.-ville r.-ui-.n California: Dull. C.nl. .v,,,-. .\ni.. vl. :!, l.S!i2, pp. 369-304.

Cretaceous and earlv Tcrtiarv nortliern Califurnia ami Oregon : Pull. Ct-nl. Soc. Am., vol. 4, 1893, pp. 203-224.

. . . on the auriferous gravil ville, California: Am. .lour. Sci.

Revolution in the topography of t

period: Jour. Geol. vol. 2, 1S94, pp. ,iL'-

Tertiary revolution in tlie topofii

vey, 14th An. Rept., pt. 2. 1S94, pp. 1

La.ssen Peak folio (.\o. 1.-. ) : P. S

GeomorphogiMi.v of the Klamail

Bull. 12. 1901. p. 4C1.

Topographic development of tin Bull. 196, 1902.

Mineral resources of the Indian legion. California : P. Geol. Survey, Bull. 260, 1904, pp. 4.'>-49.

Redding folio (No. 13S) : U. S. Geol. Survey, lOdil.

Geology of the Taylorsville region, California: P. S. Geol. Survey, Pull. :!.".:'., lOOS, p. 12S.

The auriferous gravels of the Trinity River Basin, i 'alifoi iiia : P S. CiiiA. Survey, Bull. 470. 1911, i)p. 11-29.

Trinity River gravels, California: f:ng. &; Min. Jour., vol. 92, P.' 1 1 , pp.

Auriferous gravels in the Woaverville quadranele, California: P. S. Geol. Survey, Bull. r.40, 1914, pp. 11-21. Dolbear. S. H. — Dry plac.r mining in California: Eng. <Ji -Min. ,Iour., vol. S9. 1910, p. :;.-|9. Donnelly, Maurice — Geology and mineral deposits of the .lulian district. San Diego County, California: State lineralogist's Rept. XXX, P.i"4 (plae.r deposits), p. 309. Do<,little, J. E. — Gold dredging in C.ilifoi nia : Cal. Stat." Min. Pur.. Bull, .-.fi, 19(i:,. Dragaje de oro en California: Bol. Soc. Nac. .Min. CI), vol. IS, 1907. pp. Dr<jn, R. W. — Gold mining in the Sieira .Nevada, California: ibol. Soc. Glasgow,

Trans. 11, 1900, pp. 203-206. Diiling, John F. — Geophsics as an aid in gold ])lacer iltilt mining: .\lin. Jour. (.\ri-/..),

vol. PS, Mar. 30, 1933. pp. .'. Dunn, R. L.— Drift mining in C.ilifornia: State .Mineraloni.-fs It.pt. N'lII. isss, i.p.

River mining: State .Miueralonisfs Rept. IX. IS'.mi, pp. 202-21. Aurifi'rous conglomerate in California (Siskiyou Coiintv) : State .Mineral- ogists Rept. .XII, lS93-l.S!i|. pp. 4.".:t-471. K<lil.\. L. H. — Dredg.-s on uppei Ameriean River: Kng. iVl Min. .I..ur., vol. '.i:;, pil2,

pp. 997-1(100. Edman, J. A. — .Votes on the gold hearina hhu'k sands of Califoniia : .Min. iVc Sel. Pr.ss, vtd. 09. l.sy4, pp. 291. ;!3ii. .;72.

Platinum minerals of Pluma> Co , California: .Min. .Sei. Piess, vol. 77. 1S9S. p. 4(1.

The auriferous l.la<-k sands of California: Cal. State Min P.ur. Pull. 4.", PMi7. pp. 5-10. lOng. .Mill. J.iur., vol. 1907, pp. Hi47-ln4s. Lflner. A. E. — Beach mimng with surf washer: .Min. & Sci. Press, vol. 80, 1903, p. 304. Egleston, T— The lorinaiion of yohl nuggets and placer deposits: Trans.. ,\mer. Inst. .Mm. Eng., vol. 9, ISsi, pp. i;33 (146.

, oo 'o'li'iP placer ileposits in the United St.ites : School Minos Quart., vol. 7, 1S86. pp. 101-131.

Diift mining: S.hool .Mines (Juart., \ol. S. 1SS7, pp. 201-220.

nortliern California ami (

Pull, t

of lacustral origin in the r

-f Tayl

Vol. 40. Is9:',. ))p. :!'.i9.

tile Pac'ific Coast since tlie :

a mile)

aphv of ih.. Pacili<- eoast :

U. S,

(iiiil. ;

;. G. oi. SuiM ]s'.<r,.

Ii .Mountains; (Alistracl)

Geril.

S..C. .

Klamath Mountains: P.

S. Gt

ol. Sui

Sec. II] GEOLOGY OF PLACER DEPOSITS — JENKINS 211

Ellsworth, Elmer W., Tracing burled-river channel deposits by geomagnetic methods:

State Mineralogists Kept. XXIX, 193H. pp. 244-200. Endlich, P. M. — Mining in the Mojave Desert in California (Goler Dry Placers) : Kng.

& Mln. Jour., vol. G2, 1896, pix I'JT-l'JS. Eteson, A. C. — Suggestions on inland gold dredging: Min. & Sci. Press, vol. 81, 1900,

p. 597 ; vol. 82, 1901, p. 36. Fairbanks, Harold W. — Geology of the Mother Lode region : State Mineralogist's Kept. X, 1S90, pp. 23-90, map.

Red Rock, Goler, and Summit mining districts in Kern County : State Min- eralogist's Rept. XII, 1893-1894, pp. 456-458.

Auriferous conglomerate in California: Eng. & Min. Jour., vol. 59, 1895, pp. 389-390.

Red Rock, Goler, and Summit mining districts in Kern County : Min. & Sci. Press, vol. 70, 1895, pp. 241, 245. Ferguson, H. G., and Gannett, R. W. — Gold quartz veins of the Alleghany district,

California: U. S. Geol. Survey Prof., Paper 172, 1932. Foster, G. G. — The gold regions of California: New York, 1848. Franke, Herbert A. — Selected bibliography on placer mining: State Mineralogist's

Rept. XXVHI, 1932, pp. 219-224; XXX, 1934, pp. 283-289. Fuchs, Edmond — Note sur les graviers auriferes de la Sierra Nevada de California:

Soc. Geol., France, Bull. (3) 13, 1885, pp. 486-488. Fuchs, Edmond, and de I-aunay, L. — Alluvious aurlf6res de California: In Trait6 des

Getes Mineraux et Miallifres, vol. 2, Paris, 1893, pp. 961-969. Gardner, E. D., and Johnson, C. H. — Placer mining in western United States: U. S.

Bur. Min., Inf. Cir. 6787, 1934, pp. 1-89. Gibson, Arthur — Magnetometric determinations applied to placer mining: Eng. & Min. Jour. Press, vol. 114, 1922, pp. 1064-1069. (California.)

Auriferous placer resources of California: Min. Cong. Jour., vol. 13, 1927, pp. 476-479. Gilbert, G. K. — Stages of geologic history of Sierra Nevada: Wash. Phil. Soc, Bull. 9, 1887, p. 7.

Terraces of the high Sierra, California: (Abstract) Science, (n.s.), vol. 21, 1905, p. 822.

Transportation of detritus by Yuba River: (Abstract) Bull. Geol. Soc. Am., vol. 19, 1908, pp. 657-659.

Quantity of mining debris: U. S. Geol. Survey, Prof. Paper 73, 1911, pp.

Hydraulic mining debris in the Sierra Nevada: U. S. Geol. Survey, Prof. Paper 105, 1917, 154 pp. Gledhill, Edward — The analogy between the gold "cintas" of Colombia and the aurifer- ous gravels of California: Trans., Inst. Min. Eng., vol. 20, 1902, pp. 391-400. Goldstone, L. P. — Fresno, Sierra, and Tuolumne Counties: State Mineralogist's Rept. X,

1890, pp. 734-738. Goldsmith, E. — The blue gravel of California: Acad. Nat. Sci., Phila., Proc. 1874,

pp. 73-74. Goodyear, W. A.-The auriferous gravels of California: Min. & Sci. Press, vol. 39, 1879,

pp. 182-183. GrifHn, F. W. — The gold dredging industry: Mln. & Sci. Press, vol. 88, 1904, pp. 260-261. Recent developments in gold dredging: Min. & Sci. Press, vol. 97, 1908, pp. 219-223. Gruetter, F. W. — Platinum on the Pacific Coast: Min. & Sci. Press, vol. 113, 1916,

pp. 20-21. Halev, Charles S. — Dry placers of southern California: State Mineralogist's Rept. XVIII, 1922, pp. 321-324.

Progress report on placer gold investigation : State Mineralogist's Rept. XVIII, 1922, pp. 373-374.

Tertiary sluice robbers: State Mineralogist's Rept. XVIII, 1922, pp. 550-553. Gold placers of California: Cal. State Min. Bur., Bull. 92, 1923, 167 pp. including maps and charts.

Primary and secondary gold concentrations : State Mineralogist's Rept. XIX, 1923, pp. 38-40. Hall, C. L. — The gravel fields of Northern California: Min. & Sci. Press, vol. 74, 1897,

p. 113. Hall, Frank H. — Ancient gravels, Siskiyou County, California : Min. & Sci. Press, vol. 66,

1893, p. 85. Hammond, John Hays — The auriferous gravels of California: In H. C. Burchard Report of the U. S. Director of the Mint upon the statistics of the production of t'le precious metals in the United States for the Calendar Y'ear 1881, pp. 616-630 (1882).

Auriferous gravels of California ; geology of of their occurrence and methods of their exploitation; State Mineralogist's Rept. IX, 1888-1889, pp. 105-138. Hanks, H. G. — Placer, hydraulic, and drift mining: State Mineralogist's Rept. II, 1882, pp. 28-192.

Placer Gold : In H. C. Burchard, Report of the U. S. Director of the Mint upon the statistics of the production of the precious metals in the United States for the Calendar Year 1882, pp. 728-732 (1883).

Gold in river channels: Min. & Sci. Press, vol. 58, 1S89, p. 485.

Deep gold placers of California : Min. & Sci. Press, vol. 60, 1890, pp. 231, 237,

249, 255, 264, 271, 280, 296, 314, 315, 330, 331, 337, 347, 353, 361, 362, 378, 384.

The deep-lying auriferous gravels and table mountains of California : San

Francisco, 1901, 15 pp.

Hanna, G. Dallas — Mammoth tusks found near Oroville, California: State IVIineralo-

gist's Rept. XXV, 1929, pp. 88-90. Hay, Oliver P. — The geological age of the Tuolumne Table Mountain, California : Wash. Acad. Sci. Jour., vol. 16, 1926, pp. 358-361.

The Pleistocene of the western region of North America and its vertebrated animals: Carnegie Inst. Wash., Publ. No. 322 B, 1927.

212 PLACER MINING FOR GOLD. IN CALIFORNIA [Bull. 135

JleilaiKl, (J. A., and Courtier, VV. H.- -Magiietometric investigations of gold placer deposits near Golden, Colorado : Am. Inst. M. & M. Kng., Geophysical Prospecting. 1'J2'J, pp. :{04-3S4. (Notlilng on t:alifornia. )

Hershey, t ). H. — Neocine deposits of tlie Klamath region, California: Jour. tJeol., vol. 10, iyo2, pp. :iT7-:r.i2. . , .., .

A supposed larly Tertiary peneplain in the Klanuith region, California: Science (n. s.), vol. 10, 1902, pp. la'J-lofi.

The signiticance uf certain Cretaceous outliers in the Klamath ngion, Cali- fornia : Am. Jour. Sci. (4), vol. H. l'.io2, p. 33.

The relation between certain river terraces and the glacial siries in north- western California: Jour. (Jeol., vol. 11, l'J03, pp. 4ai-4r>N.

Certain river terraces of the Klamath river region, California: Anur. Jour. Sci. (4), vol. 10, l!)0:i, pp. 240-250.

The river terraces of the Orleans Basin, California: Univ. Cal., Bull. Dept. Geol. Sci., vol. 3, l'J04, pp. 423-475. Hill, James M. — The mining districts of the western United States: Introduction by W. Lindgren: U. S. Geol. Survey, Bull. 507, 1'J12 (California), pp. 5-43.

The l.os Burros di.-trict, Monterey County, California : U. S. Geol. Survey, Bull. 735, 1923, pp. 323-329.

California gold production, 1S49-1923 : Econ. Geol., vol. 21, 192G, pp. 172-179. Historical summary of gold, silver, copper, lead, and zinc products in California, 184S-

1926: U. S. Bur. Min. Ec, Paper 3, 1929. Hinds, N. E. A. — Geologic formations of the Redding-Weaverville districts, Northern California: State Mineralogist's Kept. XXIX, 1933, pp. 114-122.

Late Cenozoic history of southern Klamath Mountains: (Abstract) Pan. Am. Geol., vol. 51, 1934, pp. 315-316.

Mesozoic and Cenozoic eruptive rocks of the .southern Klamath Mountains, California: Univ. Cal. Publ., Bull. Dept. Geol. Sci., vol. 23, 1935 (Tertiary), pp. 367-377. Hinds, N. E. A., and Russell, D. R. — lone formation of the Redding district: (Summary

statement) Pan. Am. Geol., vol. 51, 1929, p. 375. Hitchcock, C. H. — The Calaveras skull: Eng. & Min. Jour., vol. 9, 1870, pp. 345-346. Hittell, John S. — The dead rivers of California: Overland Monthly, vol. 1, 1S6.S, pp.

Dead rivers of California : In R. W. Raymond, Second Report on Mineral Resources of the States and Territories west of the Allssissippi, 1870, pp. 63-67. Hobson, J. B. — Placer County: State Mineralogist's Rept. X, 189U, pp. 410-434. Hoffman, Charles F. — The Red Point drift gravel mine : Trans. Tech. Soc. Pacific Coast,

vol. 10, No. 12, San Franciscu. 1894, pp. 291-307. Holmes, W. H. — Review of the evidence relating to auriferous gravel man in California : Amer. Anthropologist (n. s), vol. 1, 1899, pp. 107-121, 614-645; Smiths. Inst. An. Rept., 1899, pp. 419-472 (1901). Holmes, W. H., and McGee, W. J. — Geology and archeology of the California gold belt:

(Abstract) Am. Geol., vol. 23, 1899. pp. 96-99. Horner, R. R. — Notes on the black .sand deposits of southern Oregon and northern

California: U. S. Bur. Min., Tech. I'aper 196, 191S. Hubbard, J. D. — Drift mining in California: Eng. & Min. Jour., vol. 104, 1917, pp.

Hulin, Carlton D. — Geologic features of the drv placers of the northern Mojave Desert ;

State Mineralogist's Ropt. XXX, 19:!4, pp. 417-426. Hurst, (;. L. — Re.soiling after dredging in California: Min. & Sci. Pre.ss, vol. 107, 1913,

pp. 719-720. Hutchins, J. P. — The nomenclature of modern placer mining: Eng. & Min. Jour., vol. 84,

1907, pp. 293-296. Irvine, C. D. — The beach placers of the south Pacific Coast: Min. World, vol. 29, 190S,

pp. 321-322. Jackson, C. F., and Knaebel, J. B. — Small-scale placer mining methods: U. S. Bur.

Mines, Inf. Cir. 6611, 1932. Jacobs, H. S. — Ancient river channels (California) : Min. & Sci. Press, vol. 34, 1877,

p. 264. Jakosky, J. J. — Practical aspect of geophysical surveys: Min. Jour. (Ariz.), vol. 14, No. 16, 1931, pp. 7-8.

Use of geophysics in gold mining: Min. Jour. (.\riz. ), vol. 15, no. 6, 1931, pp. 5-7. 37. Jakosky, J. J., and Wilson, C. H. — Use of geophysics in placer mining: Min. Jour. (Ariz.), vol. 16, No. 14. 1929, pp. 3-4.

Geophysical studies in placer and water-supply problems: Am. Inst. M. & M. Eng., 'I'ecli. Publ. 51.'). 1934 (Trinity County placers), jip. 6-12. Jamison, C. E. — Santa (,'lara Placers: (Los Angeles and Ventura Counties). Min.

& Sci. Press, vol. 100, 1910, pp. 360-361. Janin, Charles — I'resent day problems in California gold dredging: Min. & Sci. Press, vol. 103. 1911, pp. 474-478.

Present day problems in California gold dredging: Trans., America Inst. Min. Eng., 42, 1912, pp. 855-873.

Placer mining methods and operating costs: U. S. Bur. Min., Bull. 121, 1916, pp. 42-58.

Topography and geology of dredging areas: Min. & Sci. Pre.ss, vol. 117. 1918. pp. 763-764.

Gold dredging in the United States: U. S. Bur. Mines, Bull. 127, 191.S. Proposed regulation of gold-<lredging : Min. & Sol. Press, vol. 106, 1931, pp. 381-384. Janin, Charles, and Winston, W. B. — Gold dredging in California: Cal. State .Min. Bur.

Bull. 57, 1910. Jenkins, Olaf P. — Report accompanying geologic map of northern Sierra Nevada : State Mineralogists Rept. XXVIII, 1932, pp. 279-298.

Geologic map of northern Sierra Nevada showing Tertiary river channels and Mother Lode Belt: Cal. State Div. Mines, 1932; later reprinted, with modi- fications and report accompanying, printed un back of map.

Se(;. II| (iKOLOGV OF I'LACKU I)K1-()SITS — .IKXKINS 213

.IcnkiiiH, olaf P. (Cont.)

I'se of KfoloKV in scekiriK pold : Min. Jour. (Ariz.), vol. 17, June 1), l'J.,-i, p. ... .Middle California and Western Nevada: XVI Int. Geol. Congres.s, Guide- book 16. Ex. C-1, iri.'?.'',.

Current note.s : (with notes on Beopli.vsical prospecting of buried river chan- nels by William U. Wright, Jr.), Stale Mineralr.isfs Ilept. XXX, l!t:',4, pp. :{-4. U'Surrection of earlv surfaces in the Sierra Nevada, a funrlamental geologic process involved in placer gold deposition: Cal. State .Mineralogist's liept. X.XX, in.34, pp. 5-r,.

(ieologic map of .Mother Iode Belt and vicinity d'J.'iL') : In State I)iv. .Mmes lUill. 108, by C. Logan, IH.'U. Jenkins, Olaf I'., and AVrigbt, W. Quinby— California's gold-bearing Tertiary channels:

Kng. & .Min. Jour., vol. 1 :!.'., lli:!}, pp. 4'J"-r)02. Kellogg, A. E. — Origin of flour gold in black sands: Min. .lour. (Ariz.), vol. U, no. 20,

l!i;U, pp. :i-4. Kenii), J. F.--l'latinuiii and associat.nl m.tals : U. S. Ceol, Surv.y, Hull. UCi, lli02,

l)p. ')1 Kimble, C.eorge W. — The Kimble Drift mine, El iJoradcj County, California: Min. & Sci. I're.ss, vol. .sr,, iiM)2, p. 2:i.

Ancient river channels California: Min. & Sci. Press, vol. 94, I'.tO,, pp. Knopf, Adolph, The .Mother Lode systt-m of California : U. S. Ceol. Survey, Prof. Paper l.")7, i:)29.

Tertiary auriferous gravels: .XVI Int. Geol. Congress, Guldel)ook ir,, Ex. C-1. I'J'.'i'i, pp. (JO-Gl. Knowlton, E. H. — Flora of the auriferous gravels of California: U. S. Geol. Survey,

Prof. Paper 7:'., lUll, pp. .")7-.jS. Knox, N. 13. — Dredging and valuing dredging ground in Oroville, California : Canadian

.Min. Pev., vol. 22, l!i03, pp. 211-213. Koch, Felix J. — The Calaveras .skull: Amer. Anticiuarian, vol. 33, 1911, pp. 199-202. Laizure, C. .McK. — lOlementarv placer mining methods and gold-saving devices: State Mineralogists liept. XXVIII, 1932, pp. 112-204.

Elementary placer mining in California and notes on the milhng of gold ores: State .Mineralogist's Itept. XXX, 1934, pp. 121-2S9. Lakes, .Arthur — The deep leads of California: Colliery Eng., vol. 14, 1S94, p. 170; Mm. & Sci. Press, vol. 6.S, 1S94, p. ISf,.

Fossilized big trees, California: Sci. .\m. Supl. 39, 1S95, p. 15862. Placer mining in (.California: Mines and .Minerals, vol. 19, 1899, pp. 297-29S. Gold bearing beach sands of California: .Mines and Minerals, vol. 19, 1899, p. 3(;9.

Calaveras County mines (California) : Mines and Minerals, vol. 20, 1899, pp. 198-200. Lang, Herbert — Black sand of the Pacific Coast: Min. & Sci. Press, vol. 113, 1916, pp.

Laur, P. — Terrains auriferes de la Californie : Rv. des deux mondes 33 annee (second

period), 1863, pp. 453-472. .

Lawson, Andrew C— The geology of Middle California: XVI Int. Geol. Congress, Guide- book 16, Ex. C-1, 1933, pp. 10-12. Laylander, K. C. — Magnetometric surveying as an aid in exploring placer ground :

Eng. & Min. Jour., vol. 121, 1926, pp. 325-328. Le Conte, Joseph — Post-Tertiarv elevation of the Sierra Nevada shown by the river beds: Am. Jour. Sci. (3), vol. 132, 1886, pp. 167-181.

The old river beds of California: Am. Jour. Sci. (3), vol. 132, 1886, pp.

On the origin of normal faults and of the structure of the Basm region : Am. Jour. Sci. (3), vol. 138, 1889, pp. 257-263.

Critical periods in the history of the earth: Univ. Cal., Bull. Dept. Geol. Sci., vol. 1, 1895, pp. 213-336. Leidv, Joseph — Remarks on vertebrate fossils from Table Mountain, Tuolumne Co., Cal. : .Acad. Nat. Sci., Phila., Proc. 1870, pp. 125-227.

Notes on Pleistocene mammals in California : In Whitney, J. D., "Auriferous gravels of the Sierra Nevada of California." Harvard Coll., Mus. Comp. Zool., Mem. 6, 1880, pp. 256-258; (another edition) Whitney, J. D., "Contributions to American Geology," vol. 1, 1880, pp. 256-258. Les(iuereux, Leo — Reports on the fossil plants, etc. : Mem. Mus. Comp. Zool. Harvard Coll., vol. 6, No. 2, Cambridge, 1878.

The Cretaceous and Tertiary floras: Rept. U. S. Geol. Geog. Survey, Terr., ( Havden), vol. 8, 1883. Lindgren, Waldemar — Two Neocene rivers of California: Bull. Geol. Soc. Am., vol 4, 1893, pp. 257-298.

An auriferous conglomerate of Jurassic age from the Sierra Nevada ; Amer. Jour. Sci. (3), vol. 48, 1894, pp. 275-280.

Sacramento folio (No. 5) ; U. S. Geol. Survey, 1S94.

The gold-quartz veins of Nevada City and Grass Valley districts, California : U. S. Geol. Survey, 17th Ann. Rept., Pt. 2, 1896, pp. 1-262. Nevada City folio (No. 29) : U. S. Geol. Survey, 1896. Pyramid Peak folio ( .Xo. 31) : U. S. (Jeol. Survey, 1896. Truckee folio (No. 39): U. S. Geol. Survey, 1897. Colfax folio (No. 66) : U. S. Geol. Survey, 1900.

The gold production of North America, its geological derivation and probable future: Int. Min. Congress, 5th Proc, 1903, pp. 29-36.

The geological features of the gold production of North America : Trans. Am. Inst. M. Eng., vol. 33, 1903, pp. 790-845, 1077-1083.

Neocene rivers of the Sierra Nevada: U. S. Geol. Survey, Bull. 213, 1903, pp. 64-65.

The Tertiary gravels of the Sierra Nevada of California: U. S. Geol. Survey, Prof. Paper 73, 1911.

214 PLACKR MlNINfl FOR GOLD IN CALIFORNIA [Bull. 135

Lindgron, Waldo-mar, and Knowlton, F. H.— Agre of the auriferous gravels of the Sierra Nevada, with a report on the flora of Independence Hill : Jour. Geol., vol. 4, 1896. pp. SSl-906. Lindgren, Waldemar, and Turner. H. W. — Placerville folio (No. 3) : U. S. Geol. Survey,

Marvsville folio (No. 17) : U. S. Geol. Survey, 1S95. Smart.sville folio (No. 18) : U. S. Geol. Survey. 1895.

Reprints from Placerville, Sacramento, and Jackson folio.<! (Nos. .1. 5, 11) : U. S. Geol. Survey. 1914. Lindgren, Waldemar, and others — The production of gold and silver in 1904 : U. S. Geol.

Survev. 100."); (California by Charles G. Yale. pp. 41-66). Locke A — Tuolumne Table Mountain (near Jamestown, California) : Min. & Sci. Press,

vol. 105. 1912, p. 85. Logan, C. A. — Platinum and allied metals in California: Min. Bur., Bull. 85, 1919.

Auburn field division : Amador, Nevada, Placer. El Dorado. Calaveras, Tuol- umne Counties: State Mineralogist's Rept. XIX, iy2;{, pp. i:!-21, 59-60, 94-97, 140-145,

Sacramento field division : Amador, Nevada, Plumas, Shasta, Sierra, Tuol- umne, M(ino, Placer, Sacramento, Yuba, Calaveras, El Dorado Counties: State Mineralogist's Rept. XX, 1924, pp. 1-23, 73-84. 177-1S3. 355-367.

Sacramento field division ; Sacramento, Calaveras, Placer Siskiyou Coun- ties: State Mineralogist's Rept. XXI, 1025, pp. 1-22. 135-172, 275-280, 413-498. Ancient channels of Duncan Canyon region. Placer County, California: State Mineralogist's Rept. XXI, 1925, pp. 275-280.

Sacramento field division; El Dorado County, California: State Mineralo- gist's Rept. XXII, 1926, pp. 397-452.

Sacramento field division; Trinity, Shasta, El Dorado Counties: State Min- eralogist's Rept. XXII, 1926, pp. 1-67, 121-216. 313-452.

Sacramento field division; Amador, Placer Counties. California: State Mineralogist's Rept. XXIII. 1927. pp. 131-202, 235-286. 373.

Sacramento field division ; Tuolumne County, California : State Mineralo- gist's Rept. XXIV, 1928, pp. 3-53.

Sacramento field division; Sierra County, California: State Mineralogist's Rept. XXV, 1929, pp. 151-212.

Sacramento field division; Butte County, California: State Mineralogist's Rept. XXIV, 1928, pp. 191-210; XXVI, 1930, pp. 383-407.

Sacramento field division; Nevada County, California: State Mineralogist's Rept. XXVI, 1930, pp. 90-137.

Mother Lode gold belt of California: Cal. State Div. Mines, Bull. 108, 1934, including 6 geologic maps. Louderback, George D. — Morphologic features of the Basin Range displacements in the Great Basin: Univ. Cal., Bull. Dept. Geol. Sci., vol. 16, 1826. pp. 1-42.

Notes on the geologic section near Columbia, California ; with special refer- ence to the occurrenee of fossils in the auriferous gravels ; Carnegie Inst. Wash., Publ. Paleo., vol. 440, 1934. p. 440. MacDonald. D. F. — The Weaverville-Trinity Centre gold gravels. Trinity County.

California: U. S. Geol. Survey, Bull. 430, 1910, pp. 48-59. MacGinitie. Harry — Ecological aspects of the floras of the auriferous gravels: (Abstract) Bull. Geol. Soc. Am., Proc. 1, 1934, p. 356; (Abstract) Pan. Am. Geol., vol. 42, 1934, pp. 75-76. Maclaren, J. Malcolm — Gold : Its geological occurrence and geographical distribution :

London, 1908 (California, pp. 503-514). Marcou, Jules — Sur le gisement de I'or en Californie: Arch. Sci. Phys. Nat, vol. 28, 1855, pp. 124-135. Also in his Geology of North America, Zurich, 1858, pp. 81-84. Matthes, F. E. — Geologic history of the Yosemite Valley: U. S. Geol. Survey, Prof. Paper 160, 1930.

Geography and geology of the Sierra Nevada: XVI Int. Geol. Congress, Guidebook 16, Ex. C-1, 1933, pp. 26-40.

Up the western slope of the Sierra Nevada by way of the Yosemite Valley : XVI Int. Geol. Congress, Guidebook 16. Ex. C-1. 1933, pp. 67-81. Maxson, John H. — Economic geology of portions of Del Norte and Si.skiyou Counties, Northwesternmnst California: State Mineralogist's Rept. XXIX. 1033, pp. 123-160. McGillivrav, J. J. — The old river beds of the Sierra Nevada of California: In H. C. Burchard, Report of the U. S. Director of the Mint upon the statistics of the production of the precious metals of the Ignited States for the Calendar Year 1881, pp. 630-644 (1882). Mendell, J. H. — Report upon a project to protect the navigable waters of California from the effects of hydraulic mining: In Repts. Chief Eng. U. S. Army; also House Ex. Doc. No. 98, 47th Cong., 1st sess., 1882. Merriam, John C, and Stock, Chester — Tertiary mammals from the auriferous gravels near Columbia, California: Carnegie Inst., Wash., Publ. Paleo., vol. 440, 1934. pp. 1-6. Miscellaneou.s — Statistical reports by the California State Mining Bureau, later called the Division of Mines.

California Miners' Association Annuals. Mineral Industries, McGraw-Hill.

Mineral Resources of the United States: U. S. Geol. Survey and later by U. S. Bureau of Mines.

Debris Commission reports. Nason, F. L. — The Colder gold diggings: Eng. & Min. Jour, vol. 59. 1890, p. 223. Oldham, C. — Placer gold discovery in Greenhorn Gulch: Min. Jour. (Ariz.), vol. 15,

no. 13. 1931, pp. 3-4. Pardee. .1. T. — Placer deposits of the western United States. In Ore deposits of the Western States: Am. Inst. M. & M. Eng. Publ., 1933, pp. 419-450.

Beach placers on the Oregon Coast: U. S. CJeol. Survey, Cir. 8, 1934, pp. 4-41. Patmon, C. G. — Methods and costs of dredging auriferous gravels at Lancha Plana,

Amador County, California: U. S. Bur. Min. Inf. Clr. 6659, 1932. Phillips, J. Arthur — A treatise on ore deposits: London, 2d edition, 1896 (California placers, pp. 19-27).

Sec. 11] GEOLOGY OF PLACEK DEPOSITS — JENKINS 215

Radford, G. K. — Mining for gold in the auriferous gravels of California: Inst. Min.

Eng., Trans. 17, 1900, pp. 452-481. Ransome, F. L. — Some lava flows of the western slope of the Sierra Nevada, California :

U. S. Geol. Survey, Bull. 89, 1898, 74 pp.

Mother Lode district folio (No. 6;j) : U. S. Geol. Survey, 1900. Ransome, P. L., and Turner, H. W. — Sonora folio (No. 41) : U. S. Geol. Survey, 1897.

Big Trees folio (No. 51) : U. S. Geol. Survey, 1898. Raymond, Rossiter W. — Mineral resources of the States and Territories west of the

Rocky Mountains: U. S. Treasury ., 1S69.

Statistics of mines and mining in the States and Territories west of the

Rocky Mountains: U. S. Treasury Dept., 1.S70-1S7G. Reid, J. A. — A Tertiary river channel near Carson City, Nevada: Min. & Sci. Press,

vol. 9G, 1908, pp. 522-526. Rensch, H. E. & E. G., and Hoover, Mildred B. — Hi.storic spots in California: Stanford

Press, 1933. Ricketts, A. H. — Manner of locating and holding mineral claims in California: Cal.

State Div. Mines, Bull, 106, 1931 (Placer locations, pp. 9-10). Richards, R. H., and Dav, D. T. — Investigation of the black sands from placer mines:

U. S. Geol. Survey, Bull. 285, 1906, pp. 150-164. Robinson, F. W. — Notes on hydraulic mining: State Mineralogist's Rept. II, 1882, pp.

Robinson, L. L. — Impounding reservoir for mining and other debris. House Com- mittee on water rights and drainage, Assembly Bill 451, Feb. 17, 1887. Romanowitz, C. M., and Young, George J. — Gold dredging: Eng. & Min. Jour., vol. 135,

1934. pp. 486-490. Rose, T. Kirke— The metallurgy of gold: 5th edition. London, 1906, pp. 45-92. Russell, Israel C.Rivers of North America : New York, 1898 (California, pp. 275-278). Sampson, R. J. — Placers of southern California : State Mineralogist's Rept. XXVIII

(Supplement), 1932, pp. 245-255. Sauvage, Ed. — De I'exploitation hydraulique de I'or en Calif ornie : An Mines (7), vol. 9,

1876, pp. 1-77. Scupham. J. R. — The buried rivers of California as a source of gold : Mines and Min- erals, vol. 19, 1898, pp. 150-152. Shimmer, G. L. — Ancient river channels of California: Eng. & Min. Jour., vol.- 114, 1922,

p. 857. Silliman, B. Jr. — On the deep placers of the South and Middle Yuba, Nevada County,

California: Am. Jour. Sci. (2), vol. 40, lSfi5. pp. 1-19.

On the existence of the mastodon in the deep-lying gold placers of Cali- fornia: Am. Jour. Sci. (2), vol. 45, 1S68, pp. 378-3X1.

Notice of the peculiar mode of the occurrence of gold and silver in the foot- hills of the Sierra Nevada, and especially at Whiskey Hill, in Placer County,

and Quail Hill, in Calaveras County, California: The Acad. Nat. Sci., Proc. 3,

1867, pp. 349-351; Am. Jour. Sci. (2), vol. 45, 1869, pp. 92-95. Simpson, Edward C. — Geology- and mineral df-posits of the Elizabeth Lake quadrangle,

California: State Mineralngi.t's Rept. XXX, 1934, (placer deposits, p. 409). Sinclair, J. — Recent investigation bearing on the question of the occurrence of

Neocene man in the auriferous gravels of the Sierra Nevada: Cal. Univ. Publ.

Am. Archaeology and Ethnology, No. 7, 1908, pp. 107-131. Skidmore. W. A. — Deep placer mining in California : In R. W. Raymond. Third Report

on Mineral Resources of the States and Territories west of the Mississippi, 1870,

pp. 52-90 (1872). , , „.

Hvdraulic mining at Gold Run — The Blue Lead ancient river channel : Mm.

& Sci. Press, vol. 30, 1875, pp. 108-169.

Gravel channels of ancient rivers: Min. & Sci. Press, vol. 51, 1885, p. 6. Smith, A. M., and Vanderburg, Wm. O. — Placer mining in Nevada: Univ. Nev., Bull.,

vol. 26, no. 8, 1932. Smith, J. P. — The geologic formations of California, with reconnaissance geologic maji :

Cal. State Min. Bur.. Bull. 72, 1916. Smyth, H. L. — Origin and classification of placers: Eng. & Min. Jour., vol. 79, 1905,

pp. 1045-1046, 1179-1180, 1228-1230. Sperry, E. A. — Investigation of Feather River black sands: Min. & Sci. Press, vol. 105,

1912. pp. 624-626. Steffa, Don — Gold mining and milling methods and costs at the Vallecito Western Drift

Mine, Angels Camp, California: U. S. Bur. Mines, Inf. Cir. 6612, 1932. Stewart, J. D. — Hvdraulic mining again interesting to capital: Eng. & Min. Jour.,

vol. 135, 1934; pp. 491-493. Storms, W. H. — Ancient channel system of Calaveras County: State Mineralogist's

Rept. XII, 1894, pp. 4S2-492.

Peculiar effect of subterranean corrosion of rocks (Tuolumne Co., Cal.) :

Min. & Sci. Press, vol. 79, 1899, p. 5.

Mother Lode region of California: Cal. State Min. Bur., Bull. 18, 1900. Ancient gravel channels of Calaveras County, California : Min. & Sci. Press.

vol. 91, 1905, pp. 170-171, 192-193. Taylor, G. F. — The Brandy City hydraulic mine. Sierra County (California) : Eng.

& Min. Jour., vol. S9, 1910, pp. 1152-1153. Theller, J. H. — Hydraulicking on Klamath River: Min. & Sci. Press, vol. lOS, 1914,

pp. 523-526. Thurman, C. H. — Possibilities of dredging in the Oroville district, California: Min.

& Sci. Press, vol. 118, 1919, pp. 257-258. Toleman, P. — Auriferous gravels of the counties : The Nevada City Nugget, Special

Mining Number, May 10, 1929, pp. 19-21. Trask, John B. — Report of First State Geological Survey, Sacramento, 1853.

Report on the geology of the Coast Mountains and part of the Sierra Nevada :

Calif. Assembly Doc. No. 9, Session of 1854.

Report on the geology of northern and southern California : Calif. Assembly

Doc. 14, Session of 1856.

216 PLACER MINING FOR OOLD IN CALIFORNIA [Bull. 135

Tucker, W. B. — Notes on activity In Inyo and Mono Counties In July, 1931: State MlneraloRlst's Rept. XXVII. 1931, pp. 543-546.

South of the ThM<>hapi i,'olil mitilnK makes new pain: Eng. &. Mln. Jour., vol. 135. 1935. pp. 517-521. Tucker, W. B., and Samp.<!on, R. J. — Los Angeles Field Division; San Bernardino County : State Mineralogist's Rept. XXVI, 1930, pp. 221-260 ; XXVII, 1931 (Gold), pp. 2S0-333.

Los Anceles Field Division; Ventura County (Gold): State Mineralogist's Rept. XXVIII, 1022, pp. 253-257.

Gold rpsoiirces of Kern County, California : State Mineralogist's Rept. XXIX, 1933, pp. 271-3.T0. Turner, H. W.— Mohawk lake beds: Bull. Wash. Phil, Soc, vol. 11, 1891, pp. 385-410. Jackson folio (No. 11) : IT. s. Geol. S\irvey, 1894.

The rocks of the Sierra Nevada: U. S. Geol. Survey, 14th An. Rept., pt. 2, 1894, pp. 441-495.

Auriferous gravels of the Sierra Nevada: Am. Geol., vol. 15, 1895, pp.

The age and succession of the igneous rocks of the Sierra Nevada: Jour. Geol.. vol. 3. 1S95. pp. 385-414.

Further contributions to the geology of the Sierra Nevada: U. S. Geol. Sur- vey. 17th An. Report, pt. 1, 1X06, pp. 521-762.

Bidwell Bar folio (No. 43) : U. S. Geol. Survey, 1898.

The occurrence and origin of diamonds in California: Am. Geol., vol. 23, 1S99, pp. 182. 191.

Post-Tertiary elevation of the Sierra Nevada: Bull. Geol. Soc. Am., vol. 13, 1003, pp. 540-541.

Cretaceous auriferous conglomerate of the Cottonwood Mining district, Sis- kiyou County. California: Eng. & Min. Jour., vol. 76. 190."?, pp. 653-654. Turner. H. W.. and Ransome, F. L. — Sonora folio (No. 41) : U. S. Geol. Survey, 1897.

Big Trees folio (No. 51) : U. S. Geol. Survey. 1808. von Bernewitz. M. W. — Dredging and resoiling: Min. & Sci. Press, vol. lis, 1919, p. 471. Weatherbee, D'Arcy — A hydraulic mine in California: Min. & Sci. Press, vol. 93, 1906, pp. 296-208.

Dredging and horticulture: Min. & Sci. Press, vol. 94, 1907, p. 151. Whitney, J. D. — Geological Survey of California, Geology: vol. 1, Philadelphia, 1S65. Notice of a human skull recentlv taken from a shaft near Angels, Calaveras County, California: Calif. Acad. Nat. Sci.. Proc. 3. 1867. pp. 277-278.

Sur les amas detrlliciue de la Californie : Soc. Geol., France, Bull. (2) 24, 1S67, pp. 624-625.

The auriferous gravels of the Sierra Nevada: Mem. Mus. Comp. Zool. Har- vard Coll., vol. 6, 1879, p. 659. Includes chapters by W. A. Goodyear and W. H. Pettee.

The climatic changes of later geological times: Mem. Mus. Comp. Zool. Har- vard Coll.. vol. 7. pt. 2. 18S4. p. 394. Wiel, S. C. — The ancient channel of Gibsonville, California : Mln. & Sci. Press, vol. 91,

1905. p. 73. Williams, Howel — Geology of the Afarysville Buttes, California: Univ. Cal. Dept. Geol.

Sci. Bull., vol. 18. 1929, pp. 103-220. Wilson, C. H. — Economic value of geophysics in mining: Min. Jour. (Ariz.), vol. 15,

no. 21, 1032, pp. 3-5. Winslow, C. F. — On human rcinains along with those of Mastodon in the drift of Cali- fornia : Boston Soc. Nat. His., Proc. 6, 1S57. pp. 278-270. Wright. G. F. — The lava beds of California and Idaho, and their relation to the antiquity of man: (Abstract) British Asso. Rept. 61. 1892, p. 651.

Evidence of Glacial man in America: (Abstract) Amer. (Jeol., vol. 12, 1S93, pp. 173-174.

Recent volcanic eruption in California : Amer. Nat., vol. 27, 1803, pp. 813-816. Recent date of lava flows in California: Records of the Past, vol. 4, 1005, pp. 19.5-198.

The latest concerning pre-historic man in California: Records of the Past, vol. 7, 1908. pp. 183-187. Yale, C. G. — Auriferous gravel — a theory of its formation : In H. C. Burchard, Report of the U. S. Director of the Mint upon the statistics of the production of the precious metals in the United States for the Calendar Year 1880, pp. 376-379 (1881).

Mining debris legislation: Cal. Mines Assoc, Mines and Minerals, 1889, pp. 255-262.

Beach mining in California: U. S. Geol. Survey, Min. Res. for 1912, pp. 253- 254 (1913).

Dry placers of California: U. S. Geol. Survey, Min. Res., pt. 1, 1913, pp. Yeatman. J. A. — The pump in placer mining: Min. & Sci. Pres-s, vol. 88, 1904, p. 226. Young, George J. — California's gold dredge in operation over twenty years : Eng. & Min. Jour., vol. 121, 1927, pp. 1042-1046.

Drift mining at Vallecito, Calaveras County, California: Eng. & Min. Jour., vol. 128. 1929. pp. 394-307. Zadarh, Stanley — Placer mining in San Gabriel Canyon: Min. Journ. (Ariz.), vol. 17, no. 3, 1933, p. 3.

Section Iii

Prospecting And Sampling Placer Deposits

Sampling

Nothing: is more important to the success of a placer mine than to determine in advance that the gravel in question contains enough gold and possibly metals of the platinum group, to return a profit. Money received for the metals sold must be sufficient to pay for the cost of operation plus the cost of all equipment plus royalties or cost of land plus interest on the investment plus a reasonable profit. Of course, if the equipment is to be used on more than one deposit, amortization of its cost may be distributed accordingly. A large proportion of all placer operations has failed because the gold in the gravel was insufficient to repay the cost of even the most efficient mining, not to mention the return of money* invested or interest thereon.

Many methods of sampling are available, including the simple panning of gravel from natural exposures, drifting, test-pitting or trenching, shaft-sinking, and churn-drilling. Actual mining on a small scale often is done as a method of sampling prior to investing considerable money in development or equipment. Panning, rocking, and small-scale machines have been described in Section I, under Small-Scale Methods. All of these are useful in prospecting and sampling. Small machines driven by gasoline engines have been much used in recent sampling jobs to save labor.

Weight of Placer Gravel

Placer gravels vary greatly in weight per cubic yard in place and percentage increase in volume on being loosened. Yet in making esti- mates of yardage and value it often is necessary to use some factor to convert volume in place into loose volume or into tonnage. In common placer terminology "heavy" gravel indicates coarse rather than weighty material. The weight is greater in tight or cemented than in loose ground, and it increases with the proportion of large boulders and heavy rock material such as diorite, greenstone, or hornblende schist. The amount of moisture present likewise affects the weight.

Three contiguous samples taken by Gardner and Johnson from the same bed of tight, fine clayey gravel overlying a pay streak in the Greaterville district, Arizona, indicated weights of 3,450 pounds, 3,540 pounds, and 3,000 pounds to the cubic yard, respectively, or an average of 3,300 pounds. A sample of clean gravel with 30 to 40 percent cobbles over 2J inches in diameter, from another gulch in the same district, weighed 3,600 pounds to the cubic yard in place. The samples contained 5 to 8 percent of moisture. The expansion of the first three samples was 50, 54, and 33 percent, respectively, an average of 46 percent. The last .sample expanded 17 percent.

The gold-bearing river gravel at the pit of the Grant Rock-Service Company, Fresno, California, weighs 2,850 pounds per cubic yard. Some engineers in calculating tonnage allow 3,000 pounds to the cubic yard, bank measure. Handbooks give weights per cubic yard ranging from 2,600 to 3,650 pounds. An average weight probably is between 3,000 and 3,300 pounds to the cubic yard.

' Gardner, E. D., and Johnson, C. H., Placer mining in the western United States, Part 1, General information, hand-shoveling, and ground-sluicing: U.S. Bur. Mines. Inf. Circ. 6786, p. 27, 1934.

(219)

220 I'LACKU MINING FOK GOLD IN CALirOKNIA [Bull. 135

Sampling Natural Exposures

Whonevor a 'old pan is used skillfully tlio result not only proves or disjjroves the preseju'e of i;old but also usually shows aeeurately the amount of prold contained iu the sample ehosen. l'annin<r along a creek bed thus is the most elementary' method of sampling a placer deposit. However, the samjiles commoidy are taken so as to render the quantita- tive results worthless.

A gravel deposit of much size seldom can be sampled directly from its natural exposures; but a few creek banks, steep-sided gulches, or old excavations such as hydraulic pits may be available, in which case certain precautions should be taken to get true samples. F'irst, the vertical extent of gravel to include in a given sample should be determined. If hydraulicking is to be done, the whole depth of gravel ordinarily is included in one sami)le, except when it is planned to pijie off the barren overburden to waste, in which event it is desirable to know the depth of barren material and samples may bo taken of each distinguishable stratum. If drifting is planned, only the lower, economically minable gravel need be sampled. After the location and extent of a sample cut have been decided, care must be taken to have equal (juantities of gravel from all points along its length. The best way to do this is to cut a chan- nel or groove of uniform shape and size from top to bottom of the sample distance. Enough such samples must be taken to prove the continuity of the "pay streak."

Mechanically the ]>rocedure of sampling a gravel face resembles closely that pursued in lode mines. A pan and a pick are the requisite tools. The bank should be trimmed well and cleaned ahuig the sample line to eliminate effects of surface weathering. The pan may be used to catch the loosened material, or a canvas may be spread on the ground. If conditions favor it, a measurable channel or groove should be cut so that the volume taken can be measured. Otherwise, the only alternatives are to use a factor for pans per cubic yard or to measure the loose gravel in a box which has been calibrated in terms of bank measure.

Drifting

Drifting is a common method of prospecting a deep placer deposit when coiulitions are favorable. The cost of driving a small drift in placer gravel ordinarily ranges from $2 to $(j per foot. Diflfieult ground conditions or excessive water may increase the cost to $10 or $15 per foot.

For sampling purposes the gravel usually is taken to the surface and concentrated in sluice boxes. If an old drift is being sampled various methods may be followed. If the ground will permit, the most .satis- factory method is to slab 1 or 2 feet from the side of the drift and wash the gravel thus broken. If not, vertical channels may be cut on one or both sides of the drift at intervals of about 5 feet. If the latter is done, the volume of the sample cut may be mea-sured, which is preferable under most conditions, or a factor may be used for reducing loose measures of gravel to solid measure, which facilitates taking the sample but intro- duces some uncertainty and leads to carelesness in sampling. If values are to be expressed in cents per ton it is still necessary to decide what conversion factor to use in making estimates of tonnage.

Sec. Ill] SAMPLING 221

Test-Pitting

Test-pittiiif? and ti-t'neliiiiL>- nrc fii)i)lii-al)lp only to i-avels so .sliallow that a man can throw out the dii't by hand. Tlie best procedure is to mark out the area of the pit on the surface, makinjr it rectangular, as small as convenient, and jireferably in dimensions of even feet such as 2 feet wide and 3 or 4 feet huig. Then it shouhl be excavated to bedrock with smootli, vertical walls. Sometimes a cleared space is prepared and the dirt thrown on the bare ground, but in view of the greater difficulty and possible small error involved in rehandling the dirt it is better to shovel it onto a canvas or board platform or into a receptacle. If a large boulder projects iiito the pit no correction of the theoretical volume of gravel should be made, regardless of whether or not the bo\dder is removed oi- allowed to remain in place, as obviously it can not be ignored in mining operatituis and is the equivalent of so much barren gravel. The gravel taken from the pit may be thrown into one or more piles, depending on whether or not information is desired regarding one or more individual strata. Sometimes alternate third, fourth, or tenth shovelfuls are used for the .sample to reduce the volume to be panned or otherwise concentrated. This should be avoided whenever practical because of the possible error introduced.

The cost of sinking test pits or running trenches in earth and gravel has been noted often enough for fair generalizations to l)e established. Gardner - states that opencast work in placer ground costs from $0.40 to $1 per cubic yard, depending on the nature of the ground and on wages. AVages for such work then ranged from $3 to $4 per 8 hours. Furthermore, a nuni should be able to pick and shovel about 8 cubic yards of fairly loose gravel in 8 hours. test pits the worker's efficiency would be lowered somewhat by the cramped quarters and by the care necessary to square out the corners and trim the sides to vertical planes.

The spacing of test pits depends on the nature of the deposit. If the pay gravel occurs in narrow channels the best plan is to space the pits in lines across the channels, as is done with churn-drill holes when sampling dredge ground. The holes must be close enough to yield an average value which represents the average value of the channel at that point. In practice the spacing ranges from a few to 50 or 75 feet, depending on the uniformity of results. The transverse lines of pits theoretically should be placed close enough to show either fairly uniform values from line to line or a rea.sonable upward or downward trend of gold content along the channel, rnfortunately, this is seldom po.ssible, and the usual practice of spacing the lines from 100 to several hundred feet apart is a compromise in the engineer's mind between the cost of sampling and the need for accurate results.

Shaft-Sinking Shaft-sinking is a connnon method of testing placer ground. Pros- pect and sampling shafts, unless intended for later use in drifting or mining and unless exceptionally deep (75 feet or more), are sunk as small as practicable. The u.sual section is rectangular and 3 by 4 to 4 by 6 feet in size. Kound timber 4 to 6 inches in diameter, which is available in most districts, is commonly used to crib shafts in loose gravel. In gravel tight enough to stand safely without lagging the only timber

- (jardner, E. D., Cost of mine opening.'; : Eng. and Min. Jour., vol. 100, pp. 791-794, Nov. 13, iyi5.

222 PLACKR MINING FOR GOLD IN CALIFORNIA [Bull, 135

necessary is .stalls sot to liold the ladder. A hand windlass is the usual means of hoistinjr, usiiijjf a light steel, 2-cu.ft. bucket and a f- or 1-inch- dianieter nianila rope, as ordinary wire rope is unsuitable for a windlass; 75 to 100 feet is the niaxiinuni depth at which such e(iuipnient can be used most efiiciently. For jreater depths a power hoist of some kind should be installed. Lar<re boulders can be lifted with the ordinary hand windlass if it is provided with long cranks; as nnicli as 800 pounds can be raised by two men. Such feats, however, are considered danjzerous because of the jreneral absence of safe brakes or catches on windlasses, and the possibility of killinj,' or injuring the operator if he loses control of tlie ci-ank handle.

All of the {gravel removed from such a sliaft is often trucked to a stationary washing plant to recover the gold. The gravel is dumped into a hopper from which it is fed to a revolving screen or trommel equipped with a water-spray, and undersize is washed in sluices. If these are placed in steps, so that the gravel drops from one to the next below, the necessity for tight cross-joints is avoided. Slopes of the boxes can be adjusted to give good recoveries for different types of gravel. In one actual case 4 boxes were used, each 10 feet long, 10 inches wide, and H inches deep. Grade of the fii'.st three boxes was set at inches per foot, and of the fourth at -i-inch per foot. In shafts that stand without timber, the gravel may be sampled by cutting a vertical channel. A common size is 1 foot wide and 1 foot deep. Care should be taken with bedrock, which should be removed for at least a few inches in depth, and then brushed clean. Ilecovered gold should be weighed on an accurate balance, and an occasional assay should be made to determine the fineness of the gold.

Where gravel is loose, sometimes steel tubes about feet in diameter, called caissons, are sunk as the shaft is excavated, to hold the walls. An example of this method in which telescoping caissons were used is given in the table at the end of this section. If the shafts are wet, and pumps driven by engines or motors are needed, this method becomes very expensive, and drilling may be used instead; although drilling is a less accurate method of sampling.

Drilling

Placer deposits, particularly those being considered for dredging, are often sampled by drilling, which could be called drive-pipe sampling with more accuracy. The casing, usually a G-iiu'h pipe with a special shoe, is driven a foot at a time into virgin gravel, then the core of grav?l that rises in relation to this pipe is cut by the bit of the churn-drill and bailed out with a sand pump. Water is added to all holes. The cut- tings from each foot are panned by an expert panner, and the weight of the gold in each i)an is estinuited. The colors of gold from the pans from a single hole ai"e combiiunl and amalganuited with a drop of quick- silver. This gold is later recovered fi-om the amalgam by the engineer and actually weighed.

The drill in common use is the Keystone, made by Keystone Driller Company, Heaver Falls, Pennsylvania. Califoi-nia agents arc Ilarron, Rickard and McCone Company, 2070 Bryant Street, San Francisco, or 3850 Santa Fe Avenue, Los Angeles. Late designs include model 70 mounted on a truck, and model 71 on crawler tracks. According to the

Sec. Ill] SAMPLING 223

manufacturer, model 71 will climb grades of 50 percent when loaded witli necessary tools and equipment.

The object of this type of drilling is not to make rapid progress with the hole but to get accurate samples. Drilling would proceed at a much greater speed if the bit of the churn-drill were kept ahead of the casing, but this is never done in sampling unless a boulder must be broken to allow driving of the casing, because the volume of gravel removed from the hole would not be known. When the casing is driven a foot at a time, volume may be calculated as that of a cylinder a foot long and with diameter equal to the outside diameter of the cutting slioe, usually inches. "Water is added to dry holes so that tlie cuttings may be with- drawn by means of a suction sand-pump. Water is added to wet holes to keep the water-level in the hole higher than the natural ground-water level. This helps to prevent excess material from entering the casing. When bedrock is reached, the casing can no longer be driven, but drilling is continued for a few feet to recover gold on bedrock and to make sure that the casing is not resting on a boulder. Sometimes the drill strikes a fissure in bedrock and an abnormal amount of gold is recovered. In such a case the panner should keep this gold separate from gold recovered from the gravel, and hand it to the engineer as a separate button of amalgam.

The engineer dissolves the mercury from the amalgam with nitric acid of specific gravity 1.42 diluted with an equal volume of distilled water, washes the gold well with boiling water, then dries and anneals the gold in a small porcelain cup. Sometimes a little alcohol is added to the wash-water to prevent sputtering when drying. The dried gold dust is weighed on a balance sensitive to a milligram or less. Fineness of the gold must be determined by an occasional fire-assay. If platinum is present, concentrates from panning must be saved and weighed, then sent for chemical analysis. The amount of gold in cents per cubic yard for the gravel removed from the hole is calculated as follows : W X M X 27

Dx 0.3068 in which V rvalue of the gravel in cents per cubic yard

W weight of gold recovered from the hole in milligrams M price in cents of a milligram of gold 27 number of cu. ft. in 1 cu. yd. D=depth of hole in feet 0.3068 area in square feet of shoe-circle 71 inches in diameter.

The value of M depends on the price of gold and its fineness. When

gold is $35.00 per ounce and the gold recovered is 900/1000 fine, it is

calculated as follows :

-, 3.00 X .9 ...

oTin' — 11 cents per milligram.

When a long narrow deposit is being sampled, such as bars along a river, rows of holes are often drilled acrass the bars at distances of 1000 feet along the river. Holes in the rows are often about 150 feet apart. Whenever erratic occurence of gold in the bars is found, the spacing should be changed to suit local conditions. WTien the spacing of holes is irregular, the average value per cubic yard of the whole bar is found by weighting the value found in each hole by the area represented. The area between adjacent holes is multiplied by the average value in cents

Plaokr Minixg For Gold In California

[Bull. 135

il liii|i

s. I

m n

-j' O !0 O

s -

ous;

SSc

c E

If IliiJ

gSS8

(N M — o d —

s s

s §

— >OiO

:g';2gsr!gs

Ss

uso tx.So u.

o

sir

Sec. Til] SAMPLING 225

per cubic yard for tlie two holes. This is continued across the line of lioles and the two columns of fifjures representing: areas and areas timas cents per cubic yard are added. Total of the last column divided by total area jives the avera<ie value per cubic yard of the line of holes. Allow- ance nuiy be nuule for small areas to be worked beyond the last holes at either end of the row. If the gold value of the holes is decreasing rapidly toward the ends of the row, this small area will be assigned a suitable fraction of the value per cubic yard of the last hole in the row. Allowance must be made for rising bedrock at the point where the bottom of the dredge would strike it; also for a foot of barren badrock to be excavated by the dredge.

For the constant 0.3068 in the denominator of the above formula, some engineers have substituted the quantity 0.27, because the sampling done by drills usually gives a figure that is too low for the value per cubic yard of the gravel. Other engineers wish to discount their results, and substitute 0.8333 for 0.3068. Such substitution is bad practice because it causes confusion. If the engineer feels that his figures should be increased or decreased for any reason, he should state the reason and the percentage of increase or decrease. In all cases he should report the actual number of milligrams of gold recovered from the hole.

A log-sheet for such a drilling job contains 11 columns, and an entry is made in each column every time the casing is driven a foot. Column no. 1 is an entry of the total depth to which casing has been driven in feet and tenths of a foot ; column no. 2 is the length of core after driving (length of casing minus length of tools and cable below top of casing with tools resting on top of core) ; column no. 3 is length of core in casing after drilling (about 0.3 feet) ; column no. 4 is length of core after pumping ; column no. 5 is actual depth of hole to top of core ; column no. 6 is an estimate of the number of milligrams of gold and is divided into three sub-columns; (a) milligrams of gold in particles over 7 milligrams in weight, (b) milligrams of gold in particles 2 milligrams to 7 milligrams in weight, (c) milligrams of gold in particles less than 2 milligrams in weight; column no. 7 is an estimate of amount of gravel caught in pan expressed in units of 'panfulls' (normally 0.75) ; column no. 8 is time of day at which pumping was finished ; column no. 9 is a description of the firmness of the gravel (loose, firm, or very firm) ; column no. 10 is type of material (soil, clay, cemented gravel, fine gravel, medium gravel, coarse gravel, or large boulders) ; column no. 11 is remarks (occurrence of some unusual mineral, rusty gold, change in character of gold, causes of delays, or anything else important or unusual).

Gardner and Johnson have published a table of drilling results compared with actual recovery by dredging on 40 different tracts of land. On 23 of the tracts recovery was more than 100 percent of the gold con- tent indicated by the drill-sampling, on 16 tracts recovery was less than 100 percent, and on one tract, recovery was practically 100 percent. When recovery is less than 100 percent, the dredge may have left some of the gold behind. This is practically unavoidable where bedrock is very hard, and contains cracks and fissures into which the gold can settle beyond reach. No satisfactory method has yet been devised for accu- rately calculating percentage recovery by a dredge. However, when

3 Op. cit, pp. 42-45.

22C) i'i.A( i:i{ Aii.\i.\<; iok ( Ar.iioKNrA [liiill. l;).")

i-fcovcry is iiinrc tliaii 1(U percfiil, it can iiicaii only tliat saiiipliii- rt'siilts wore low. 'i'lic majority ol" oases iiiciil ioii(><l above fall iiilo lliis class. Shafts that have been sunk arouiul drill holes have indicated the same tiling; recovery of fiold ])ei- cnhic >ard from the shaft has been ;:i-eater than that from the drill-hole.

]{es\d1s of drill-saiiiplinji- are likely to be low in loose <;ravel as tailinr, because of poor eoi'e-recovei-y. Drivinjr the casin}J: will push some of the i-avel aside, and tlie bit of the drill will |)ush moi-e of it. aside. The sand-pinna is used as much as possible after the casinj- is driven and befoi-e drilling' is started. However, some of the ri'Mvej is usually too lai'Lic 1o pick up with tlie i)uni|). and the bit must be iiseil to break it up.

Table 1 and the following' (piotation ai'( reproduced from . S. ]>nreau of .Mines Information Circular ()7S() by (larduer ami .lohnsou."*

'I'lic iiri.s|ic(l iii;r was carried to a conclusion in i-;ich iiistnncc. I)n-(l;;in' ful- lowrd I 111- inDsin'ciin;; in f<inr fif the .six cases.

'I'lir l.ir;;.' .iitlVirncr in c.st <ii cnuinrcrin;; li.-lwern .i..l.s 1 and no. -J was <lnr lo liic nmcli lar.-r ovcrln'ad at L' on account of tin- nature of tlie (leposil. Tiie

distance from liead.jnarters at S.ui Francisco also .ilTecied tin- size of the en;i rin

fon-e necess.-ii'.v <ni the ronnil. .Jo!) no. '.', was in effect two jolis. Tile w..rl< was inleirnpted for a full year.

'Mol, no. 4 was favored l.y :in .iniple force of experience.! ;;ra\<'l miners, .-i |..w w.iter le\el. and no! a dilli.ull (inantity to liandle. 1 >iapliraf;ni hi\iH' pumps wen- used :ind in some siiafls In., d.-ep for sucti.m. a s.'coiid sliaft sunl< 10 f.-et d.'<"p and a.ljacenr to tiie first was used for increasing; the effective deptii, i.y means of two lifts.

'.Foil no. ."( was a very diflicult undertaUiiiK required llie use of steel tele- scoping' caissons, esiiecially di'si<;ned for the joh. (Jasolini'-driven pumps of the jack- iie.id deep-well cylinder proved vi'ry awkward liut most effective.

liotli .i<.l.s no. 4 and no. .". the total contents of the sli:ifts were washed in a lon-tom device hy hand and in jol. no. 4 a check samiile was cut from (he side of the shaft and washed in a rocker.

"Joli no. is a typical c:ise of shaft prosiiectiiis in frozen ground when- the 'ravel deposit is unusually thin or shallow. Here (he conditions for shaft work were very favorable, hut (he hi;;h cos( of li\ in' was reflected in (ho unit cost. Where experienced men are available, as in this case. ;ind ecpiipnn-nt developed by the miners for inacces- sible places is at hand tln-ir use. a very low unit cos( is obtained.

"Drilliii};: in fro/.en ground is also very economical, owinu to the sjieed w iiii which the work is accomplislie<l .-md the absence of casing' costs. The volume of sample is (piickly ami accurately obtained Ity water measurement after completion of the hole.

"The unit cost or cost per foot for placi-r pros|iectin' is usually uncertain, since il depends upon the total foota;ie. The nuinlier of holes or cross sections as the case reipiires may prove to be very few, and the total cost of slartin;; and clearing up the job falls uiion a small total footar'. Two c.ises can be cited as follows: One in Colombia, S. A., cost about $L'."),000 for about 1 ,r)00 feet of drilling where the equipment was left behind and never salvaged. Another in c<'nlral Alaska cost about the' same for less than .".(M) feet of drilling where the e(iuipment was not .salvaged on account of cost. In such cases and in many others that constandy arise costs can be reduced to a very low lifjiire by a preliminary e.\aniina(ion made by an experienced and reliable placer- mining engineer and are usually repre.sen(ed by (he engineer's fee and expenses. The number and distribudon of i)rospec( holes needed to piovide (he essential information <-an bo readily determined by the i)re|imin.ir.\ survey."

1 Op. (it., p. ::

Geophysical Prospecting

Geophysical inetliods liavo been used to a limited extent for tracing buried river channels containing' gravel (lei)osits. Such methods must be used iu connection with a caixd'ul study of the local geolopy ; other- wise interpretation of the i-esults will be impossible. (ie()i)hysical methods may infoi-mation about the coui'se and the depth of the channel, but they tell noth.in- whatever about the jiold-content of the gravel. This must be detei-miued by one of the sampling methods described above.

Magnetic methods may be used where the gravel has either a higher or a lower magnetic ])ermeability than the underlying bedrock. How- ever, if a lava capping exists over the gravel magnetic conditions in this may interfere so much that the method cannot be applied. If the gravel contains concentrations of magnetite-sand, a magnetic survey will reveal magnetic 'highs'. On the other hand, if the bedrock is more magnetic than the gravel, the channel may be outlined by observing the magnetic 'lows' above it. Ellsworth describes such a survey made of a channel, of which the position had already been determined by mine-workings, at Forest Hill Divide, California. The instrument used was the Hotchkiss Superdip magnetometer.

The U. S. Bureau of Mines was developing a method of tracing buried river cliannels by resistivity measurements before the war. This method shows promise of considerable success, but those in charge of the work have not yet been able to put the results in report-form because of the search for strategic minerals after the war started.

A channel located in California has been outlined by a large geophysical engineering company with seismic work by the refraction method. The results were later confirmed in part by drilling. Although officials of the company which did this work feel that the method possesses merit, they do not want to report on it because results obtained by them have not yet been checked by actual mining.

Some results of geophysical surveys at the Koseoe Placer of Humphreys Gold Corporation in Colorado have been described by Dart Wantland.- Both resistivity and magnetic methods were used.

1 Ellsworth, E. \V., Tracing: buried river channel depo.sit.s by geomagnetic method.s : California .lour. Mines and (Jeology. vol. 2H, pp. 244-250, 1933.

- Wantland, Dart, A coinparisoii of geophysical surveys and the results of opera- tions at the Ro.scoe Placer of the Humphreys Cold Corporation, Jefferson Cnmity, Coloradcj : Colorado School of Mines Quart., vol. .'2, no. 1 , January 1 9:57.

(227)

Section Iv

Placer Mines By Counties

111 the following' pages are listed ]n-operties which have been operated recently, or which tire tlioiigiit to contain reserves of placer- gravel. They are to be regarded as examples only; more complete lists will be found in reports on individual counties contained in onr Cali- fornia Journal of ]\Iines and Geology.

The California State Division of Mines does not sample placer mines. This involves a campaign of drilling or one of the other methods described herein in Section 111, Prospecihuj and Scnnpling Placer Deposits, and the Division of Mines is not equipped to do this work. Any statements contained liei-ein regarding the amount of gold in placer gravels have been obtained from jcrsons not connected with the Division of Mines, but oidy figures that are believed to be reliable have been used. Readers should not invest m(>n(\A- in e(|nip])ing or purchasing placer mines on the basis of these figures. The value of deposits should be checked by a competent engineer using the methods described in Section III before an investment is made.

Figures on the production of certain operations are given below. Such statistics are collected by the W S. lureau of Klines ami have been compiled by Merrill.

All but a few of California's gold mines were shut down late in 19-2 by Limitation Order Ti-2()8 of the AVar Production Board, which remained in effect until Julv 1, 1045.

1 Merrill, C. \V., and Gaylord, H. ]M., Clold, silver, cii)i)er, lead, and zinc in California (Mine Report) : U. S. Bur. Mine.s Mineral.s Vearlxioks, 1;M0 to 1U4.;.

( I'-Xj )

ri,.\(i:i.' I'ok- cdi.i. ( Ai.iioHMA [r.iill.]:{5

Sec. IV] MINKS T5Y COUNTIES 231

Amador County

All< n Rdncli. Iloiiry and AVcavor operated a drajrline dred<,'e on llie Allen Kancli })r()i)erty on Sutter Creek (iuleh during part of 1041. The (lrailine exeavat(r Avas equipped Avitli a -(Mil)ic yard bucket.

.{)n<idor Drcdghu/ (U))np(ii}y, Tone, operated a dragline dredge in tlie lone district during 1941.

Arroyo Scco Gold /irif/ Compainf, .'{51 California Street, San Fi-ancisco, operated an ele('tri(; connected-bucket dredge, eipiipped with eighty-six 6-cu.ft. buckets from January 1 to May 1"), ]94]. The company ojiei-ated throughout 1040 also at a property 3 miles west of [one.

J)( I'Jslafr. Mountain Gold /ing Conipauy of Plymouth and AV. 1). Ingram operated dragline dredges on this property near J*lymouth during 1941.

Ingram ojierated also on Indian Creek 4 miles west of Plymouth with two dragline excavators equipped with 25-cu.yd. and l-cu.yd. Inickets. Land was restored for agricultural use by leveling tailing and i'e]ilacing overburden.

Elephant Hydraulic Mine. This mine, near Volcano, was operated in 1932 by the K. D. Winship estate. One and one-half to 3 feet of gravel on decomposed slate bedrock are overlain by 40 to 4.3 feet of volcanic ash. AVater amounting to 13.') miner's inches was delivered to one no. 2 giant through 18-inch and 8-inch pipe-lines under 11.") feet of head. CJold was recovered in a sluice 18 inches wide, 16 inches deep and 32 feet long, erpiipped with Hungarian riffles. Two men whose wages were .'f3..")0 per 9-hour shift washed 3G00 cubic yards during a 90-day season at a total cost of .$0.20 ])er cubic yard for labor and supplies. The volcanic ash was drilled with hand augers, blasted and piped through the sluice. Cravel was tight but was cut by the giant. Bywash-water amounting to 40 miner's inches raised the total through the sluice to 17.1 inches.

Garibaldi Mine. Caribaldi Bros., of Volcano operated a nonfloating washing plant, to which gravel was delivered by mechanical means, at their mine on Pioneer Creek half a mile east of Volcano, intermittently during 1941. The yield from 33.200 cubic yards of gravel was 229 ounces of gold and 3.") ounces of silver. This mine was worked during parts of 1940 also. Garibaldi or Boardman property was operated by dragline and dry-land dredging in 1942. The dragline dredge recovered 775 ounces of gold and 102 ounces of silver from 172,200 cubic yards of gravel, and the drA'-land dredge recovered 157 ounces of gold and 23 ounces of silver from 35,500 cubic yards of gravel.

Horfieshoe Dredginy Company, Tone, operated a dragline dredge in the lone district from May 2 until July 26, 1940.

Horton Mine. This mine is in Jackson Valley 5 miles south of Tone and was operated by H. C4. Kreth of Tone by hydraulicking from January to June and from October to December, 1941.

Independenee Gold Mi7ies. This company treated 12,100 cubic yards of gravel in the Camanche district at a stationary wa.shing plant between July 30 and October 12, 1941, recovering 187 ounces of gold and 19 ounces of silver.

232 I'LACKK MINING I(K COLO IN (Ar.IFORMA [Bull.l3o

Irish Hill Minr. :\rcQuP('n and I)o\viiiii<r, 1040 :tll Street. Sacra- iiionto, ojicrated a drajrliiio dredge at tliis mine from March 28 to June 2r,J041.

Kent Proinrhi. Diiriiifr 1040. E. A. Kent, 7)1 California Street, San Francisco, opei'atcd two drajrline di'('d<i:e.s on Sutter Creek between the towns of Sutter Creek and Volcano. One was equipped with a l:",- eu.yd. bucket, the other with a 2!-cu.yd. bucket.

Lanchd Plana (ioUl J)r((h/i)i(/ Compaiij/, La Lomita liancho, Locke- ford, operated an (decti'ic connected-bucket dredjic, eciuipped with sixty- five 42-cu.ft. buck(>ts on Jackson Creek near I'uena \'ista throu<;hout lf)40 Jind from January 1 to .May 1!I41. wlicn it was di.smantled and moved to l.utte Count\'.

Jjorcntz Propcrhi. Lurcnl/ and Swiniile and Loinj liar Gold - iiu/ (ompanji operated dra'line drcdu'es on this propri'ty on tlie Cosum- nes Kiv(M- in 1!*42. 'J'hc company i-ecovered 1140 ounces of <roKl and 13S ounces of silver from 200.000 cubic \ards of i-avel. Lorentz and Swing;le also operated on Cosumncs Kivei-. 7 miles luirthwest of Plymouth in 1941.

Mainlich Prt/jx rhi. Moinitnin dohl /infi Cdinixinn of Plym- outh operated a di-aline di- at this pi-ojierty neai- Diytown inter- mittently durin<r lf)41.

Mcdulloh Prujx rhi. I'ncijic Placers Engiticcriiuj f'onipanji, 3400 H Street, Sacramento, operated a drapline dred<re on this property in the lone district durinjr jjarts of 1!)40 and 1941. Yield from 350,000 cubic yar<ls of <.rravel was 274f) ounces of <rold and 258 ounces of silver in 1!)41.

Pension Mine. Lone/ liar Gold /inf} Conipanjf, 935 Forum IJuildiufr, Sacramento, operated a drajline dredj>e at this mine from Sep- tember 13 to 28, 1942. A volume of 14,000 cubic yards of <rravel yielded 87 ounces of gold and 12 ounces of silver.

Placrritas Mini)i<j (onijxinn, 245 North (ii-ainercy Place, Lo.s Anjreles, operated a di-agline di-edjre on six ditferent properties in 1940, all within a radius of 4 miles from T*lymouth.

Rim Cam Gold J)r( (h/inf/ Ctunpinni operated a (li-a<rline di-edj:e on two l)ropei-ties near T)i-yto\vn and on the Cosunnies Kiver between Plymouth and Xashville in 1!>40. (See also Ya<nr Ranch.)

River Pine Mining Comjxinn. This company, address of which was Plymouth, opei-ated a drajiline di-edge near Aukum, whieh was equipped with a l''-cu.yd. bucket, from January 1 to June 12, 1941, when, it was moved to El Doi-ado County. The yield from 300,000 cubic yards of i-avel was 1380 ouiu*es of jrold a)ul 192 ounces of silvei- in 1941. This was the most productive drajrline dredjre in the county in 1940.

Rupleif Ranch. This property is on Willow Creek 5 miles west of Drytown. J. Pantle operated a dry-land dredfje here from January 1 to October 15, 1942. He recovered 1290 ounces of jrold and 183 ounces of silver fi-om 230,000 cubic yai'ds of jrravel. A (lraj>line 'excavator ef|uipped with a l.l-cu.yd. bucket (hdivered {Travel to the washinji: i)lant. Tlie yield in 1941 was 1850 ounces of jrold and 254 ounces of silver from :;(i(),000 cubic yards of prravel. In 1940. Pantle 's recovery from 205,000 cubic yards of <;ravel was 1154 ouiu-es of trold and 139 ounces of silver.

San Andreas Gold Dredf/inf/ Company, 960 Russ Building, San Francisco, operated a dragline dredge with H-cu.yd. bucket on the Arroyo Seco Ranch during part of 1940.

Sec. IV] MINES BY COUNTIES 233

Treble Clef Mine. E. L. Lilly, 706 California Building, Stockton, operated a dragline dredge with 21-cn.yd. bucket during parts of 1941. The outfit Avas operated throughout lf)40 on two different properties.

Yiujcr lidnrh. Rim Cam Gold Dycdf/iitfi Compan]) operated a drag- line dredge on tliis propei-tv in the Tone disti-iet from February 4 to May 26, 1941.

Butte County

A number of drift mines in Butte County such as the Ennna, Indian Sjirings, and Perschbaker were ver}- productive years ago, but drift mining has not been active in the county recently. Segments of the iniderground channels renmin un worked, but prospecting, development- work, and sampling are needed to determine whether they can be worked at a profit. Further details are given by Logan and Lindgren. Recent l)r()duL'ti()n of the county has been mostly from dredging. The principal producers of placer gold from 1940 to 1943 are mentioned below.

Amo mine in Oroville district was operated in 1942 by F. C. Peter- son, Box 550, Oroville, who used a non-floating washing plant and recovered 379 ounces of gold and 12 ounces of silver from 60,000 cubic yards of gravel.

Baker and McCowan, Palermo, operated a dragline dredge on the Farnan Ranch in the Oroville district in 1940.

Butte Operatinrj Company, Oroville, operated a dragline dredge in the Oroville district throughout 1940.

Conj and Strong Placer is 2.8 miles by road north of Stirling City and contains 320 acres in the Ei .sec. 16, t! 24 X., R. 4 E., M. D., on the west side of West Branch of Feather River. A large lava-covered trough, locally known as the Mammoth Channel, crosses the property. Bedrock rims are 1500 to 2000 feet apart. Years ago, an adit was driven at a point 400 feet south of the north property-line to a length of 700 feet. It is in lava-wash supposed to be higher than the main channel but George E. Strong of Dixon, California, states that it produced enough gold to pay for the work.

Strong says that a shaft, which was kept nn watered by a 3-inch pump was sunk on the bank of the river, and that a drill-hole was put down 454 feet from the bottom of the shaft in sand and clay to reach hard bedrock. He is planning some more drilling in an effort to locate gravel containing gold in paying amounts.

Gold Hill Dredging Company, 311 California Street, San Fran- cisco, operated a connected-bucket dredge with seventy-four 9-cu.ft. buckets on the Wilton Kister property, on the east side of Feather River 7 miles south of Oroville during 1940, 1941, 1942.

Golden Feather Dredging Company, 817 25th Street, Sacramento, operated a dragline dredge, using a 5-cu.yd. bucket, on the Feather River opposite the town of Oroville from February 1940 until late in 1944. This operation was given a special permit by the War Production

1 Log-an, C. A., Butte County: California Div. Mines, Mining in California, State Mineralogisf.s Rept. 26, pp. 383-40G, 1930.

Logan, r. A., Butte-Countv : California Jour. Mines and Geology, vol. 31, p. 6, 193.T.

2 Lindgren, W"aldemar, The Tertiarv gravel.s of the Sierra Nevada of California: U. S. Geol. Survey Prof. Paper 73, pp. S4-&3, 1911.

234 I'LAfiiR :\ii\ix(; for com) in cAr.ii'ORXiA [ I'.iill. l:!.")

H(tar(l hpcaiisc jri-avel was cltarod from tlic Fcathor TJivcr cliaiiiu'l and stacked a.s a Icvoo to protect tlie town of Orovillo. Furtlier details liavc boon puhlisbod by Wiltsee."'

Unin})hrciifi Gold Corporation, 010 First National Rank P>uildinr, Denver, Colorado, operated a dry-land drod<re on tlie T.. T. Ivister i)rop- erty, Oroville district, duriiifr part of 1040.

Jiitrrstnfr fincfi, Inc., Ohieo, moved a di-aline from 'I'l-init.v Connty to tlie Cianella "Ranch. Oj-oville district, and operated it during part of 1040 and 1041.

Knufuhl (171(1 T)(ni{so)i, Oroville, worked tbe Foi-d ])i-operty dnrinj,' part of 1041. The excavator used a 1-eu.yd. bucket.

Pinna Cold Drrdfjiiu/ Company, La Tiomita Rancho, Tioeke- ford, moved its eonnected-bneket dredge from Amadoi" County to the l>utte Creek district, resumed operations iu October 1041, and worked until October 12, 1042. The dred<e had .sixty-five 4cu.ft. buckets.

T.cmroh Mininrj Company, 2401 Bayshore Boulevard, San Fran- ci.sco. operated a drajrline dredire in the Nfajralia district durinji' i)art of 1040. In 1041, this company operated a dragline dredtre u.sin<r a 2cu.- yd. bucket; 504,848 cubic yards of g:ravel yielded 2730 ounces of old and lOo ounces of silver.

Lord and Bishop (Lohicasa Company after January 1. 1041 ). Box 812. Sacramento, washed 66,300 cubic yards of jrravel by draiiine dredjiiji<r in the Oroville district durinpr part of 1040 and recovei-ed 336 ounces of 'old and 11 "ounces of silver. The dragline excavator had a 1 .]- cu.vd. bucket. Tn 1041, Lobicasa Company operated on the Peters Ranch.

Morris Ravine Mining Company, Oroville, operated a drift mine in the Oroville district in 1042 and recovered 6r)8 ounces of old and 65 ounces of .silver from 850 cubic yards of gravel. This mine was worked in 1043 also.

Oroville Cold Dredging Company, 2052 Bird Street, Oroville, operated a connected-bucket dredge with seventy-two 8.1-eu.ft. buckets on the Ilazelbusch and T. Rogers tracts on Featlier Rivei- 0 miles southwest of Oroville during 1041 and part of 1043.

Piedmont Dredging Company operated a Becker-IIopkins type dredge on Butte Creek during part of 1041. Recovery from 20,502 cid)ic yards of gravel was 121 ounces of gold aiul 10 ounces of silver.

Piomho Bros, tf; Company, 1517 Turk Street, San Francisco, oper- ated a dragline dredge, using a l.-cu.vd. bucket, on French Creek throughout 1040 and 1041.

Placer Development Company, 2401 Bayshore Boulevard. San Francisco, operated a dragline dredge in the Oroville district during l>art of 1040, and at Meadows 3 miles south of Oroville in 1041. The dragline excavator used a bucket of 2i-cubic yards.

Placer Exploration Company, Box 408, Chico, operated two drag- line di-edges in the Oroville district in 1041. One was equipped with a 5-Md>ic yard bucket, the other with a 2J-cubic yard bucket. Several l)roperties were worked including the following: Dagorret, California Tjands, Inc., and Innis. In 1041, this company worked on the Gianella

Wlltsee, E. A., Operations of Golden Feather Dredging Company: Min. Cong. Jour., pp. 21-24, 35, August 1944.

Sec. IV] MINES HY COUNTIES 235

Ranch;- also dnrinp: part of 1942. The Tunis Ranch was worked in 1942 also.

William Richer tO Sois, Oroville, operated a dra<?line dredge on the Douglas Jacob, Mary ITarrin, V. Gamble, and John Bilkli prop- erties in the Oroville district in 1940. They worked on the following properties in Oroville district in 1941 : Belkriet, Bilkli. Freidel, Helen Whittier, Hume and Coleman, John Aim, Lorrie, Ray Angle, Rottinger, and Wyandotte.

Su7imar Dredging Company, Box 228," Oroville, operated a drag- line dredge in Weymans Ravine 4 miles from Oroville during part of 1940. The dragline excavator used a 2-cubic yard bucket. In 1941 this company used e(iuipment with IJ-cubic yard bucket on the following properties : Clark, Cratt, Schwartz, Crowder and Binney, Darby, Darby ynd Crowder, Leal, and Schwartz and Pedrazzini properties. This company worked on the Gianella and Peter properties in 1942.

Yiiha Consolidated Gold Fields, 351 California Street, San Fran- cisco, operated four electric connected-bucket dredges in the Oroville district during the 4-year period under consideration until October 15, 1942. Bucket-lines were as folloM's: eighty-four 9-cubic foot buckets, eighty-nine 9-cubic foot buckets, eighty-seven 9-cubic foot buckets, and seventy-one 6-cubic foot buckets.

Calaveras County

The drift mines of Calaveras County are of outstanding interest although all other types of placer mines have been operated in the county, and dredges have been very productive. For further informa- tion on .such operations the reader is referred to State Mineralogist's Report XXXII which contains descriptions of many mines and a long table of references to descriptions of older operations. Maps showing the ancient channel system at Mokelumne Hill, San Andreas, Angels Camp, and Vallecito are included in this report, and are sold separately by the Division of Mines. Considerable detailed information on these channels is contained in Bulletin 413 of the U. S. Bureau of Mines. Descriptions of the Vallecito-Western and Calaveras Central mines are reprinted herein because they show recent trends in the mechanization of drift mines. The need for extensive preliminary work to prepare such a mine for the production of a large tonnage per day is clearly indicated. The principal channels in this county are at a lower eleva- tion than the present surface and are reached by shafts.

Calaveras Central Mine

The Calaveras Central mine is of especial interest because it is the largest drift mine in California, and its management has pioneered in the application of more recent and more effective engineering methods to produce large tonnage at low cost. The results so far achieved, with

1 Logan, C. A., and Franke, H., Mines and mineral resources of Calaveras County : California Jour. Mines and Geology, vol. 32, pp. 324-364, 1936.

2 Julihn, C. E., and Horton, F. W., Mineral industries survey of the United States; California, Calaveras County, Mother Lode District (south). Mines of the Southern Mother Lode Region, Part I, Calaveras County: U. S. Bur. Mines Bull. 413, pp. 21-94,

Julihn, C. E. and Horton, F. W, op. cit.

236 I'LACKR MINIXC. VOK COLD IN' CAMFORNIA [BuU. 135

imicli yet n'lnaiiiiii' to Ix- done in the (Icvelopinent of improved prac- tice, at least jioiiit tlie way toward the only course likely to revitalize drift niinin<r. wliich lias so lonr been moribund. Tbey demonstrate that reasonably lare, steady production attained thro\i<rh increased mechani- zation, similar to that already in use in many lode mines, is highly effec- tive in reduciufr the costs of drift mininpr as well.

The mine is about 1 mile north of An<,'els Camp, it is ojjcrated by the Calaveras Central (Jold :\Iininjr Co.. Ltd., TOo llobart Jiuild- in<r, San Francisco. The data in re<:ard to these ojierations were made available for .study by Harry Sears, iresident and Mieral man- ajrer, from records of his company.

The company is said to control, by ]on<r-tci-iii leases, 870 coiitijxiious acres, extendin<r about .'U miles aloufr the Central Hill Channel of the main Tertiary Calaveras River, in sees. 21, 22, 23, 2(), 27, and 2S, T. 3 X., 13 E. This includes mining ri- in areas foi-nuM-ly controlled by the Victor, McElroy, Pierano, and Reiner mines, the E. W. .lohnson ranch, the Slab Ranch, and other mines (f the Calmo Minin<i- & Miliin<r Co.

History and Production

The first recorded development on this ])roperty occui-red before 18()6. when the McElroy shaft was sunk on an intervolcanic channel called by the same name. This shaft, ])erhaps one of the first in Cali- fornia to be sunk in an attempt to mine deep gravels by svu'h means, was about 200 feet deep. It was equipped with a hoist operated by a primi- tive overshot water wheel. It penetrated rich jrravel, but after about $100,000 had been produced from a short distance along- the chainiel, operations were stopped by floodin<r.

About 1866 the Mattison shaft was jiartly sunk on T.ald Hill, the site of the present hoist and com])i-essor buildings, and in the bottom pravels of that shaft the much publicized Calavei-as skull, that ])roved to be a hoax, was alleged to have been found. Other desultory attempts to reach and work the gravels of the area continued but accomilished little, and production amounted to only about 2000 ounces of gold from 1000 to June 1031, when the present company began operations from a previously existing three-compartment shaft 3r)0 feet deep. Since then it is said to have produced 20,000 oinices of gold, bringing the total production during the present century to 22,000 ounces.

The Gravels and Channels

The Tertiary system of gravels is well -re presented by the' various chaiuiels within the boundaries of the property, ranging from a system of at least three prevolcanic channels in the bedrock to later super- imposed intervolcanic channels, and so up to recent gravels, which ai-e present at many places on the surface. Most of these surface gravels contain a little gold, and the richer ones were worked in early years. They have, of course, no relation to the deep jiay gravels of the ancient channels, which are buried beneath 250 to 350 feet of rhyolitic and andesitic tuffs, intercalated with beds of gravel, all of which are said to carry some gold.

Just east of Slab Ranch the bedrock rims outlining the Tertiary valley in which the ancient river flowed are less than 500 feet apart, but the valley widens rapidly downstream, and a mile below this narrow neck it is more than one-half mile wide and forms a considerable basin.

Sec. IV] MINES BY COUNTIES 237

At Slab Ranch the old river flowed due west, but on entering the basin it coursed northwesterly and in turning cut several distinct channels separated by bedrock ridges or islands. Three bedrock channels in the basin have already been partly explored, but there is at least one other channel that lies somewhere in the deeper ground to the northeast that has not yet been reached. The southwest or Aetna Channel is unquestionably the yoinigest of the three, as it has cut through both the otliers. Similarly, Central Hill Channel, on which the main shaft is situated, is younger than No. 5 Channel, which it has cut through both to the southeast and northwest. Although the local relationships of these three channels are known, more exploratory work must be done, par- ticularly on the channels to the east, before they can be definitely cor- related with each other and with the main channel of the ancient river. There is evidence that Aetna Channel is not one of the main-stream channels but that it entered the basin through a gap in the rimrock to the south. Its gravels differ considerably from those in the other channels and contain a greater proportion of quartz sand and boulders. Its gold is relatively small and for the most part little worn, numerous pieces with quartz matrix adhering to them indicating that the gold has not traveled far from its source. On the contrary, in Central Hill Channel the gold is large and well worn. Nuggets weighing 1 penny- weight to 1 or 2 ounces occur frequently and the gold is identical in character with that from the Vallecito-Western and Golden River mines upstream. There is little question, therefore, that this channel was formed by the Tertiary Calaveras River, but there is evidence that it may not have been its original or main channel. In No. 5 Channel the gold is medium coarse and flaky and there are very few large nuggets. Further, the gravel in this channel is relatively shallow and the over- lying rhyolite tuff in some places reaches the bedrock on the benches, practically all of the gravel having been swept away. In most of these cases, however, enough gold was left in the creviced bedrock to make it worth mining. In the Aetna and Central Hill Channels the gravel is very thick, and nowhere have the workings reached the overlying vol- canic ash. In one instance the gravel of the Central Hill Channel overlaps a thin layer of volcanic ash, which caps No. .5 Channel. This not only confirms the greater age of No. 5 Channel but suggests that the undiscovered channel in the deeper ground to the northeast may have been the original channel of the main river through this basin. If this is true, it has an important economic bearing, as it is reasonable to suppose that the original channel contains the richest concentration of gold.

Superimposed above this system of bedrock channels in the basin are intervolcanic channels in rhyolite, of which little is known and of which only the McElroy has ever been worked. This channel lies above the lowest stratum of rhyolitic tuff and enters the basin from the south along the eastern edge of the Mother Lode. Presumably it derived much of its gold from the erosion of quartz veins and stringers of the Mother Lode formation, which passes through the southwestern end of the property. This section is near such famous mines as the Utica, Lightner, Angels Quartz, and Sultana, and numerous quartz stringers have been cut in running bedrock drifts, which invariably have shown values in gold ; in one instance a 4-foot vein found in the Aetna workings yielded a cut sample which assayed 0.20 ounce of gold.

238 I'LAfKIJ MINING I'OU (\()\A) IN ( AI,! FOHN lA [Ullll.!.")

Xo iiiollcii liivjis iiiviulcd this hiisiii, l)iit tlicrc were two distinct periods ill which heavy bhmkets of rhyolitic tntV.s were laid (h)Wii, aiul a third and later jx-i-iod during- which sexeral liundred i'eet of andesitic tuffs were deposited. In some ])laees the andesitic tuff.s have been eoin- ))letely or nearly lemoM'd hy erosion, while in otheivs 100 feet or more of them still remain.

The Calaveras Centi-al shaft j)asses through the followin;: .secpience of sti-ata: To feet of andesitic tuff, M.l feet of brown jiravel, !)() feet of rhyolitic tiilf, 20 feet of <;ray o;i-avel, 15 feet of rhyolitic tiitl", and GO feet of bluish <ii-ay <:ravel, which is more oi- les.s cemented by calcium car- bonate. Normally, the lower 'i or 4 feet of <>ravel within the confines (jf the channels comprises the richer i)ay. The vertical limits of the pay yi-avel, however, vary widely, and in one place on Xo. 5 Channel ood jxrouud was mined for 21 feet above bedrock. This is an exceptional instance and in most cases only the lower 4 to 6 feet of jiravel and 1 to feet of the bedrock are mined. The width of the i)ay j;ravel varies M-eatly. In No. 5 Channel it is 50 to 70 feet and in Central Hill and Aetna Channels 150 to 200 feet. The bedrock throujihout the workin-zs i.s either Calaveras slate or schist. The orijiiual grade of the bedrock channels has been altered by a gradual uplift of the country towai-d the northwest, ])robabIy caused by faulting movements. A gradual eleva- tion of the bedrock downstream has resulted.

The gravel itself is composed lai'gely of well-rounded porphyry, granite, gi-anodiorite, and considerable (puirtz. ]\Iany large boulders are found. The gold is coai-se, most of it being retained on a 10-mesli screen, and it is about HH~) fine, the imi)urity being lai-gelx- silvci'. It is associated with considerable jjyi'ite and a little black sand.

Development

Whei'i the proi)erty was taken over by the i)resent comijany there were three shafts on the tract. The thi'ee-compartment HeiiuM- shaft is ;i50 feet deep; the Aetna shaft, about !)()() feet southea.st of it, is 240 feet deep; the McP]lroy shaft, about 1200 feet southwest of the Kciner shaft, is 200 feet deep. The Reiner shaft was reconditioned to bee(mie the main Calaveras Central working shaft, the Aetna shaft being retimbered and connected undei-ground with the maiu work- ings so that it affords the emergency exit required by California law and assists materially in ventilating the mine. Although the McElroy shaft was sunk about 80 years ago, it has not caved aiul may later be retimbei-cd and used in working the McElroy channel. Connecting it with the present workings would aid greatly in their ventilation. The position of these .shafts with relation to the underground woi-kings and the channels that have been developed so far are shown in figiiies l:{ and 14.

The (irst work done by the present com])any, slai'ting in 1!:{1, was to rnii a cros.scut from the station of the main shaft 800 feet nortli- easl, with the object of reaching the original channel, which lies in this direction; but 520 feet from the .shaft No. 5 Channel was inter- .sected, carrying excellent values in fine and medium-coarse gold. Hecaiise of the lu'cessity of i)r()ducing j)i()m])tly, most of the develop- ing and mining done iluring the next 2 years was confined to this channel, which was explored for IGOO feet upstream, where it was cut off by a deci)er channel, apparently the one on which the main shaft

St'i. I\'J MINKS BY (;oi;xTiF,s 239

is situated. iv\<'iii pay gravel was roiiiul in this (U'cpt'r j,a'()Uiid, hut IK) hi-castin; was doiii', as new, h)W-levt'l, hedrock haida<iP tunnels must be driven before this ai-ea can be mined economieally.

From ]"J34 to inelusive, most mining' and development were oil the Central Hill Channel, which was followed downstream 2700 feet from the shaft. About ].')()() feet from the shaft this channel was ( nt throu<.ih by the Aetna Channel, the discovery of which at this intersection lias assisted materially in establishing- its position and bedrock jrade and ])roves that it can be i-cached by crosscuts to the southwest from the workings on the Central Hill Channel, thus opening it for mining at many ditiferent places and ovei- a considerable distance. Development has been confined to the three channels mentioned, which have been opened for a ma.ximum length of over 4000 feet ; but, owing to the large number of cross(;uts and parallel drifts, total development ai)i)roximates 3(),()00 feet. The total length of the three channels opened is estimated in a recent report to comprise only about one-tenth of the entire length (f channels in the property, and only a small part of the gravel in the developed portion has been mined, with the previously stated yield of 2(),()()() ounces of gold.

The company has not yet started operations on the area obtained trom tiie Calmo Mining & Milling Co., later called ]Mound City Gold .Mines, Inc., but two shafts were sunk previously. One of them, the Slab kancli shaft, was sunk in a narrow gorge where the rimrocks were only about 500 feet apart at the surface. The negative results should have been foreseen, as retention of gold there should not have been expected.

The original Calmo shaft was sunk farther downstream near the north rim, and a small amount of gold, valued at about $25,000, was produced. It included a nugget weigliing 20 ounces, but this gold came from rim gravels, as the main channel appears to lie farther south in deeper ground not reached as yet.

The plans of the present company contemplate exploration of that area by proceeding upstream on the channels that may be followed from present workings in the normal course of operations. The main cro.sscut is to be extended to the northeast until it encounters the main channel, which has not been reached as yet. This channel likewise will be sought at a higher level by a crosscut from the southeast end of the pi-esent workings. The Aetna Channel Avill also be crosscut in several places and opened for mining, a number of existing drifts being connected to serve partly develoi)ed sections of the mine.

Reserves and Values of Gravel

A recent report estimates that in pi-esent workings there are 328,000 tons of high-grade gravel, averaging $5.32 a ton, and 117,000 tons of low-grade gravel, averaging $1.19 a ton, shown by present develop- ment work. These values are based upon past recovery from adjacent gravels. It can be increased in future operations b}' reducing the tailings losses, which have been excessive. The low-grade gravel is so situated that it can be mined by drag scraping at little cost, which is expected to permit some profit. These reserves, claimed as now assured, represent but a small part of the total length of the channels in the property. ]\IucR of the unexplored ground is clo.se to and will be accessible from present workings.

240 PLAfKR MINING FOR GOLD IN CALIFORNIA [Bull. 135

Tlio coinpaiiy is plamiin- to iiicrcas( its lidistiii aiul mill capacity to ;")()() tons a day, after wliicli miiiiiiu- will he expanded <ri"adiially by addition of units of nnderiiround e(|nipinent In ]irovi(le that tonnap:e. The company records show that since lliU it lias mined 185,000 tons of material, of which about 75 percent has been auriferous frravel and bedrock that have been milled, the balance beiup- waste bedrock.

Thi-ee channels so far developed in the Calaveras Central property — the Aetiui, Central, and Xo. 5 — are said to have yielded $240, $255, and $530, i-espectivelv, i)er linear foot. The averajre recovery durin<; 1935 was $5.17 per ton, and from the bjiinniuj? of operations in June lf)31 to ]n3f), inclusive, the avei'ape was $4.94 a ton. These averajres include recovei'ies from much low-jrade fjravel extracted during; exploration work, which mipht be excluded in breasting- developed reserves. The ranjje of values found varied considerably with the character and jrrade of the bedrock and the position of the pay in relation to the 'channels. Rich concentrations were occasionally found yielding an aver- ajre as hif>h as $72 per ton for a single day and $18.71 \)ev ton for an entire mouth. The rich pay streaks provided many specimens of con- solidated p-ravel in Avhich numerous small nujrfrets are plainly visible. In one speciment the nujjjrets are all flat and lie, with reference to each other, precisely like shingles on a roof. Such ricli concentrations illus- trate the effectiveness of bedrock as a riffle under some circumstances.

The yields obtained do not represent the total L'old content of tlie prravel, as considerable tailiufrs losses occurred. About 42,000 ton.s of fine tailinjrs have been ])roduced since miniuqr bepran in 1931. Of these, 12,000 tons were re-treated and yielded $1.35 per ton with incomplete recovery. It is thoujiht that the remaininn' 30,000 tons contain about $2 per ton. This would pive a gold content of $84,000 for the fine tail- inp:s, to be distributed over the total of 140,000 tons milled, pivinjr 60 cents a ton. Added to the average of $4.94 per ton recovered, $5.54 per ton is indicated as the average gold content of all gravel mined by the present company, exclusive, of course, of any lost in the coarse tailings.

Mining and Milling

The room-aud-pillar method of mining is used. Bedrock drifts, gen- erally under the rims or in the troughs of the cliaunels, are used as haulageways.

The gravel face and 1 to 3 feet of the bedrock are shot doAvn with light loads of 40-perceut dynamite. In past operations the product has been loaded into 2-ton cars largely by Eiinco-Finley loaders. Light drifters were used for drilling. The loaded muck was hauled to the shaft by storage-battery locomotives, generally in trains of four to .six cars, and dumped into a gravel jocket, from which it was drawn into 2.i-ton skips and hoisted. The skips were dumped automatically into a 70-ton mill bin adjoining the head frame. Waste was delivered to a 20-ton bin, from which it was discharged by a 200-foot stacker with a 24-incli belt.

In the milling system used for most of the past production the material in the bin was fed to a 21- by 5-foot cylindrical washer with a 10-foot puuched-plate screen section having 1-inch holes. The over- size from the waslier was piled by a 275-foot stacker having a 24-inch belt. The undersize passed through a specially designed sluice and gold trap 24 inches wide and then through a second sluice 12 inches

Sec. IV]

MINi:S RY COUNTIES

wide and 24 feet !<)n<r, lined with Ilunfrarian riffles. The discharge from tlie sluice was dewatered by a draf? classifier and conveyed to a Leahy vibratinjr screen, which made three products — plus J-inch mater- ial, which was piled by a loO-foot stacker havin<r a lO-incii belt; minus -inch but plus i-inch ; and minus i-inch. The two smaller sizes were treated in a Huelsdonk concentrator, the discharre from which was raised by a bucket elevator to a launder, which conveyed it to the fine-tailings dump.

The washing plant described is now being dismantled, as the com- pany plans to replace it with a plant of 500 to 600 tons capacity.

The present double-drum hoist has a capacity of 1,000 tons a day. Two Sullivan angle-compound compressors of 400 and 800 cubic feet capacity, respectively, supply air for drilling and the operation of com- pressed-air machinery. The mine makes about 150,000 gallons of water daily, which is pumped from the shaft sump by a 50-horsepower, Sterling vertical turbine pump into a 100,000-gallon tank on the hillside above the mill. This tank supplies ample water for milling. The property has a large change room, a blacksmith and machine shop, a first-aid building, oiifice, and other structures. The number of men employed has ranged from 30 to 70, but this number will be doubled under the contemplated expansion program. Costs

The following table shows the average daily mining and milling costs during 1933 and 1934, a period selected because of the wide range in the average daily tonnage treated. The costs given cover the mining and milling of gravel and auriferous bedrock and the mining of waste bedrock, the latter usually amounting to 25 or 30 percent of the total. The daily tonnages range from a high of 209 tons in May 1933 to a low of 41 tons in May 1934, the corresponding working costs being $1.40 and $3.04 per ton, respectively. The adverse eifect of the inverse ratio is at once apparent.

The costs given include labor, compensation insurance, power, explosives, lubricants, and salaries of the general manager and super- intendent. Depreciation, depletion, and other overhead co.sts are not included.

fiting and milling costs at the Calaveras Central mine from January 1933. to December 193'i, inclusire

Monthly

gross tonnage

Average

daily tonnage

Mining and mill- ing costs

per ton

January-.. February..

March

April

May

June

July

August

September October... November December.

3,399

3,719

5,433

5,753

4,313

3,315

3,137

2,526

$2.27

January . . . February..

March

May

June

July

August

September. October... November. December -

Average. 1933 and

1,271

ni

4,203

4,087

$1.64

pi.a(i:r mininc fok oold in rAi.ipoRXiA

IP.nll.lM.-)

Tilt' very iirciiilar i-atc of production indicates that development or equipment was inadecpiate to maintain steady production necessary for holding costs at a low level. Durinr the 2-year period 83.41!) tons of material was mined, an avera<;e of 114 tons a day, at a total cost of $ir)7,()f)9 and an averajre cost of $1.89 per ton.

Hased upon an analysis of cost details, the manafrement has esti- mated that if the output had averajred 200 tons daily, the correspond- ing' cost would have been $1.40 a ton, which was actually attained in May lf)33; that at 300 tons a day the correspondiufi cost shoidd be about $1.2") a ton; and that at ")()() tons a day about $1 mijrht be attained. The tenor of these conclusions is obviously correet. There remains, however, the question whether the larger rates of produc- tion can be maintained .steadily. If so, it would be accompanied by some lowerinj; of average grade, as low costs would naturally induce the mining of greater widths, including the low-grade gravels of the channel margins, and perhaps abandonment of all selection within the channels proper. This Avould exactly parallel the usual trend toward nonselective mining that proves inevitable in lode mines.

Even now the costs attained compare favorably with those current when drift mining was at the height of its prosperity, when much clieap labor was available. Then, under favorable conditions for mining and milling, cemented gravel was worked at a cost of from $1.73 to $3.50 a cubic yard, eciuivalent to $1.16 to $2.32 a ton."*

Character of Production

The gross tonnages do not, of course, consist entirely of pay gravel or income-producing product. A certain proportion must be bedrock waste, taken out in running approach and haulage tunnels, and the proportion of such material to the pay gravel has an important etfect.

In mining 185,000 terns of material, 75 percent was gravel and 25 percent waste. As the gross tonnage increases, the proportion of waste decreases, because in a small-tonnage operation the gravel is mined more selectively to offset high cost. To maintain this liigh average grade there must be constant additions to the main haulage system in order to pass through or around low- or even medium-grade gravel to reach the grade being mined ; but in an operation where the daily tonnage is large and the cost lower, the gravel need not be mined so st>lectively, and its bulk in proportion to waste becomes greater.

The general et!"ect of increased tonnage in reducing the percentage of waste is thought by the management to be somewhat as indicated below. For 100 and 200 tons the figures are based upon records; for the higher tonnages they are estimates as to effects that might be rea.sonably expected.

Daily production

Waste

Gravel

Pay material

lOOtons ...

Tons

Percent

200 tons

300 tons

400ton8 .

500 ions

Hammond, John Hays, The auilferou.'* gra> Min. Bur., State Mineralogi.sf.s Rept. 9, p. 119, 1889.

)f <\ilifornia: California State

Sec. IV] MIXES BY COUXTIES 243

The use of mechanical h)a(lers in this mine has been an important means of reducing: costs. To obtain from them the benefit of con- tinnous operation, empty ears always be at the face for loading. Switch si)urs are therefore driven at frequent intervals as the headings are extended, to aid in placing cars. Usually these spurs develop later into crosscuts or other haulageways. Sometimes, however, cars are lifted bodily and transferred to the end of the train by means of a device, developed at this mine, that may be called a car derrick. It consists of a 6-inch I-beam, about 9 feet long, with a l-ton, geared chain hoist on a carriage that rolls on the lower flanges of the beam. The beam is wedged securely at each end into niches cut in the walls near the roof, or it may be supported partly by .stulls. A steel spreader with hooks at each end depends from the hook of the chain hoist. The hooks are swung under either the ends or sides of the car and it is lifted a few inches off the track and pu.shed into a shallow rece.ss in the wall, far enough to clear the train. When the locomotive has pulled the train by, the empty car is returned to the track. Use of this derrick is said to save a great deal of time and expense that would be required to pre- pare switching spurs. It is especiallv useful in driving long bedrock drifts.

The great savings effected by mechanical loading underground have led the management to devise a system of mining that seeks to utilize it to the utmost. The following notes concerning this and other means of reducing costs and increasing efficiency are condensed from data furnished by Harry Sears, general manager. Technology of Drift Mining

The gravel is tightly cemented ; bedrock drifts usually hold firm without timbering, hence both gravel and bedrock are treated like hard rock of a lode mine. The mine is being laid out with the object of opening it in a number of sections with separate equipment provided for their operation. Enough of them are to be provided to assure pro- duction of the mine as a whole at a steady rate and to permit the sections to remain idle after blasting long enough for the smoke to be dispelled.

The workings are planned so as to permit good circulation of air, and many crosscuts and connecting drifts have been run for this pur- pose, which, incidentally, have served as exploration drifts. In most eases the efficiency gained through the better air conditions has largely paid for the exploration drifts.

Headings generally are 7 by 7 feet. Drifts are run on a grade of

1 percent to assure drainage away from the faces, except in very wet gravel with considerable sand, where the grade sometimes is increased to 2 percent, as otherwise the sand would settle on the tracks and too much time would be lost in keeping them clear. Normally there is 1 to

2 feet of bedrock in each gravel face, the rest of the 7 feet being gravel.

The whole of the face is drilled, usually with 8 to 10 holes 6 to 7 feet deep. Most of the headings are loaded out with mucking machines and, before shooting, the rails with slide rails in place are brought practically up to the face. The holes are loaded and shot so as to deliver the muck, combined gravel, and bedrock in a compact pile close to the face. It is therefore a simple matter to bring a loader into the heading, clean up the track, and quickly reach the main muck pile. The slide rails are advanced as needed, the lip of the loader scoop being used to push them under the muck when required.

244 PLACFR MrNINP, FOR GOM) IN CALIFORNIA fBllU. 135

Many areas have been Avorkcd by driving'' rotidily i)arallel drifts with lon' walls botweon th(Mn, these walls later beinj:- shot throu'h at refrular intervals to form pillars. This was done with the tracks in both drifts in place, and nearly all of the muck was handled with the loaders. For this work the track is laid on Hat steel ties, and it can be slid or barred over from its ori<rinal jiosition when re((nired. Con- siderinjr each of these workin<r ai-eas as a room containing: a number of pillars or walls, if it is desired to mine it out completely and retreat, this can be done by pointinjr the track at individual ])illars as they are finally sliot out. and taking- up and shorteninr the track while retreating: to the entrance of the room. Stulls with headboards or caps may be required to support the <iround while the final pillars are being .shot and loaded out. but often they are not.

The loaders have also been used on longwall work, by drillinpr the wall and sliding tlie track over almost against it so that the muck will be thrown on the ti-ack. In all of these methods a moderate amount of hand-sliovel work is necessary to clean U]i completely spots beyond the radius of the loader scoop. The best method of handling each mining area must, of course, be determined somewhat by the character of the ground.

All of the muck is loaded, and no boulders are separated or piled underground. The old practice of piling boulders underground recjuires much hand labor and is far more expensive than bringing them to the surface. Of cour.se, very large boulders must be bulldozed or broken with sledges before they can be loaded out. and occasionally some of these larger bouldei-s are left underground. l)ut never piled up as Avails. The bedrock is never scrai)ed. but is shot and treated as gravel, being taken to sufficient depth to get all the gold in its crevices.

Work with a multiple-track system not only provides several head- ings for loading in a comparatively small area, but makes it possible to maintain switches close to the faces, so that empty ears may be readily available and the loaders can be kejit in steady ojieration.

In driving long, single-track, bedrock haulage drifts by means of a car derrick, several thousand feet of drifts have been driven at the rate of 18 feet per day. with two men in each heading, three shifts per day. Each shift drilled, shot, and loaded out the muck for a ()-foot advance and did the necessary ti-ack and jiipe work. Each crew of two men. however, was assisted by a motorman who brought in the empties aind took out the loaded cars. Two-ton cars haided by storage-battery locomotives were used. The motorman 's services were only required during an api)roximate 1-hour |)eriod while mucking out. Tiravel load- ing does not generally proceed as fa.st as this, particularly with the room-and-pillar woi-k described, for considerable time is re(|uired to break large boulders, place stulls. and do track and hand-shovel work. For most rapid work, the loaders must be kept on .straight tracks for they are slowed materially when on curves. The foregoing remarks apply to the use of Eimco-Finlay loaders, which operate within a fixed radiu.s along or fr(m the end of the track, and which throw the muck back into a car that is coupled to the loader and moves with it.

A Nordberg-Butler shovel on a caterpillar tread also has been used. This shovel is very efficient in room work where a train of several cars can be delivered on the track, and the shovel can load them all without

Sec. IV] MINES BY COUNl-IES 245

spotting? or shift iiij: them. AVith its ability to move around on both sides of tlie cars and its consequent wide loading: radius, this shovel has distinct advantajres while workinj? in a prescribed area, but much more time is re(}uired to move it from place to place in the mine than with the Eimco-Finlay loaders.

In openin<r various channels and preparing multiple sections of each for production, the management endeavors to maintain independent haulage drifts, preferably beneath the lowest point of the channel troughs; or, if this cannot be done, then in the bedrock rim alongside the channel. If it is necessary to pass through the gravel itself, the drifts are kept as much as possible in low-grade gravel. With this system, entrance may be had to the channels from any required point in the haulageway and as much or as little gravel extracted as desired without impairing the efficiency or adding to the upkeep of the main haulage system. Another point of advantage is that good gravel need not be tied up indefinitely to keep the haulage drifts open.

"Where the main haulageway is deep enough below the gravel to permit it, entrance to the gravel is made through a raise and a bin is built, which can be loaded as required from the upper level and drawn when convenient by the train crew on the haulage level. Where the difference in levels is only 5 or 6 feet, transfer platforms are built to accommodate at least three cars, and these are loaded directly, either by 'center or side dumping, from the cars above. Car loading with drag scrapers is invariably done by dragging the load onto a platform beneath which a car is spotted, the load being delivered directly into the car through a slot in the platform.

Drag Scraping. A particularly interesting phase of mining at this property has been the work done with drag scrapers — probably their first use in drift mining. Though only a small tonnage has been handled by this method, it has been sufficient to establish facts on procedure and costs and its use is to be extended. The following is intended to be merely suggestive of possibilities foreseen.

In prepared ground, ninety 2-ton cars were loaded with a small scraper by three men during an 8-hour shift. It is estimated that four man-shifts were required to prepare the ground by drilling and shooting, that one man-shift was utilized for electric tramming, one-half man- shift for drawing into the skips, and one-half man-shift for hoisting, a total of nine man-shifts for drilling, shooting, loading, tramming, and hoisting 180 tons, a production of 20 tons per man-shift.

xVssuming a labor cost of $5 per man-shift, including compensation insurance, the cost delivered in the mill bin was $45. Adding one man- shift for milling and sluicing gives a total direct labor cost of $50. With an allowance of $15 for explosives, power, and incidentals, the mining and milling cost for the 180 tons handled is estimated at approximately $65, or 36 cents per ton.

It Ls thought that Avith a heavier scraper and larger cars this pro- duction could have been increased 50 percent with additional expense of two man-shifts for drilling, one-half man-shift for tramming, one-half man-shift for drawing into skips and hoisting, and one-half man-shift for milling, making an additional three and one-half man-shifts, costing $17.50. With $7.50 added for explosives, power, and incidentals, a cost of $90 for mining and milling 270 tons of gravel, or 30 cents per ton, is

246 PLACER MINING FOR GOLB IN CALIFORNIA [Bull. 135

indicated. To the foregoing costs must be added the proportion of expense properly chargeable to the ground, iiicludinfr approach and installation work. In handling: caved gravel, drilling and shooting costs are eliminated.

Unfortunately, however, the application of this method has limits, experience gained at this mine indicating that drag scraping in drift mines is suitable only for areas present ii;g certain favorable conditions of bedrock and of the gravel body itself where a large prepared tonnage can be made available. It i.s expected that this method will find its principal use in handling large toiniages of low-grade gravel, but that in many cases it can also be used for mining the high-grade gravel remain- ing after all the ground that can be mined safely by other methods has been taken out.

The preparation of ground for scraping entails considerable dead work. The gravel should first be opened and tiioroughly drained, as scraping can be done best in dry ground and water on the bedrock cau.ses a loss of gold in scraping. In dry ground more gravel is broken per shot.

For safety, the tail pulley and the tugger hoist should be placed where there is no danger from caving, and they should be accessible through drifts or raises independent of the scraping area. Tiarge scrapers and powerful tugger hoists are desirable, as the essence of suc- cess in scraping is quantity, and with heavy e(|uipment the same number of men can load a much larger tonnage than they can with light ecjuij)- ment. There should be an ample supply of both cars and locomotives, for when loading is done by this method empty cars, preferably of large capacity, must be constantly available.

Hoisting and milling capacities must be suitable for handling the large tonnage necessary for operating on low-grade gravel. Otherwise, they must be used for gravel of higher value. In future operations it is thought that a tonnage balance will be worked out between high- and low-grade gravels.

Under .some roof conditions drag scraping can best be used after the graveLis partly or largely worked out by drifting, and has then been caved or has been allowed to cave of itself to a limited lieight before scraping is attempted.

Reserve scrapers and cables must always be kept on hand, as they may be buried by caving under conditions that will prevent men from safely entering the room to recover them. Occasional losses of this equipment should be taken as a part of the cost of using the liiethod.

Project for Improvements

During forthcoming construction of a new plant, the management plans a number of fundamental changes underground as well as on the surface.

The shaft is to be entirely retimbered. new water, air. and jiower lines installed, and the shaft deepened to create a larger sump and provide additional depth for drawing from gravel and waste pockets, each to be enlarged to 100 tons capacity. A .separate gravel pocket will be provided for tonnage for sampling and testing. The bins will be arranged so that the cars on an incomiiur loaded train may be dumped into their respective pockets without disturbing the make-up of the train.

A new, 50-hor.sepower, Sterling, vertical turbine mine pump is to be installed and mounted on a roller carriage, so that when motor or

Sec. IV] MINES BY COUNTIES 247

pump repairs are necessary the complete unit may be disconnected, brou<rht to the center of one of the hoisting compartments of the shaft, hooked onto the bottom of the skip, and brou<ht to the surface.

Heavier rail will be laid throupfhont the main-haulape drifts and the track jrajie will be widened to permit the use of low-slung:, 3-ton, drop-bottom cars. Trolley locomotives will be used for main haul- age, and storage-battery locomotives in newly opened ground and for gathering and train make-up. New 3i-ton skips will be provided in the shaft for hoisting both waste and gravel, with screened cages above them for raising ancl lowering the men.

A new steel headframe 100 feet high will replace the present 65-foot wooden one. For surface storage, a 400-ton bin will be divided into three compartments — 250 tons for the regular production of gravel, 75 tons for gravel to be sampled or tested, and 75 tons for waste.

The gravel will be delivered from the bins by magnetic vibrating feeders, which will assure the regular feed essential for proper mill- ing. In order that the cemented gravel may be completely disinte- grated and the gold liberated from it. the gravel must be subjected to much attrition and scrubbing. In the old washing plant the trom- mel did not retain enough water to effect complete scrubbing of the gravel, so a watertight cylindrical washer will be installed, which will carry a much larger load than the old trommel. In this the bulk of the material will be immersed in water, and the grinding and scrubbing action of the gravel and boulders is expected to produce a much cleaner product. Breaking up the larger cemented pieces does not present as much of a problem as does material between one-sixteenth and three- eighths inch in size. The greatest loss of gold in the tailings in the past has been in this size of material in which light flakes of gold adhere to bits of gravel or light sulphides or are encased therein. It is thought that this loss may be eliminated by the increased grinding and scouring action of boulders in the new scrubber; but if it is not. this fine material will be separated by screening, to be returned for re-treatment or to be ground separately.

The coarse gold, constituting the principal part of the clean-up, will be recovered as in the past in sluices immediately following the scrubber. The sands and fines will be fed in a thin flow to Pan American jigs, which will make a rough concentrate in their hutches ; this will be cleaned by another jig to a final concentrate consisting of fine gold and black sand. This concentrate may be shipped for final recovery of its values to a plant treating black sands from dredges. The coarse material discharged from the mill will be piled by stacker belts, the fines being delivered by launders to the tailings pond.

A pilot mill will duplicate the processes of the main washing plant. Its function will be to make batch runs of 10 to 30 tons of gravel, so that any face in the mine may be separately sampled. Such large-lot sampling will determine how far mining may be profitably carried into areas of questionable value, and will serve as a constant check upon the average gold content of the mill tonnage.

Vallecito Western Drift Mine

The Vallecito Mining Company. Inc.. Murphys, worked the Val- leeito-Western drift mine throughout 1940 and recovered 221 ounces of gold and 25 ounces of silver from 685 cubic yards of gravel. The

248 PLACER MINING FOR GOLD CALIFORNLV [lUlll. 135

followiiiji' (l('Sfrij)tion of this iiiiiio is roi)riMted from V. 8. Bureau of Mines Bulletin 413.''

The \'all('eito-\Vestei'u mine is 3 miles east of An;.aMs Camp in See. 24. T. 3 N., R. 13 E. It is on the same ehannel as the Calaveras Central mine, about 2 miles dov.nstream ; and the (Jolden River mine adjoins it upstream. This is the Central Hill or main ehannel of the Tertiary Calaveras River. The property is owned by Thomas B. Bishoji Co., 1G() (Jeary Street, San Fi'aneiseo, but is luider lease to the Valle- eito Minin<i- Comi)any, of which Don Steffa, of lur])hys. California, is general manajzer. However, from Deeember l!)32 to October l!)3(i the mine was operated under sublea.se by the Tonoi)ah-r>elmont Develop- ment Comj)any under the dii-ection of Frederick Bi-adshaw. of San Francisco, and the operatiii<:- data uiven herewith cover most of this period.

Since the mine was opened in 1!'2.') it has produced over .$400, ()()() in old, reckoned at its present priccv It is develojied by a KiT-foot vertical shaft with a 4- by 4;l-foot skipway ami 2.1- by 4-foot manway. This shaft was completed in May ]!t24, its site havinu' been determined by a line of seven churn-drill holes sunk across the chaiuiel. The shaft passed throuj-h about .lO feet of white rliyolite cobble and ash and then entered a bed of well-rounded, bluish jiravel made up larjicly of jor- phyritic malei-ial ;iii(l containinii' fre(|uent beds of sand and volcanic ash. Near the Ix'drock the ])oi-phyr\- uraxel disappears, and the ]->ay gravel is largely made u]) of granite with a small i)ro])oi;tiou of (puirtz, quartzite, jasper, and slate. Pieces of chocolate-brown semipetrified wood are sometimes found in the i)ay gravels.

At a depth of l.')3 feet, a tunnel on bedrock runs upstream from the shaft station for 300 feet and then, after a vertical I'aise of o feet to surmount an abrupt rise in the bedrock, it continues on a 1 ] -percent grade for 4,000 feet. This tuuiud serves as a haulageway and drain. At the shaft the bedrock is slate, but it changes upstream first to gi-ano- diorite and then to granite cut by bauds of grauodiorite. As the grade of the bedi-ock is slightly greater than the tuuiuH grade, jiai-ticularly in its ui>stream end. the tuiuiel gradually pa.sses into the bedrock, and access to the gra\el above is gained by shoi-t raises used as chutes. The spacing of the rai.ses depends on the volume of the gi-a\el that is to be extracted through them and on the contours of the bedrock. Where the gravel is mined for widths of 100 to l.'iO fe(>t the raises may he only 50 feet ai)art. but in uari-ow workings the distance Ix-tween tlit'm ma.\- be as much as 125 feet.

The gravel is mined by bi-east stoi)iug across the full width of the paystreak. which raiiges from 40 to 150 feet and is exti-acted for an average lieight of (5 feet. Two rows of (J-foot holes, spaced 4 feet apart in th(> row. are drilled in the gi-avel faces, the lower one 1.] feet and the upper one to 4 feel above bedrock. The.se holes, loaded with three or four sticks of 40-pei-cent dynamite, bi-eak to a height of 5 feet. H" a greater height is mined, to include an occasioiud i)aystreak well above bedrock, an additioiud row of holes is drilled. (Jenerally 75 percent of the gold i-eeovered is on the bedi-ock or within a foot of it. "When the bedrock is soft or badly ci-eviced. 1 to 2 feet of it are mined. Such a eondition occurs where the bedi-ock is slate or grauodiorite, but if the pay-lead actually rests on bedivx k e\en a giauite bedi-ock is taken uj).

Juiihii, C E.. and Hurlon. F. oi'. (it.

Sec. IV] MINES BY COUNTIES 249

The gravel is well-rounded and heavy and contains many large boulders, which are piled underground in niined-out areas. Huge boulders 6 to 10 feet in niaxinuini diameter occur frequently, and these are mined around; but if they are too much in the way they are drilled and broken. Normally the gravel is not cemented but stands well. However, in some places it must be held by square-sets, though usually posts 10 to 12 feet apart, with headboards, furnish ample support.

The broken gravel is loaded at the face into wheelbarrows and dumped into the nearest chute, from which it is drawn into 1-ton ears that are hauled, in trains of four, by a storage-battery locomotive to a car dump at a point 300 feet from the shaft, where the bedrock rises abruptly. Here it is transferred to other cars trammed by hand to the shaft, where they are discharged directly into a l-ton skip.

The shaft has a 76-foot head frame Avith a built-in, -SO-ton ore bin. The skip is operated by a 50-horsepower electric hoist. An IngersoU- Rand compressor, belt-driven by a 60-horsepower motor rated at 355 cubic feet per minute, supplies air for drilling. About 100,000 gallons of water per day is pumped from the shaft .sump by a Sterling electric pump with a capacity of 135 gallons a minute. Pumping 12 to 16 hours a day handles the water.

The mine is well-ventilated. A 12-ineh churn-drill hole from the surface intersects the haulageway about 2,400 feet from the shaft and has a down draft providing fresh air. A blower .sends air from this point through 12-incli galvanized irou pipe to the tunnel face and the active mining areas.

The gold at the Vallecito-AVestern property is coarse and averages 895 fine. The balance is almost entirely silver. Ninety percent of the gold by weight stays on a 20-mesh screen. Nuggets having a value of $1 to $5 are common, and many worth from $10 to $20 have been found. The largest nugget yet discovered weighed a little less than 10 ounces.

Washiyig Plant. The washing plant adjoins the shaft. Gravel from the head-frame bin, into whit-h the .skip discharges, falls by gravity into the upper end of a sluice 12 feet long and 2 feet wide, where it is washed by only sutcient water to move rocks 4 to 5 inches in diameter. Larger rocks are picked from the .sluice by hand, thrown into a car on a lower floor, and trammed to the dump. Fifty to sixty percent of the gold is recovered in this short sluice. The finer gravel flows into a revolving washer 36 inches in diameter and 9 feet long, making 35 revolutions per minute. This washer has a 4-percent slope and is equipped with lifting plates, which elevate the gravel and then let it fall, thus breaking lumps and scouring off adhering clay. A 4-foot double trommel of punched steel plate is attached to the discharge end of the washer. The inner screen is 20 inches in diameter and has l|-inch round holes. The outer screen has one-half inch holes and is 36 inches in diameter. Plus 1-inch gravel is sluiced to the dump, but the two finer sizes are washed in separate sluices.

These sluices are 1 foot wide inside and have a 4-percent grade. They are lined with riffles of a novel design, which are very effective in preventing packing and also in retaining the gold. These riffles are of bar iron 15| inches long, 2 inches wide, and a quarter of an inch thick, bent at right angles 2 inches from each end and the bent portions beveled and drilled. The drill holes receive rivets that fasten the riffle to the

Placer Mining For Gold In California

Bull. 135

sluice liners. The bar sits at an anrle of 45° agrainst the current and its upper edge forms a lip that produces a distinct boil in the pocket beneath it. The lower edge of the riffle face does not contact the bottom of the sluice, but the intervening space fills in with small pebbles, which keep the gold from sliding along the bottom of the box.

Some loss of gold occurs in the washing plant when pieces of cemented gravel are discarded by the trommel or go through the sluices. However, relatively little cemented ground is found in the workings, and this is segregated and allowed to air-slake before it is washed.

The recovered gold averages about 0.17 ounce, or $5.95 per ton of gravel washed, but it varies, of course, within wide limits. In August 1936, 80 tons of gravel were mined and washed per 24 hours. Twenty- five men were employed on three shifts.

The following tables show the production and costs at the mine foi* a period of 45 months ended September 1, 1936. In interpreting the costs, it must be remembered that they are based on the tonnage hoisted rather than on tonnage mined. The waste hoisted was equal to 44.2 percent of the gravel milled. Most of this waste was derived from bedrock cuts, and the rest consisted of boulders which it was necessary to hoist wherever new breasts were started, until enough room was cleared to pile them back of the face. About 30 percent of the ground mined con- sisted of boulders, which were left underground, so the total waste mined approximately equaled the tonnage of gravel milled.

Costa and production of the Tallecito-Western mine, months, to September 1, 1936

Tons

Gravel mined and milled 40,967

Waste hoisted 18.102

Total gravel and waste 59.069

Value

Total

Per ton of—

Gravel

Gravel and waste

Production: Gold, 7,222.5 ounces

$232,268.00

$5.6696

$3.9321

Silver, 814.9 ounces

$232,760.00 11,713.00

$5.6816

$3.9404

Loss in tailings

$244,473.00

$5.9676

$4.1388

Corts:

Mining and milling during— Development

$62,747.05 84.111.17 14.302.64 13,344.31 13,064.07

$1.5316

$1.0623

Breastmg

Water supply

Compensation insurance

Total of direct mining and milling

$187,569.24 19.852.06

$4.5785

Indirect mining and milling

Marketing (mint charges, etc.)

Total operatmg coat

$208,593.03

$24,166.97

24,946.00

$5.0917

$.5899

Profit before payment of royalty

$.4092

Royaltiea

Urn

Sec. IV] MINES BY COUNTIES 251

The marginal character of drift mining, when conducted as described, is well-illustrated by these data of costs and production. With an aver- age gold content of $4.14 per ton of gravel and waste hoisted, which becomes $5.97 per ton for gravel alone, the actual recovery is $5.68 per ton of gravel. However, this very substantial recovery exceeds the operating cost of $5.09 per ton of gravel by only 59 cents per ton, while royalties amount to nearly 61 cents per ton, so that .there is a final loss of nearly 2 cents per ton of gravel. The net result is merely the mainte- nance through 4 years of the labor employed and payment of the royalties required by the owner of the ground, while no excess is left to reward the operating company that carried the burden of responsibilities.

The rate of production is very low, however, averaging a trifle less than 30 tons of gravel per day for the whole period. It is immediately obvious that a marginal operation at that low rate of production would probably become profitable at a higher rate of production. That, in turn, would require an additional capital investment and probably a preliminary determination of the underground contours of the channels in order to plan with certainty production adequate for profit.

Such determinations have been virtually impossible in the past because of the lack of any known method for their accomplishment except at prohibitive cost. If, however, it should prove that the buried channels of the ancient placers can be mapped completely by geophysical methods, the mining of such properties as this should no longer prove marginal but should yield substantial profits.

A portion of the gold mined during the period under consideration was marketed before its present price was attained, and the average received was $32.15 per fine ounce.

The early history and operation of this mine under the management of the Vallecito Mining Company has been described in an information circular of the Bureau of Mines.

Other Mines

Bacon, E. A., 303 Delmar Way, San Mateo, recovered 286 ounces of gold and 14 ounces of silver from 10,000 cubic yards of gravel near Wallace in 1942. Hydraulicking and a mechanical excavator were used.

Barson Mining Company, 2054 University Avenue, Berkeley, operated a dry-land dredge on the Foster Ranch in the Camanche dis- trict intermittently in 1941. Recovery from 55,200 cubic yards of gravel was 495 ounces of gold and 37 ounces of silver. (See Cat Camp Placers also.)

Calaveras Central Mine. See page 235.

Cat Camp hydraulic mine was operated by J. E. Biallas of Valley Springs in 194p. Operation of a nonfloating washing plant, for 6 months of 1941, to which gravel was delivered by a carry-all, yielded 605 ounces of gold and 34 ounces of silver from 100,000 cubic yards. In 1942, Cat Camp Placers and Burson Mining Company produced from this mine 483 ounces of gold and 32 ounces of silver from 71,818 cubic yards of gravel with nonfloating washing plants.

Steffa, Don, Gold mining and milling methods and costs at the Vallecito-Western drift mine. Angels Camp, Calif. : U.S. Bur. Mines, Inf. Circ. 6612, 14 pp., 1932.

252 PLACER MINING KOR GOLD -IN CALIFORNIA [Bull. 1.'}')

Church Union mine (Kraeiner) in see. 26, T. 5 X., U. 11 E.. M. D., is owned by J. J. McSorley and Thos. E. McSorley, Mokehinine Hill. It includes 80 acres of mineral rip:lits and :0 acres surface ri< on the same {rround, containing the Cotfee-Mill channel, which runs in an east and west direction. According: to J. J. McSorley, 20 acres of this fjround is virprin, and should yield about an ounce of <rold per cubic yard for a 6-foot cut on bedrock. A tunnel 1000 feet lonjr has been driven in bedrock beneath the channel.

Clark, U'., subleased the Val Ranch in 1942 and operated a. statioiuiry washinpr plant, to which -rravel was delivered by power .shovel and trucks. From May 7 to October 19, the yield was 69 ounces of gold and 7 ounces of silver from 6245 cubic yards of gravel.

.Deep Lead placer mine is in sec. 13, T. 5 N., R. 11 E.. M. D., and is owned by Miss Theresa Rooney, 1106 — 3rd Street. Corpus C'hri.sti, Texas, who holds 90 acres on the Chili (Julch Blue Lead chamiel. According to J. J. McSorley, Mokelumne Hill, about 20 acres of this ground remains unworked, and will yield about an ounce of gold per cubic yard for a 6-foot cut on bedrock. A shaft from 90 to 100 feet deep will be required to open the mine.

Glo-Bar Mines, 370 East 37th Street, Long B'each, operated the (Jlo- Bar drift mine in the Campo Seco district throughout 1940. Recovery from 4464 cubic yards of gravel was 321 ounces of gold and 44 ounces of silver. Operations continued in 1941.

Gold Hill Dredging Conipan}/, 311 California Street, San Fran- cisco, operated an electric connected-bucket dredge on the Arlington and Osterman [)roperties along the Mokelumne River during 5 months of

Golden Hirer Mining Conipang, Roland Rich Wooley. })resident, 915 Transamerica Building, Los Angeles, ha.s operated a mine near Vallicita in sees. 21, 29. 30, T. 3 N.. R. 14 E., M. D.. on the same main channel of the Tertiary Calaveras River on which are the Vallecito- Westem and Calaveras Central mines. This company has also done geophysical work and drilling on the adjoining Kentucky placer 2 miles northeast of Angels Camp in sees. 23, 2<), T. 3 X., R. 13 E. The Kentucky appai-ently contains a mile of virgin channel. The company was pre- paring to sink a new shaft on this projierty at the time (Oct. 8, 1942) that gold mining was shut down by Limitation Order L-208 of the "War Production Board.

, C. E., Angels Camj). opcratctl a dragline di'cdge on the Hogate ranch, miles north of Angels Camp in 1940.

Ilenrif, J. //., 740 West Willow Street, Stockton, washed 17,200 cubic yards of gravel by dragline dredging on the E. A. Marsh proi)erty 4 miles southeast of Valley Springs between May 30 and July 27, 1940, and recovered 137 ounces of gold and 13 ounces of silver. The same e<|uipment washed 45,600 cubic yards of gravel on the (Jenochio property on the Xorth Fork of the Calaveras River miles north of San Andreas between September and the end of the year; ;}62 ounces of gold and 40 ounces of silver were recovered.

Horseshoe Dredging Companij, Mokelumne Hill, ojiei-atcd a drag- line dredge on the Calaveras River 2 miles southwest of Jenny Lind during 1941 ; also on the Beers, Gertzen, and 0.sborn ranclies.

RPC. IV] MINES BY rOUNTIKS 253

Ltnicha Plana (iold Drc(l(/in(/ f'onipan!/ of Caiuaiiche, operated its (lre(l<,'e Xo. 2 on Mokelumne River in Calaveras County durinfr part of 1940. The dred-e has 84 buckets of G-cu. ft. capacity.

Loi-(J and Blshoj) (Lobicasa Co.), Box 812, Sacramento, operated three drajrline dredires on the Stockton Reservoir property on the Cala- veras River miles from Valley Sprin<rs in 1040. The drajline exca- vators used 3-, 1.]-, and l-cu. yd. buckets respectively. Operation of the 3-cu. yd. outfit was continued from July 1 to December 23, 1941. when the pround was worked out.

Mehrten Bros, operated a nonfloating washing: plant, to which gravel was delivered by carry-all in the Camanche district from January 1 to July 22, 1941. Prom 16,200 cubic yards of gravel, 146 ounces of gold and 15 ounces of silver were recovered.

Midas Placer Company, of Camanche washed 50,000 cubic yards of gravel in a dry-land plant between April 14, 1940, and the end of the year. Recovery amounted to 659 ounces of gold and 52 ounces of silver. During a few months of 1941, high-channel gravel at the Penn gold- copper-zinc lode property was worked.

Quartz Hdl Placers and 1. W. Ellis, Box 116, Angels Camp, oper- ated a stationary washing plant, to which gravel was delivered by a power-shovel, on the Quartz Hill property in 1941. Recovery from 11,270 cubic yards of gravel was 298 ounces of gold and 30 ounces of silver.

R. and M. Mining Company of La Porte operated a dragline dredge on Coyote Creek from January 1 to April 15, 1940; the excavator had a l]-cu. yd. bucket.

Ralford Mining Company, operated a dragline dredge with a |-cu. yd. bucket on the AVm. P. Iliatt ranch in the Campo Seeo district, from February 1 to July 10, 1941 . Recovery from 25,000 cubic yards of gravel was 199 ounces of gold and 14 ounces of silver.

San Andreas Gold Dredging Company, 960 Russ Building, San Francisco, operated two dragline dredges each equipped with a 1-eu.yd. bucket in 1940. Gravel was washed at the Airola-Costa, Albert Gut- tinger, John Guttinger, Batten, Bishop (Bowling Green), Calaveras Cement Company, Reed, Canepa, Byers, Fisher, Xuland, Nuner, Tanner, Bishop (Lot 29), and Solari properties. This company, Avhich was sold to Thurman and AVright, 960 Russ Building, San Francisco, on March 7, 1941, operated its two dredges on the Fisher, Ilageman-Huberty, Hageman, Lombardi, and Nuner properties in 1941.

Stagan Mining Company, 1440 North Hunter Street, Stockton, operated a dragline drdge on the Hunt and Robie ranches in the Jenny Lind district in 1940. At the Hunt ranch 86.000 cubic yards of gravel yielded 615 ounces of gold and 37 ounces of silver. At the Robie ranch, 414,000 cubic yards of gravel yielded 2287 ounces of gold and 145 ounces of silver. In addition, a dry-land dredge washed a small quantity of gravel on the Robie ranch.

Thompson, V,\ C, Box 77, Linden, operated a dragline dredge on the Calaveras River throughout 1940. In 1941 the dredge, equipped with 2-cu. ydr* bucket, Avas operated for 4 months on the Gregory, Sin- clair, and Dickhaut ranches li miles southwest of Jennv Lind. Later

254 I'LACKH MINMNC FOR (iOLD IX TAUFORNIA fBllll. 135

ill 1!)4], tlu' outfit was moved to Siskiyou County and operated by Shasta l)re(l,Miiji: Company.

ThuniKin and \Vn'(/Jif,' Huss Huildiii<r. San Francisco, ojierated dradine dredjre.s in Calaveras County in 1!)41. (See under Saii Andreas Cold I)red<rin<r Company.)

Tomboy Gold Mines, c/o \V. H. Wise, Kedondo lieadi, California, holds WO acres in sec. 19. T. 5 N., K. 12 E., M. D. Aecordinjr to J. J. McSorley, Mokelumne Hill, this property contains 8()()() feet of channel blocked out but not worked on the Happy Valley Blue Lead. The chan- nel is oi)ened by 3000 feet of drifting' from a 4()()-foot incline. The channel lias been crosscut each 200 feet and was found to be 250 to 350 feet wide. Gravel is .said to run rouj;hly to $3 per cubic yard.

Vallccito- Drift Mine. See pa<re 247.

VuncicI, C. F., Oakdale, operated a dra<?line dredge usinj? a 1 i-cu.yd. bucket at the Halter mine 5 miles west of Jenny Lind on Calaveras River from February 20 to April 26, 1941. From 87,848 cubic yards of gravel, 552 ounces of <rold and 27 ounces of silver were recovered.

What Cheer mine, of 140 acres in sec. 24, T. 5 X., K. 11 E., M.D., is owned by Mokelumne Placers, Ltd., Box 156, Plymouth, and contains a sejrment of the Chili Gulch Deep Blue Lead <,'ravel channel. Aecordinpr to J. J. McSorley, Mokelumne Hill, about 20 to 30 acres on the north and 20 acres on the .south have not been worked. The channel is the .same as that in the Deep Lead placer mine, which see. Mildred S. Barker, and three others, c/o Herbert E.. Barker, 641 Boulevard Way, Oakland, own a tract of 170 acres adjoining that contains this channel also.

WolJioIl Dredging Corporation of Natoma operated a dragline dredge on San Domingo Creek during part of 1940. The excavator had a 2-cu.yd. bucket.

Young cf- Son Co., Ltd., Mokelumne Hill, moved 40,000 cubic yards of gravel at the Yale and Allyn property to a stationary washing plant with tractors and carry-alls between April 9 and Augu.st 28, 1940; 420 ounces of gold and 37 ounces of silver were recovered.

'.See also Thurman, C. H., Co.sts in dragr'ine gold dredging: Am. Inst. MIn. Met. Kng. Tech Paper 1900, Mining Technology July 1945, 0 pages.

Sec. TV] MINES BY COUNTIES 255

El Dorado County

Below are notes on recent (1940-4;) placer mininfr operations in El Dorado County. Further details of mineral resources of this county are contained in State Mineralog:ist's Report XXXIV for 1938, includ- injr lists of gold mines both quartz and placer, by Lo<;an.

Barker Corporaiion, Box 696, Patterson, operated a dragline dredge on the Explorers property in 1942. The yield from 95,000 cubic yards of gravel was 754 ounces of gold and 94 ounces of silver.

Big Canyon Dredging Campany, Box 656, Fresno, operated a drag- line dredge with a 3-cu.yd. bucket during part of 1940. During 11 months of 1941, operations on Deer Creek yielded 3,160 ounces of gold and 321 ounces of silver from 540,000 cubic yards of gravel. During the first 7 months of 1942, operations yielded 1,269 ounces of gold and 137 ounces of silver from 250,000 cubic yards of gravel.

Duffy Property. George L. Duffy, Foresthill, holds placer mining claims in sec. 24, T. 13 N., R. 9 E., sec. 3, T. 13 N., R. 11 E., M. D., and adjoining sections, to cover a dredging project on Middle Fork American River. The river is a line between El Dorado County and Placer County, and additional details are contained in the chapter on Placer County.

El Dorado Dredging Corporation, Greenwood, operated a dragline dredge using a l|-cu.yd. bucket on GreeuAvood Creek and on Coloma Creek during 1940. In 1941, operations from January 1 to March 6 on Coloma Creek yielded 833 ounces of gold and 124 ounces of silver from 106,078 cubic yards of gravel. Equipment was moved to the Hughes property on Rock Canyon Creek, where 338,940 cubic yards of gravel yielded 2,630 ounces of gold and 281 ounces of silver. At the end of the year the equipment was on Irish Creek.

General Dredging Corporation, Natoma, operated a dragline dredge in 1940 and part of 1941 on the South Fork of American River near the point where James Marshall discovered gold in 1848. The dragline excavator had a l|-cu.yd. bucket. A second dredge with a 2-cu.yd. bucket was operated in this same area near Coloma in 1941. The smaller dredge was operated on a site near Shingle Springs during the last quarter of 1941.

Good Luck mine yielded 164 ounces of gold and 22 ounces of silver from 23,000 cubic yards of gravel in 1942.

Greenhorn Dredging Company, Youngs, operated a dragline dredge on the Middle Fork of Cosumnes River near Youngs during part of 1940 and 1941. The excavator had a 2-cu.yd. bucket.

Hook and Ladder mine at Smiths Flat, sec. 10, T. 10 N., R. 11 E., is held by Charles Fossetti, Smiths Flat. Lindgren has published a map showing the underground channels of this region and states that they are inter-rhyolitic but have yielded several million dollars by drifting. Bert Bryan of Smiths Flat worked a channel on this property known as the Gray Lead channel until 1932. An old shaft 114 feet deep was available at a point 350 feet gouth of the State highway. He sank an additional 38 feet, ran 330 feet south in bedrock, and raised to the chan- nel, which he worked for a length of 1,150 feet. He states that gravel

1 Logan, C. A., Mineral resources of El Dorado County : California Jour. Mines and Geology, vol. 34, 206-280, 363-365, map, 1938.

2 Lindgren, op. cit., U.S. Geol. Survey Prof. Paper 73. p. 173.

2.')() PLACF.R MINIXf; FOR GOLD IN CAMFOKNIA [Bull. 135

Avas 70 feet wide ami 1 to 3.\ foot deop at this point, and tliat 10 IVet back from tlic face a sample i-an $1 per enbie yard from a 2-foot depth of {jravel with jrold at $20.67 i)er ounce. He was workinjr down-stream (southward), and a drop of 11 feet in 50 feet of ehainiei made furtlier work too ditlKeult. He thinks that several hundred feet of this channel remain in place, but that it is cut off by the Deep Blue Lead channel. Workinjjs have been surveyed and mapped by Andrew Xesbit of Hanimon Enj;ineering Company.

Horseshoe Bar. W. I). lufram, (Jridley, operated a drajjline dred<ie on this bar on Middle Fork American Kiver just below Michipran Bluff durinj; part of lf)41. Dredpfinj-' was done in Placer County also, as the river passes throu<>h the property, and the center of the river is the county line.

Horseshoe Dredging Conipcniy, Youujrs, operated a drajxline dredge on the Frank Kipp property during part of 1940.

W. 1). Ingram, F'oresthill, operated dragline-dredging e(piipment on the following properties in 1941 : Craig Osborne, Craig Koyce, Craig Salt Water, Emma J. Hodgkin, and Red Raven. (See Hor.seshoe Bar al.so.)

Irish Creek Mining Company, Georgetown, operated a nonfloating washing plant on the Morgan property during part of 1940.

Lemroh Mining Company, 2401 Baysliore Boulevard, San Fran- cisco, operated a dragline dredge during part of 1940.

Max and Jnnetion mine yielded 110 ounces of gold aiul 15 ounces of silver from 14,000 cubic yards of gravel in 1942.

McQueen and Downing of Weaverville operated a dragline dredge on Carson Creek during part of 1940.

Orlomo Company, Box 548, Placcrville, operated a dry-land dredge, using a dragline excavator with l2-cu.yd. bucket, on Indian Creek throughout ]!)41.

Pafchen Property. Charles Patcheu, 80 Broadway, Placerville, holds 80 acres in sec." 18, T. 10 N., R. 9 E., M. D.. containing mile of stream gravel 100 to ."{OO feet wide aiul 8 feet deep in Martell Ravine. He states that this pays by hand-work.

River Pine Mining Company, 2432 l!)th Avenue, San Francisco, operated its drairline dredge on North Fork of Cosumnes River in sec. 26, T. 9 N., R. 10 E., M. D., near Xashville, during the last half of 1941. The dredge was operated in Amador County during the first half of the year.

Setter property yielded 548 ounces of gold aiuI 70 ouiu*es of silver from 77,500 cubic yards of gravel washed in 1942.

.Sturbuck Property. Frank I. Starbuck of Rescue holds 120 acres in sec. 10, T. 10 X.. R. 9 E., M. D., which was worked by placer miners in the early days. Two to 6 feet of gravel are covered by 0 feet of overburden. It is reworked from time to time in the rainy season and produ(!es a little gold. Part of the tract near the mouth of Sweetwater Creek was worked recently by a dragline dredge. Marcus Starbuck holds 40 acres in the adjoining section 17 that may pay by working with a dragline dredge. (}ravel is 250 feet wide and 10 to 15 feet deep. It was worked hand in the earl\- days. Bedrock is decomposed granite.

Sec. IVJ MINKS HV COUNTIKS 257

Tivo Clxiinul Mine. Tins is ;i consolidation ol' several old mines held bv W. S. Eaton, for whom E(\ (Jreen, IMaeerville, is aj'ent. More than 'ioOO acres in sees. H, 10, 15, 22, 27, ;U, T. 13 N., K. 11 E., M. D., 8 miles northeast of (Jeoretown are included. A channel containing' white (juartz boulders, and another containinj;' cemented pravel and andesitic bonlders are iVmnd here. Both have been worked by hydraulic and drift minin?-. The cemented "-ravel was crushed in stamp mills. Driftinji' has been done for a distance of 2500 feet south from Otter Creek, which cuts the channels. According to Bert Bryan of Smiths Flat, 2 miles of cliannel remain unworked in the vicinity of Kentucky Fiat, lie was plannin*;- to prospect the ground in the summer of 1944. Descriptions of old workings are contained in the references given below under the names of Kates, Kenna, Kentucky Flat, Mississippi, Tiedemann and Two Channel.

i:!ibl. : State Mineralogi.sfs Reports XII, pp. 114, 115, 117 ; XIII, p. 160 ; XV, p. 302 ; XXXIV, p. 2,'')1.

Van Dyke, Modrell, and Warner, Box 822, lone, operated a drag- line dredge with a -l-cu.yd. bucket on the Emma Gordon property dur- ing part of 1941.

Ventura mine of 90 acres in sec. 20, T. 10 N., R. 12 E., M. D., is owned by Ed ChrLstian, IMaeerville. A tunnel has been driven through a ridge containing a lava-capped channel ; 1300 feet of this on the Christian property connected with workings in adjoining property. Christian states that at least 80 acres of the property contains a gravel deposit but that little is known of the gold-content. The same channel mav exist in 100 acres held by F. H. Richardson of Placerville and in 160 acres in sec. 24, T. 10 N., R. 11 E., held by Mrs. Hedwig Bitzer and Alma L. Howard, Smiths Flat.

Widff Property. W. C. Wulif of Rescue holds 35 acres of placer ground, which produces gold by small-scale methods, in see. 8, T. 10 N., R. 9 E., M. D. The productive part is 30 to 36 inches deep. The gold has evidently come from eroded pockets in the immediate vicinit3\

Fresno County

Hopkins and Becker, 3231 Fernside boulevard, Alameda, operated a suction dredge invented by Becker on the San Joaquin River near Friant in 1941 and recovered 298 ounces of gold and 61 ounces of silver from 121,000 cubic yards of gravel. The dredge had a 6-inch centrifugal gravel pump, gasoline engine, and riffle tables mounted on a steel pontoon hull. The suction point could be lowered vertically 28 feet below water level.

Grant-Service Rock Company recovered 114 ounces of gold and 16 ounces of silver in preparing 339,955 tons of sand and gravel for con- crete aggregate in 1942. In 1943, recovery was 36 ounces of gold and 4 ounces of silver in preparing 210,000 tons of sand gravel.

Griffith Company and Bent Company, 418 South Pecan Street, Los Angeles, which supplied gravel for building the Friant dam in 1940, recovered 443 ounces of gold and 73 ounces of silver from 400,000 tons of gravel. In 1941, the recovery was 4,990 ounces of gold and 747 ounces of silver from 3,935,620 tons of sand and gravel. In 1942, recovery was 205 ounces of gold a-nd 29 ounces of silver from 121,700 cubic yards of sand and gravel.

258 PLACER MINING FOR GOLD IX CALIFORNIA [BuU. 135

Tinn Bar MiniiKj Corporation, lo'M Colley;e Avenue, Berkeley, operated a dredge on jirojierties of Grant Pacific Rock Company and V. Roulard in 1942.

Humboldt County

The eastern part of Humboldt County contains plaeer rravels on the Trinity and Klamath Kivers. A little prold is produced by small-scale methods from beach sand. A number of these operations and properties have been described in a recent rejjort of the State Mineralo<i:ist. The princii)al i)roducer in recent years has been the Peai-ch miiu* described below.

Orick Placers, Inc., operated a washing plant in the CJold lilutf dis- trict in 1943 to recover gold from beach sand.

Pcarch mine of 180 acres in sec. 32, T. 11 X., K. 6 E., II.. formerly owned by P. L. Young, (Orleans, has been sold to Roy McCJain, ()rleaiis, who is operating it (1940). The proi)erty is 1 mile northeast of Orleans on the dirt highway to Happy Camp. An old terrace of Klamatii River with bedrock about 50 feet higher tlian the present river contains a placer deposit 80 feet thick at the face of the present hydraulic pit. Only the lower part of the deposit is gravel with boulders of a maxinuim diameter of 18 inches. Overlying this is a great thickness of fine over- burden and soil. The slate and chloritic schi.st bedrock dips steeply in several directions.

During the water-sea.son the mine is kept in operation for 24 hours per day by a crew of 10 men. A mile and one-half of Hume from Pearch and Cheney Creeks has a capacity of 1,300 miner's inches with a head of 225 feet at the mine. Three giants are set up, one with G-inch nozzle- opening, the other two with 5-inch openings. They are supplied with water by means of 840 feet of 36-incli and 30-incli pipe, 900 feet of 20- inch pipe, and 2,800 feet of 15-inch pipe. Gold is recovered by means of wood-block riffles in a 'Y' sluice reaching both ends of the pit and di.s- charging to Klamath River. To reach the river from one end of the pit, 192 boxes, each 12 feet long, are required. The 'Y' branch to reach the other end of the pit contains f)4 boxes. (Jrade is half an inch per foot. .McCJain estimates that he miiu's 1,000 cubic yards per day during a working-season of 5 to (i months. Water wheels furnish power for compressed air aiul electric lights.

Production for 1939 is given by the U. S. Bureau of jNIines - as follows: "Cleaning bedrock at the Pearch hydraulic mine on the Kla- math River northeast of Orleans yielded 154 ounces of gold and 23 ounces of silver." Figures on production for 1940 are not available, but in 1941 the mine produced 266 ounces of gold and 38 ounces of silver from 128,500 cubic yards of gravel.

Bibl. : State Mineralogisfs Keport.s XI\-, p. 4114 ; XXI, p. :n5.

' Averill, C. V., Mineral re.sources of Humboldt County : California- Jour. Mines and Geology, vol. 37, pp. 4y!-r>28, iy41.

"Merrill, C. W., and (Jaylord, H. M., Cold, .silver, copper, lead, and zinc in Cali- fornia: U. S. Bur. Mines, Minerals Yearboolt lOSfl, p. 2:{3, 1940.

MINKS UY rorxTiF.s

3. S2. rearc-h mine, Huiiil)<>l(lt County. Photo hy coin-tesi/ of Hoy MiGai 'tnleil jroni Caliloriiiii Jonnidl of Minrs <inil (IroU.ffti, October l'>'il, p. 513.

Imperial County

The placer pold produetiou of Imperial County has been small in recent years. The followinj; notes are extracts from a recent report by Sampson and Tucker/ contained in the California Journal of Mines and Geolojj-y for Awil 1942. The same issue contains a few notes on gold placers by Ilenshaw.-

Gold Delia placer mines are in sec. 20, T. 13 S., R. 19 E., S.B., 9 miles east of Glamis, and are owned by Cold Deltas Corporation, C. R. Zappone, president, 1001 Subway Terminal Building, Los Angeles.

Placer gravels in washes of present water courses from the Chocolate Mountains have been developed by a shaft sunk 300 feet through uncon- solidated gravel to bedrock. Cuts and shafts indicate a body of gravel 2 miles long and half a mile wide. A 6-f()ot thickness of gravel at the bott(mi of the 300-foot shaft is said to contain $0.50 to $2.00 per cubic yard in gold.

Picacho Basin mine (Placer). The basin consists of low, rolling hills covered in part by washed gravel and detritus from the neighboring hills. These superficial deposits are gold-bearing and have been washed by Mexicans for years and recently, by dry Avashing machines. The gravels have been worked along the arroyo between the Picacho lode mine and the old village at Picacho. It is reported that the gold-bearing gravels have an average value of 35 cents per cubic yard. These gravel deposits are 25 miles north of Yuma. Idle.

IMbl. : State Mineralogi.sfs Report XXII, p. 200 ; Hull. 92, p. 15G.

1 Samp.son, R. J., and Tucker, W. 15., Mineral re.'iource.' of Imperial County : Cali- fornia .Jour. Mines and Geolojjy, vol. "S, pp. 10.';-145, l'J42.

-Henshaw, Paul C, C.eology and mineral deposits of the Cargo Muchacho Moun- tains, Imperial County, California: California Jour. Mines and Geology, vol. 38, p. 190,

260 i'LA(i;k minin(; kok com) ix cArJFOKNiA [Bull. l:>.">

Potholes (IMacor). These dry phan-rs ;iie lociitcil 10 miles iiortiieast of Yuma, Arizona, and several miles west of liafruna Dam; elevation 150 feet. Tlie {jold-bearin}; <;ravels of this i-e<iion were extensively worked in the early days by Indians and Mexicans and are now worked out. Value of the {jold produced from the Potholes placers is reported to have been $2,000,000.

. : State MineraloRisfs Hepnrls XIF, p. 242; Mil, p. :! H ; XXII, p. 2t;i ; IJnll. 92. p. LIS.

Kern County

Holcoinh Valley Placer Company, lessee of the Monarch Rand mine in the Randsburg,;: district, prodiiced in 104.' a.s a byproduct of a ])lacer operation carried on primarily for scheelite. (Iravel was delivered by a carry-all to a stationary washing plant.

Monarch Rand Mininfj Com])any opei-ated a dry-land drede in the Randsburp: district intermittently during (5 months of ]942 for the recovery of sciieelite and gold.

Placer Concentrators produced gold in 1948 as a byproduct from a placer sdieelite operation on the Patsy and Victory Xo. 2 mines in the Randsburg district.

Hand Cold Dredging Associates, Russ Building, San Francisco, installed a connected-bucket-type dredge with eighty-two 3-cu.ft. buckets to work the Tungold mine 1] miles noi-thwest of ]andsburg in 1942. Tlie dredge was moved from Shasta County, wliere it liad been ojierated by Roaring River Dredging Company. It was reconstructed, and jigs were added in order to recover .scheelite as well as gold. ()i)erations started on November 1, 1942, and continued until June 10, 1948. when the dredge capsized. It wa.s righted later in the year as described by Macaulay.

Los Angeles County

Ciold was discovered in Los Angeles County in 1884, and the placers of San Franci.squito, Placerita, Casteca, and Santa F'elicia canyons were worked between the years 1884 and 1888 by the ])riests of San Fer- nando and San Buenaventura Missions. The placers of San (iabriel Canyon were worked by the i)riests of San (Jabriel Mission and also by the native Californians until the discovery of gold in northern Cali- fornia by Mai-sliall in 1848 at Sutter's mill.- In i-ecent years jiroduction of jilacer gold in this count\' has been small. Two pi'oducers of sand and gravel for the construction indu.stry reported the recovery of small amount.s of placer gold from llie San (iabiiel district in 1948.

' Mac-aulii.v, W. I!., HiKlitinj; cap.'i/.i-tl dridR.- takes .">0 miiiute.s: Rng. and Min. Jour., April l!t44.

- Tinker. W. H., ami .'-aiiipsun, R. .1.. iUiieral re.snurces of Ios Angeles Coiint.v : ('allfornia .lour. .Miiie.s and Ceolony, vol. ;i;{. pp. 17:1-270. l!t:!7.

Hrartle.v, W. W.. California mineral pro.lnetion. 1!t24: ("alifornia Min. lur.. Hull. !ir.. p. 47. I!t2...

See. IV] MINES 15Y COUNTIES 2(51

Madera County

H. A. Berg, Box 581, Madera, operated a .suction dredfe on the P're.sno River in the Dennis district in 1041, and recovered 257 ounces of gold and 74 ounces of silver from 22,000 cubic yards of prravel.

Cassanrang Ranch. Two suction were operated on this ranch in the Dennis district wheiv the Fresno Kiver passes through it, in 1941. Operators were E. J. (Jibbons and Richard A. Cassauran<,'. Madera.

G. E. Nohlc d' Sons operated a suction di-ed<i:e on the .1. T. Pierce ranch in the Potter Kidge district during nearly all of 1942. Recovery from 7790 cubic yards of gravel was 118 ounces of gold and 35 ounces of silver.

Polk Ranch. Suction-dredge operations on this ranch in the Potter Ridge district produced 148 ounces of gold and 82 ounces of silver from 9000 cubic yards of gravel in 1942.

Mariposa County

Although small placers yielded many millit)ns of dollars to early miners in Mariposa County, the rich Tertiary channels found in counties farther north are lacking because the protective blanket of lavas and other volcanic ejecta did not extend this far south. Hence the placers of Mariposa are now less important than those of other counties along the Mother Lode. Short descriptions of the many lode-gold mines of this county are contained in State Mineralogist's Reports XXIV and

Barker Corporation, Hornitos, operated a dragline dredge on Eldo- rado Creek 1 mile from Hornitos in 1940. In 1941, operations were continued here and on the following other pro])erties: Givens, Trabncco, Turner, and Waltz in the Hunter Valley district, and the Adams, Explorers, Inc., Munn, Penrose, R. AVilliams and Stratton in the Mother Lode district. In 1942 there were 22,000 cubic yards of gravel washed at the Kehoe property, Avhich yielded 112 ounces of gold and 32 ounces of silver; 109,000 cubic yards Avashed at the J. Lord i>roperty yielded 833 ounces pf gold and 229 ounces of silver ; and 16-3,500 cubic yards washed at the Trabncco property yielded 1016 ounces of gold and 280 ounces of silver.

Thurman and Wright, 960 Russ Building, San Francisco, operated a dragline dredge with 4J- and 6-cu.yd. buckets on property of the Crocker-Huffman Land and AVater Co. during the last half of 1941. Operations Avere continued on Burns Creek during part of 1942.

1 Julihn, C. E., and Horton, F. M., Mineral indu.stries of the United States: Cali- fornia, Mines of the southern Mother Lode region Part II, Tuolumne and Mariposa Counties: U.S. Bur. Mines Bull. 424, pp. 1-179, I'.MO.

- Laizure, C. McK., current mining activities in the San Francisco district with special reference to gold: California .Jour. Mines and Oeolfigy, vol. 31, pp. 27-4*!, l!)3ri.

Laizure, C. McK., Mariposa County: California l)i\-. Mines, Mining in California, State Mineralogist's Rept. 24, pp. 79-122, 1'J2S.

262 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Trchor Corporation, Box 51, Mariposa, with Robert D. Mueller in charge, operated a draprline dredg:e with 2-cu.ft. bucket on the Chase Ranch in the Hunter Valley district in 1940. Earlier operations were conducted at Mormon Bar and A*rua Fria Creek. In W41, operations were conducted on the followin}; properties: Fretz, Gaskill, Machado, Trabucco, Turner, and Waltz. In 1942, operations for 8J months on the C. C. Pierce property pn Corbett Creek yielded 289 ounces of and 57 ounces of silver from 100,000 cubic yards of }?ravel.

MERCED COUNtY

P. H. Bottoms, Box 121, Merced Falls, operated a drajline dredge with 2-cu. yd. bucket in the Snellinj; district during? part of 1940.

Merced Dredging Company, 1805 Mills Tower, San Francisco, operated an electric connected-bucket dredn:e with sixty 10-cu.ft. buckets half a mile south of Snellinfr in 1940, 1941, and part of 1942.

Sayi Joaquin Mining Company, 1805 Mills Tower, San Francisco, operated a connected-bucket dred<rc with sixty-four 10-cu.ft. buckets 3 miles west of Snelling in 1940, 1941, and part'of 1942.

Snclling Gold Dredging Company of Snellinjr operated two electric connected-bucket dredges on the Merced River between Merced Falls and Snelling: throughout 1940 and 1941, and during part of 1942. The property is in sees. 10, 11, 12, T. 5 S., R. 14 E., M. D., and covers a deposit of uiicemental gravel and sand 10 to 20 feet deep with bedrock of volcanic asli. One of the dredges has seventy-two and the other sixty-six 7-cu.ft. buckets. Otherwise the dredges are much alike with steel hulls 42 by 96 feet and the usual riffle system.

Thurman and Wright, 960 Russ Building, San Francisco, operated a dragline dredge with a 6-cu.yd bucket on land of Crocker-Huffman Land and Water Company, in 1941. This operation was partly in Mari- posa County and partly in Merced County.

Yuha Consolidated Gold Fields, 351 California Street. San Fran- cisco, operated a connected-bucket dredge with seventy-two 9-cu.ft. buckets 4 miles cast of Snelling in 1940 aiul part of 1941, in T. 5 S., R. 15 E., M. 1). The dredge and part of the property were taken over from La (I range Gold Dredging Company in 19.{0. Gravel ranged in depth from 18 to 36 feet, and bedrock is slate near Merced Falls but is volcanic ash on the lower part of the tract. A little platinum was recov- ered with the gold.

Sec. IV] MINES BY COUNTIES 263

Nevada County

Some of the larpjest known reserves of placer gravels in California are in Nevada County. Long stretches of Tertiary river channels that were formerly the sites of great hydraulic mines remain nnworked as a result of the injunction-decision of Judge L. B. Sawyer in 1884 against North Bloomfield Mining Company restraining that company from dis- charging debris into the streams. Federal legislation passed in 1893, called the Caminetti Act, created the California Debris Commission. This act is printed in full in the appendix of this report. For large hydraulic mines on the Sacramento-San Joaquin drainage, tailing must be restrained by dams. The Upper Narrows dam on the Yuba River was built for this purpose and was completed in 1939, but only a little hydraulic mining has been done above it to date (1945). One reason for this was Limitation Order L-208 of the War Production Board, which shut down nearlv all the gold mines, remaining in effect from October 8, 1942 to July i, 1945.

Estimates of yardages available for hydraulic mining above this and other dams have been made by Jarman and Bradley.- A few recent operations have been described in a report by Logan and older ones in a report by MacBoyle, but MacBoyle's report is out of print.

Calaveras Gold Dredging Company operated a dragline dredge at Steep Hollow in the You Bet district from April 8 to August 20, 1940.

Clerkin pi'operty consists of 156 acres of patented land in sec. 24, T. 17 N., R. 7 E., M.D., near French Corral, owned by W. P. Clerkin of French Corral. Clerkin states the ground contains 30 to 40 acres of gold-bearing gravel, of which a 60- to 70-foot depth contains practically no gold. From 8 feet to 10 feet at the bottom is blue gravel, and the last foot contains most of the gold. Clerkin thinks that this deposit repre- sents a high bench of the old Eocene channel about 100 feet wide and adjoins the bedrock tunnel claim of the French Corral placer. Clerkin works the property for about 2 months in the spring of each year with 750 miner's inches of water that flows from Bloody Run Creek from melting snow.

Dakin Company, 917 Sacramento Street, San Francisco, operated a dragline dredge at Champion Flat along Deer Creek from January 1 to March 1, 1940. The excavator was equipped with a li-cu.yd. bucket.

Esperance. See French Corral.

French Corral placer is a property of 1,700 acres in sees. 23, 24, 25, 35, T. 17 N., R. 7 E., M. D., including the Kate Hayes, Esperance, Fra.ser and Alexander, Bedrock Tunnel, and Milton placer mines, owned by G. M. Standifer, Balfour Building, San Francisco. The property contains approximately 1 mile of unworked length of the Eocene channel worked by hydraulic methods at North Bloomfield, North Columbia, Badger Hill, American Hill, North San Juan, Sweetland, Birchville, and French Corral.

1 Jarman, Arthur, An investigation of "the feasibility of any plan or plans whereby hydraulic mining operations can be resumed in this state" : California Min. Bur., Mining in California, State Mineralogists Rept. 23, pp. 54-116, 1927.

- Bradley, W. "SV., Dams for hydraulic mining: California Jour. Mines and Geology, vol. 31, pp. 345-367, 1935.

3 Logan, C. A., Mineral resources of Nevada County, gold placer mining: Cali- fornia Jour. Mines and Geology, vol. 37, pp. 431-436, 1941.

♦ MacBoyle, Errol, Mines and mineral resources of Nevada County: California Min. Bur., State Mineralogist's Rept. 16, pp. 91-108, 1919.

264 I'LAIKK MINING KOK (H)IA) IN CALIFOHNIA [Bull. 135

In November, 1040 a report was made on this property by L. A. Smith, uho sank some shafts to sample the frravel and who had the results of some drillinjr that had been done about 1938. The foUowinj; is abstracted from Smith's report : About one-third of a mile of channel on this property has been |>artly worked by the hydraulic method, and the resulting; excavation is as the Esperance pit. An averajre of about 65 feet of the top jiravcl has been i)iped off of an area rou<rlil>- 600 by 1.500 feet. The bottom jrravcl remaininji- on bedrock measures rou<rhly 200 yards wide by 500 yards loni' by 12 yards dee]). Gold content of this 1.200,000 cubic yards should be hiohcr than the channel averagre, and the deposit can be worked mechanically. Smith's sampling results in this bedrock gravel area turned out as follows:

Shaft No. 1 121.4 ft. OO.Tc' p.'i- cii.vd. B<Mlr..cU Shaft Xo. 2 :U.r. ft. 41.0c per cu.yd. Bt'drock Shaft No. 4 24.5 ft. 3G.0<* per cu.yd. Bedrock

Average of the aiiove bedrock shafts — 45.1 Shaft No. 3 S.O ft. 23.C<' per cu.yd. Xo bedrock

Avera>;e of the above four shafts — 13. Ic' Cut No. 1 30.0 ft. 3G.0( per cu.yd. No bedrock

(Extends above collar of shaft No. 1)

Cut No. 2 5.0 ft. 45.0'' per cu.yd. No bedrock

(E.xtends above collar of shaft No. 3)

Average value of all cuts and shafts — 41.4(f per cu.yd.

The gravel that was sampled was tough and tuicemented in general, but it contained lenses of cemented gravel. It was washed through a trommel 4 feet long and 14 feet of sluice box. Smith estimates that 70 to 90 percent of the gold was recovered. lie thought that a moderate amount of scrubbing in a large trommel would insure a good recovery of the gold.

The un.stripped ground north of the p]sperance pit was drilled about 1938 with the results given below. This work was done as explora- tory work and all holes are therefore not in the channel. The lines were roughly 1,200 feet apart, and the number "2" was not used.

Line No. 1 has three holes in the channel — holes No. 7, No. 9, and No. 10. The average depth is 89 feet and average value 21.1 cents per cubic yard. The width of channel is about 600 feet.

Line No. 3 has four holes in the channel — holes No. 6, No. 7, No. 8 and No. 9. Using holes No. 7, No. 8 and No. 9, Smith figured a 500-foot width with average depth of 56 feet and average value of 14 cents per cubic yard.

Line No. 4 is made up of three very poor holes, the deepest of which (128 feet) did not reach bedrock. The channel at Line 4 is evidently comparatively narrow for an unknown distance or until it widens again in the Birchville pit.

The Line 1 drill holes appear to confirm the shaft samples in the shallow ground. Smith as.sumed 30 feet of 40-cent bottom gravel at Line 1, and 59 feet of 12-cent top gravel overlying it and thus arrived at the 89 feet of 2 1.1 -cent gravel shown by the drill holes.

Line 3 drill holes do not stand up to the average indicated by Smith's shaft results. Thirty feet of 40-cent bottom gravel at Line 3 would show a 21 -cent average for the 56-foot average depth without assuming any values in the top 26 feet.

Sec. IV] MINES BY COUNTIES 265

Before these drill hole results are accepted, Smith believed they should be checked by sinking two or more shafts over selected, drill holes. He did not sample the upper or overburden gravels, but pan tests that he made would indicate a value in the neighborhood of the recoveries reported by Schroder and others who hydraulicked top gravel from the Esperanee pit. These reported recoveries run from 10 to 17 cents, old price, or an average of probably 20 cents per cubic yard at present price of gold. This figure is confirmed to some extent by one sample taken near his shaft No. 1. This sample began at approximately 30 feet above bedrock and extended to approximately 60 feet above bedrock, with an average gold content of 36 cents per cubic yard for the 30-foot sample.

Smith proposed to work by mechanical methods the gravel already stripped in the Esperanee pit, about 1,200,000 cubic yards, then to pros- pect the unstripped ground and strip by the most feasible means, either mechanical methods or hydraulicking. He expected this work to expose an additional 2,400,000 cubic yards of gravel of a grade that would show a profit if worked by mechanical methods. In the fall of 1945, such a project had not yet been started.

Water for this property is obtained from Shady Creek, and is brought into the Pine Grove reservoir by means of a 4-mile ditch. The original capacity of the reservoir was 300 acre-feet. Applications have been made for 53 second-feet or 2,120 miner's inches of water.

GrcenJioni Dredging Company operated a dragline dredge at Quaker Hill in the You Bet district from January 1 to December 31, 1940, using an excavator equipped with a 2-cu.yd. bucket.

Hall and French. See French Corral.

A. B. Innis of Nevada City operated a dragline dredge equipped with a 14-cu.yd. bucket at the Malakoff mine from October 16 to Decem- ber 31, 1941. The yield from 72,000 cubic yards of gravel was 333 oun'ces of gold and 33 ounces of silver. The operation was continued in 1942 and the yield from 146,000 cubic jards of gravel was 694 ounces of gold and 64 ounces of silver.

Kate Hayes. See French Corral.

Kanfield and McKhiley of Lincoln, operated a non-floating washing plant on the Parker Ranch from June 27 until September 13, 1940. Kaufield and Danison of Nevada City operated a dragline dredge on Columbia Hill near North Bloomfield from March 1 to April 20, 1941.

M. K. Gibson Mining Company, Grass Valley, operated a dragline dredge on the Elder, Martel, Neirzert, and Thomas properties in 1941.

Milton. See French Corral.

Omega mine is in Sec. 16, 17, T. 17 N., R. 11 E., M. D., 3 miles southeast of the town of Washington. It is owned by South Yuba Mining and Development Company, Charles A. Kaas, secretary-manager, 420 Market Street, San Francisco. The last mining was done in the season 1941-42, ending in the summer of 1942, by Omega Company, of which Jack Little was manager.

A new 30-inch pipe line has been installed to take water directly from the ditch, giving a pressure of 175 pounds per square inch. The old pipe line from reservoirs is also a 30-inch line, but it gives only 90 pounds per square inch pressure. Three resei'voirs hold about 35 acre-feet of Avater. The company takes 5000 miner 's inches of water

2(jt) i'LA(i:r{ MIXING von cold ix California [13u1I. lo

Iroiu tlu' Si)utli Fork (f the Yuba Ivivei- under old water-rijrlits. Tliis amount is usually available to about the niidtlle of July, then the amount Tadually deelines. The nuiin ditch system is 12 miles ionr and starts just below Lake Spauldiujr. ()u'-third of this 12 miles is flume 4 feet by () feet, ineludinji- 4 miles at the stai-t. The flume was i-epaired with 1200 M board feet of lumbei- in 1!>41. A lower ditch system, i)art of which is 'i- by 4-foot fhime, picks uj) water from various canyons to feed the reservoii's with 1200 minei-'s inches of water. It is 7 miles lon'. Other e(|ui]>ment includes a camp to house 7") men, and a sawmill with a capacity of l(i M to 20 board i'cot of lumber pei- day operated by steam ])()wcr. It includes two (iO-inch saws, a foui--saw edjier, and a cutolf saw. Lumber is ])roduce{l only for the use of the mininjr company.

(!()ld is recovered in a sluice 3 feet wide, ',i\ feet deep, aiul mile loup', erpiipped Avith cross rifHes of .'{0-pound and 4r)-p()und steel rails. 'IMie jrrade is 6 inches in KJ feet. Duty of the water is about cubic yards jier miner's inch ])er day. ledrock is a slaty schist.

Accordiujr to Theodore TarscMi of Nevada City, who was super- intendent of the last operations, the coni])any holds about .'{000 acres of land containin-;' 2:),0()0.000 to ;U).()()(),000 cubic yards of jrravel. The face of the pit is carried (iOO feet wide and loO to 18.") feet hih in an Eocene chaniuM I.IOO feet wide.

The ()me<:a ('()mi)any bepan hydraulickin<i' .March 0. 1!41. utili/.iufr storajie space for tailiniz' in the recently completed I'pper Narrows Debris Dam at Smai-tsville. Duriuti' the season the comjiany washed 42f>.()."{7 cubic yards of jzravel, which yielded l."{02 ounces of >()ld and 4f) ounces of silver. In ]f)42 the mine was operated by Omejra Com- l)any, and lessees from January 17 to July 7. The yield from 818,17.') cubic yards of jrravel was 1740 oiuices of <rold and r)4 ounces of silver. Tn 1043 bedi-ock was cleaned, yieldin<r (54 ounces of jiold and 2 ounces of silver.

Pilot DicdijiiKj Comixiiifj, {'ottouwo(Hl, operated intermitteutl\' in 1!)40 on the C'olebui-n ))roi)ei-t\- with a drajiline dredge.

Ihlief urn Mine. See Western (lold, Iiie.

William Hichtcr tO Sons oj)erated a dra-iline dredj-e at Sct)tts Flat from .January 1 to October 13, 1!)4(). Tn i;)41 this firm operated a dra<4- line tlredjie on the Donnell' and Johnson property.

Sun J nan (iold Company, F. Ti. ]\Iorris, president, ]\Ionadnock Buildini", San Francisco, liolds 5484 acres of ])atented mininjr claims on San Juan Kid;:e principallv in the followiu<r sections: Sec. 3(). T. 18 N., 1?. 8 E.; Sec. 1, T. 17 N.. K. 8 E. ; Sees. 1, 2. 4, .'). (i, 7, 8. !), 11, 12. T. 17 N., K. fi E.; Sees. 3.1, 3(j, T. 18 N., K. E. ; Sees. 1(1. 21. 22. 31. T. 18 N., It. lOE., M. D.

These holdinjis include the famous MalakolT hydraulic mine form- erly operated by North Bloomfield .Mining Company. Accoi-din<r to officials of the i)resent company, this old i-ompauy recovered .$2,830,000 during' the period from 1870 to Februaiy 1884 from n-avel that yielded 12 and a fraction cents ])er cubic yard with rold at $20. ()7 ounce.

In tlie vieinity of North Columbia is a i)art of the same channel that has been stripped by old hydiaidic mininjr to a dejith of abont 150 feet. Gravel still remains in this i)art of the channel to a deptli of about 300 feet. ]\raps in the ])o.ssession of F. L. Morris sliow that this has been drilled to determine the yold content for a distance of 2), miles,

Sec. IV] MINES BY COUNTIES 267

Fig. S3. Badser Hill property of San Juan Gold Company.

on the Central, Consolidated, and Western placer mines. Rows of holes about 500 feet apart -were drilled across the channel, and the distance between the holes is about 200 feet. Morris states that this sampling has indicated a gold content considerably higher than the recovery men- tioned above for 100,0000,000 cubic yards in a strip down the center of the channel 600 feet in width. As bectrock was reached in only small areas of the old workings, gravel remaining in this stripped part of the channel should be better than the average gravel already mined because of the concentration of gold on bedrock.

Application for new water-rights has been made as follows : Hum- bug Creek, 20 cubic feet per second; Spring Creek, 15 cubic feet per second ; Grizzly Canyon, 25 cubic feet per second ; Bloody Run, 50 cubic feet per second ; Middle Fork of Yuba, 300 cubic feet per second. Rights are held on Wolf Creek for 25 cubic feet per second and on Malakoff pit for 5 cubic feet per second. Old ditches are being retained and may be reconditioned to handle all water except that of the Middle Fork of Yuba River. Estimates have been made on the cost of a new system for this water of $800,000 for flume and dam only or $1,540,000 total for the entire system complete to the mine. This includes 22 miles of flume and 2 miles of ditch.

As the cost of installing this water-system is high, owners of the property are considering the installation of mechanical methods of mining instead of hydraulicking. If mechanical mining is used, storage of tailing on the property may prove feasible.

A. B. Innis operated a dragline dredge with a 1 |-cu.yd. bucket at the Malakoff mine from October 16 to December 31, "1941. The yield from 72,000 cubic yards of gravel was 333 ounces of gold and 33 ounces of silver. In 1942, the yield from 146,000 cubic yards was 694 ounces of gold and 64 ounces of silver.

Western Gold Incorporated operated the Relief Hill mine by the hydraulic method in 1941 and was one of the first companies to utilize debris storage behind the Upper Narrows Dam on the Yuba River. W. H. Taylor, 942 Russ Building, San Francisco, is president ; and Claude E. Clark, Graniteville Star Route, Nevada City, is manager. The mine is 3 miles east of North Bloomfield in sees. 4, 9, T. 17 N., R. 10 E., M. D.

1'I;A(1:K MININd VOH (i(>I,l) IN CAIJIOUNIA |r.. 1

I-'ic. SI. W.-st.-i-n I ;.

J'liul,, l,ji lli. F. I.\mh

Janiiair"' estimated that (i.OOO.OOO eubie of .travel have already been washed at this mine and that r),()U(),()()() to l.l.OOOjHH) eid)ie yard's were still available, lie stated that owners estimated that enbic yards were available at that time. Present ownei-s estimate a still liijrher yardajie available. Drift mining; lias been dcnie at this property as well as hydraulic niininj>'. Dnrintr the war the mine has not been in operation because of shortare of labor and Limitation Order L-208 of the "War Production ]5oard. The operators are planninjr to open up the mine for hydi-aulickinji on a lare scale when labor and materials are available.

The following deso-iption of an carlici- ])criod of o])ei-ation at thi.s min is fi-om Gardner and Johnson:''' The Relief Hill Mininji- Company bejran operations near ('am|)tonville in the antunui of lU'M and worked 4 months in lfi;32 before tlie water supply failed. An old mine was bein<r rejuvenated; the }rravel was 200 feet thick. About .lOO miner's inches of water was used during: the season. A total of ]0()() inches will be used when the mine is fully reopened. The old pit Avas cleaned and virrin {jravel reached in 1!):2 just as the water played out. Tailinrs were imjiounded behind dams in a dry canyon. The ditch line is 7 miles lon<r. The pipe line is 14 to 22 inclies in diameter, and the effective head is 210 feet. The sluice boxes are 48 inches wide; riffles are wooden blocks. A duty of cubic yards ))er 24 hours ]>er miner's inch is expected. A crew of 15 men worked 120 days in 1932.

Wifdndnttc Dndcjincj Compaiwj, Box 228, Nevada City, operated a dragline dredge, using a 2J-cu.yd. bucket on the Perrin and Pingree Ranches from October 18 until December 31, 1940. The yield from

Jarman, Arthur, op. cit.. p. 11 1. "Gardner, K. 1., and Johnson. ('. M., Pari II, Hydraulic-kinR, oti-. : l.'.S. IJnr. Miii.

inhiR in the we.stern T'nited .Sii t;TS7. p. ,52, 11134.

Sec. IV] MINES HV COUXTIKS 260

H7,()()() cubic yanl.s (A yravel was 771 ( of jiold and lOf) ounces of silver. The company also operated a draj-line dredge on property of the Alpha Stores in" the You Bet district durinr 1940. In 1941 this company did further work on the Perrin and Pinfzree properties. The yield from 1 :?().()()() cubic yards of firavel washed at the Perrin property was 118() ounces of <rold and 155 ounces of silver; the yield from 70,000 cubic yards washed at the Pinp:ree property was :VA9 ounces of jrold and 58 ounces of silver.

You Bet )iii)U's include many of the old hydraulic mines famous in the early days of that method of minino-, such as the followinor : Palmyra, Newark, Arkansas and Greenhorn, Starr, Red Dofr, Missouri Canyon, Gail Placer. Rose and Duryea, Emigrant, Smith and Powell, Chicken Point, Atkins and Taylor, You Bet, Brown Bros., Washington, Browns Kill, Niece and "West, Birds Eye Canyon, Poverty, and Walloupa. The group includes 1150 acres of patented land and 120 acres of locations in sees. 25, 35, .36, T. 16 N., R. 9 E. ; sees. 29, 80, 31, 32, T. 16 N., R. 10 E. ; sees. 2, 11. 14. 15, T. 15 N., R. 9 E. ; sec. 6. T. 15 N.. R. 10 E.. M. D. ; also 151 acres of timberland in sec. 28, T. 16 N., R. 10 E. ; also the following ditches: a 12-mile English ditch Avith the fir.st right on 1500 miner's inches from Steep Hollow Creek; a 5-mile Star ditch on the south fork of Greenhorn Creek with the second right to 500 miner's inches of water, and 13/21 interest in the Irish ditch with the second water right on Steep Hollow Creek. This property is now owned by Alpha Stores, Ltd., Fred F. Cassidy, president, Nevada City, California.

Immense yardages of gravel were washed at these properties by the hydraulic metliod in the early days from one of the great Tertiary river channels, but large yardages still remain unworked. The Jarman'' report of 1927 quotes p. A. Goodale as estimating that the property still contains 12,000,000 to 24,000.000 cubic yards of gravel containing enough gold to pay for hydraulic mining. Tom Brady, who lives at You Bet and who holds the adjoining Jupiter group of 100 acres in sec. 31. T. 16 N.. R. 10 E., states that a part of the channel starting at a point east of You Bet and running northward has never been worked, except a little on the surface. Brady says that the best content of gold is found where the bedrock starts to rise on the west side of the channel and that this has not yet been mined in this particular section of the channel.

The following quotation is from the Colfax folio by Waldemar Lindgren

"At Red Dot; .nml Iliiwkins Ciinyttii, Yon Bet, the deep frravel has aRain l)een exi)(>sed and is heyoiid doubt ooiitimious between the two points. The gravel here is similar to that at QuaUer Hill. The deepest jyavel has been hydraulicked only in the jilaces mentioned bnt considerable drifting by means of tunnels and inclines has l>een done from Niece and West's claims for H miles northeast on the Steep Hollow side. The channel has very little fall, the average elevation being 2620 feet. It is estimatetl 47,000,000 yards have l)een removed, leaving over 100,000,000 yards available. Much of this would be ditHcult to wash on account of lack of grade. Ueports of yield and grade of gravel are not available but the You Bet diggings have probably produced .$.3,000,000."

' Jarman, Arthur, op. cit., pp. 44-116.

l.,indsren, Waldemar, U.S. Geol. Survey Oeol. Atlas, Colfax folio (no. G6), p. 9,

270 IT.ACI'.U MININ'C FOR COI,!) IN ( AMIOUMA [ Illll I. 1 o")

V(ii Milling ('(iu|);iii\- did sonic liydriiiilic iiiiiiiiir on lliis prop- erty in the winter of l!i;M4' jilter bniltlin- ;i dclnis diun ;ind jrcttinr a permit tVoni tlic ('alirofiiiji Debris Comniission. \Voi-k Wiis stopped ill l!n4 by a court injunction on tbe ground that the water below the dam was rendered unfit for (h)mestic |)urposes on account f)f its turbidity. In im.") many of the claims were leased to (Miincsc niineis, who did some drift niiniu;r that is rejjorted to have been xcry product i\t'. Apparently the last hydraulic mining' was done under the supervision of .). \V. Scott about IICM. He used miner's inches of water under a 2S()-foot head and recovered in a sluice tiia-t had a slope of 7 inches to 12 feet. Hydraulic minin: was done on the Ked Doj: property with a bank 200 feet hijrli. and at tlie lirown's Hill property near the town of Vou liet with a bank 2.")2 feet hih. He was al)le to remove riiii-<j:ravel without blastiu}; at the rate of (i.OOO cubic yards per 24 hours or 2 eul)ic \ar(ls per miner's incli per day. Some of tlie bottom <irouiid recpiired blastin<r and was moved at the i-ate of 10,000 cubic yards j)er day or cubic \ards per miner's im-h per da\', yieldinr .")! cents per cubic yard, accoidinjr to his rei>ort.

Mining cost was 7] cents ])er cubic yard, and stoi-a<;e in the Combie Ileservoir of the Nevada Irrijration District cost M cents jier cubic yard. Tailing:- from the Red Doij ]iro])erty was discharfxed to (Jreenhorn Creek tliroujih a tunnel tluit starts 70 feet above the creek and is 22 feet down in the bedrock at the mine. Pipe lines in use duriiiLr this period of opera- tion included one line 7()o feet lonjr of jipc 2(), 20, IS, and 15 inches in diameter. A second pipe line contained I,:}")!) feet of the same sizes of l)ipe. Nozzles used on the jriants were 7 inches and inches in diameter at the outlet. Because of difficulties with nuiddied water and conse- quent law-suits brou<;ht by Pacific (las & Electric Comjiany, coupled with the fact that the Nevada Irri<;ation District needs the remaining' sjiace in the C'ondjie Reservoir for tlie storage of water, it is doubtful that any further storaj;e of liydraulic tailing will be sold in this reservoir. How- ever, some consideration has been <;iven to raisin<i- this dam to provide additioiud space for the storage of hydraulic taiiiiif:-.

In H)40 the Wyandotte I)redj,Mn<r C'ompan\-, the San Carlos (iold Dredjrinjr Company, and the Pilot l)red:in<r Com])any operated di-aj:line di-ed<res to handle tailin*; from former hydraulic operations on (Ireen- liorn Creek. In 1945 tiie property was beinjr operated under a lease and option lield by I*hil P. Fredericks, Manx llotel, San Francisco.

Sec. IV] MINES BY COUXTIES 271

Placer County

IMaiiy important old placer luines are located at Dutch Flat, Gold Run. ]\Iiclii<ran Bhiff, Forest Hill, and other places in Placer County. Descriptions of many of them were published by Logan ip the Cali- fornia -Journal of Mines and Geolop-y for January, 1936. This publica- tion contains a lono; table of placer mines with references to older reports on them, and the reader is referred to that table for references to litera- tin-e on the older operations. The famous drift-mines of the Forest Hill Divide were described by Koss E. Browne - in State Mineralogist's Report X, for ]89(), and a good map and vertical sections accompanied the report. It is out of print but may be consulted in many libraries.

Below are a few notes on recent operations and on a few properties that are believed to contain reserves of possible commercial grade.

H.J. Aalders and W. W. Fraihcr of Lincoln operated a dragline dredge using a l|-cu.yd. bucket on the Gladding Ranch 4i miles north of Lincoln from January 1 to July 15, 19-40.

C. N. Chittenden of Lincoln operated a non-floating washing plant on the Rizzi Ranch from January 1 to July 20, 1940, and moved it to the Mulligan Ranch on August 1 where operations were continued until the end of 1940. The yield from 75,000 cubic yards of gravel was 222 ounces of gold and 45 ounces of silver, and from 26,000 cubic yards of gravel was 132 ounces of gold and 31 ounces of silver from the respective properties. In 1941 Chittenden operated a non-floating washing plant on the Johnson Ranch in the Lincoln district. Gravel was delivered by dragline excavator with a f-cu.yd. bucket. The yield from 43,500 cubic yards of gravel was 282 ounces of gold and 51 ounces of silver.

Duffy property, in sec. 3, T. 13 N., R. 11 E., and sec. 24, T. 13 N., R. 9 E., ]\r.D., and intermediate sections, is held by George L. Duffy of Forest Hill. Duffy states that he controls about 18 miles of mineral rights on the Middle Fork of American River either by options on patented ground or by special-use permits from U. S. Forest Service and the Federal Power Commission. The holdings are for a proposed dredging project and extend from the original Ruck-a-Chucky dam site to the mouth of the Rubicon River. The gravel has been sampled for a distance of miles from a point near the mouth of Volcano Canyon near the line between sec. 5 and sec. 6, T. 13 N., R. 11 E. and going down stream. Casing 11 inches in diameter was sunk at intervals of 100 to 250 feet. The holes were staggered, alternate ones being on opposite sides of the river: The depth ranged from 20 to 25 feet, and DufTy states that the average value in gold was 60 cents per cubic yard with gold figured at $35.00 per ounce. Width of the gravel is 350 to 400 feet. Eight miles at the lower end of the holding were sampled by means of sinking 70 caissons, 5 feet in diameter, by hand. Many of these did not reach bedrock, as it was possible to sink them to a depth of only 15 to 16 feet. Gravel was washed in a sluice and long tom, and according to Duffy gave a return of 32 cents per cubic yard. Gravel ig 500 to 700 feet wide on this lower end of the holding. Duffy states that early work

1 Logan, C. A., Gold mines of Placer County : California Jour. Mines and Geology, vol. 32, pp. 49-96, 1936.

2 Browne, Ross E., Tlie ancient river beds of the Forest Hill Divide: California Min. Bur., State Mineralogist's Kept. 10, pp. 435-405, I8I1O.

272 I'LA( Kit MIXINf; FOR GOLD IN CALIFORNIA [I>nll.l3r)

Oil the bars and in the rivor \vas done in circiilai- Tlic pits wcri- kept unwatered, and the jrravel was reiiM)ved by means of hydraulie ele- vators. Mueh of the jravel between these eircnhir pits was not distnrbed b.y this early method of mininj:.

A part of Dntfy's holdinjrs known as Horseshoe Bar in sees. 4, 5, T. 1: X., R. 11 E., was worked by AV. D. Inp:ram of Gridley with a drajiine dredge in 1041 and 1942. The wasliin<r plant was designed to serve a 5-cu.yd. dragline excavator, bnt the one aetnally in use was a Northwest drapfiine with a 2-eu.yd. bucket. Results from this operation are said to have been f?ood, but it was shut down by Limitation Order L-208 of the War Iroduction Board in 1942.

El Oro T)rcd(iinr) Coinpany of Colfax operated a drajjline dredjre on Indian Canyon in the Iowa Hill district from February 4 to September 19, 1940. A second dred'e was operated in Sliirttail Canyon from Au'ust

6 until October 31, 1940.

Gold Placers, Inc., 320 Capital National Bank Buildin*,'. Sacramento, operated a drayline dredjze on the Robinson Ranch in the Ophir district from April 30 to Aufiust 30, 1941, and on the Leak Ranch from September

7 to December 20, 1941.

Gold Recoveries Corporation, Box 58, Auburn, operated a dragline dredge on the William Ayers and Anderson property in the Ophir dis- trict during 1941.

Hallstrom and Lindblad, Route 7, Box 4343A, Sacramento, operated a non-floating washing i)lant, to which gravel was delivered by a dragline excavator with a l|-cu.yd. bucket, in the Ophir district during 1940. The yield at the liaker Ranch 6 miles east of Koseville from 124,000 cubic yards of gravel was 355 ounces of gold and 9 ounces of silver. The yield at property of the Placer Realty Corporation from 165,000 cubic yards of gravel was 471 ounces of gold and 30 ounces of silver. This firm continued operations in 1941 on the Joseph looney, ]\Iathilda Bahr, and Rogers Ranches and in Miners Ravine, all in the Ophir district.

W. 1). Ingram (see Duffy property also), Box 225, Foresthill, oper- ated a dragline dredge on Horseshoe Bar on the county line between El Dorado County and Placer County during 1941.

Innis Dredging Company, Nevada City, operated a dragline dredge on Dry Creek from January 1 to June 1, 1940.

Jasper-Stack Com pang (Recalp Company) of Lincoln worked out its ground in Auburn Ravine 2 miles east of Lincoln in May 1940. A dragline excavator with a 2-cu.yd. bucket was used.

Kaujield and McKinlcy, Box 274, Lincoln, operated a non-floating washing plant, using a mechanical excavator, on the liove Ranch in the Ophir district fr(m February 20 to June 2H, 1940.

La Kamp Bros, of Dutch Flat operated a non-floating washing plant at the Mutual mine in the Dutch Flat district during 1941. (1 ravel was delivered with a bulldozer.

Lebanon Consolidated Mines, 200 Bush Street, San Francisco, worked the Occidental drift mine in the Iowa Hill district from January 1 to December 31, 1941. The yield from 3766 cubic yards of gravel was 536 ounces of gold and 63 ounces of silver.

Sec. IV] MINES BY COUNTIES 27o

Lost Camp mine is a hydraulic mine of 440 acres 2 niileK by road from Blue Cauyon, at an elevation of 4:W() feet, iu sees. 22, 23, T. 1(5 N., R. 11 E., M. D. The t'hanuel contains interbedded layers of soft rhyolite tuff and fi-ee-washin Avhite (juartz gravel. Work on the prop- erty has proceeded at intervals over a lonjz period by three different methods, jjround sluicing, hydraidickin<r, and drifting. Several million cubic yards of gravel probably renuiin unworked, but little is known about the gold content.

The present owner is the Robie Estate, Wendell T. Robie, manager. Auburn, California, but the most recent work was done by a California corporation called Lost Camp Mining Company from 1934 to December 1941. The property includes water rights on Monumental and Fulda Creeks.

In 1944 a case was pending in the Sacramento Superior Court (No. 60474, Department 4). involviiig a complaint of Carmichael Irrigation District about muddy water discharged with tlie tailing from this mine. Stipulations limited the hydraulic season to the period from November 15 to April 30 of each year. This was a temporary arrangement which may be modified later. In this case McGeachin Placer Gold Mining Company and Mayflower Gravel Mining Company contend that the United States Debris Commission is a party in interest, because the tail- ing is impounded by a debris dam on the North Fork of the American River, and that the case should be tried in a Federal court.

In an entirely different suit in tlie Superior Court at Auburn, Lost Camp Mining Company was ousted from the property and the title confirmed to the Robie Estate. This suit involved a claim by the Cali- fornia Debris Commission of $4009.30 for tailing storage by the debris dam, but the Superior Court at Auburn excluded this point from the decision.

Mayflower Gravel Mining Conipa)ty, care of Richard Detert, Vlills Tower, San Francisco, holds a very large mining property at Foresthill now containing 5800 acres in sees. i5. 22, 23. 24, 25, 26, T. 14 N., R. 10 E., and including the following mining claims: Texas, Sacramento. Wash- ington, Garland Mill Slope, Excelsior, Hope, Tncle Sam, Green Spring, Live Oak, Small Hope, New Jersey (mineral rights). Brushy Slide, Dardanelles, Oro, and Adams pit.

The mine was first worked by hydraulicking. Tjater it was an important drift mine, working the .same channel as the bottom lead in the adjoining Paragon property. The priincipal production, about $1,600,000, was made between 1888 and 1899. The cemented gravel was crushed in a 20-stamp mill of 850-pound stamps, dropping ]()() tinies per minute. The battery screen was an iron plate punched with holes 0.2- inch in diameter, and the capacity was 6 J tons per .stamp-day. The gold was recovered by amalgamation. John Hays Hammond quotes the following figures: From December 11, 1888, to September 24, 1889, a total of 33,787 tons of gravel was mined from a length of 1620 feet of channel and yielded on crushing .$272,616.50 or $8.06 a ton.

The Mayflower operators worked downstream on the bottom oi- main lead to the boundarv of the Garland lill Slope claim (tlien under

''Hammond, John Hay.s, The auriferous gravels of ralifornia : California .Min. Bur., State Mineralogist's Rept. 9, p. 120, 1890.

274 I'LACKK MINIXC KOK liOl-D fALU'ORNIA [Bull.135

otluM- owiu'i'sliip), iis well as upst rcaiii lo tlu' ParaDU line. Tlio May- HowtM- <i:rt)uii(l contains an uiiworked souincnt of Uhio Load 1 miles Ion? inc'liidinji- tlioso inirts in tlio Excelsior and (larland .Mill Slope claims. Tlie bedrock tunnel of the layflower has been diiven ahead but must be driven an additional loOO feet to connect with the Ivxcelsior- Haltimore bedi'ock tunnel. When this connection is made the H-mile segment of channel Avill be drained. Water has been too troublesome in the i)ast.

Old re])orts desci'ibe an U])i)ei' lead in this same clianiiel which was worked in tiie i'araon mine. (Jeorjie DntVy of Forest hill did about a mile of drifting in several directions in the Mayllower shaft, 1")() feet above bedrock, about ]{);}8. His gravel averaged per ton with gold at .ji.'M i)er ounce. The south drift was the best and yielded to per ton from cemented gravel. Nuggets of to $!..')() were found.

He al.so did some i)raspeetiug in the old hydraulic-bank near the collar of the laytlower shaft by sinking five shafts ri.l feet apart, eacli about 20 feet dee]). The.se shafts represent the lower 20 feet of a !K)-foot depth of gravel and gave returns of $4..')() i)er cubic yard, according to Dutfy. He believes that this 90-foot depth could be dredged, liedrock is rhyolitic tutf". A segment of the Orono inter-volcanic channel. 2 miles long, extending from Mayflower bedi-ock tuniu>l southwai-d is supi)o.sed to exist in thi.s property.

Recent work has been done in the hydiaulic pit at Smith's Point and the Albright claim (sec. 27) ou a bank 4.")() feet high. A 22-mile ditch from Shirttail Canyon will carry aOOO miner's inches of water giving a head of r)2.> feet. Only 82.") feet of head has been used recentl.w A giant supi)lied by a 15-inch pipe uses 7- and it-inch nozzles.

McGeuchin Placer Gold Mining Conipanij has extensive holdings of placer gravel in sees. 2, 8, 4, 10, T. 14 X., K. 10 E.. M. 1).. near Iowa Hill. Several of these have been described by Logan"* under the names McGeachin Placer (Jold Mining Company, Morning Star drift mine, and Long Point Mining Company (Jupiter). C. H. Dunn, Sacramento, is president; 1. E. Rose, Iowa Hill, is maiuigei-. The pi-operty includes 1700 acres, (iround suitable for liydraulic mining is known as the Rig Dipper, which iiu'ludes the old Irish and Ryi'iie and Horman claims. Other claims include the Jupiter, Hazelroth. Schwab, Weber, and Winchester.

Water supi)l\ is obtained from Xorth Fork of Shirttail .Canyon and includes three ditches aiul the i\Iorniug Star reservoir 10 miles from the mine, which holds ISOO acre-feet. The main or McKee ditch carries li.jOO miner's inclies, and would furnish 400 feet of head at the mine if a 24()r)-foot penstock of Mi- and ;U-inth pipe were built. This ditch heads in .sec. 27\ T. 15 X.. R. 10 E. The Morninu- Star ditdi heads in sec. 18. T. 15 X., R. 11 E.

In connection with ])lans that were being made to resume hydraulic mining, a report was made in December li).'iS by F. II. Reynolds and Company. Consulting Engiiu'ei's, Saci-amento, and samples were taken by I. E. Ro.se. Sampling was done in old hydi-aulic banks roughly 50 feet in height aiul consisted of cuts 2 feet wide and 1 foot deej). Four of the sami)les were usetl in making calculations of gold-content. and a fifth was discarded because it had been taken near bedrock, and

I.oBan, C. A., op. cit., 193G.

See. IV]

Minks By Cotntiks

Fio. 85. Sampling: hydraulir liaiik r>() tVt-t liih (ompany. Phola bii (nitrtisii

tlie gold-content was lii<rli. Ko.se tliinks tluil 1 he iiduiul contains 'i.l.OOO.- 000 to 30,000,000 enbie yards of rravel witli.nt oveihnrdcn tliat will yield 20 cents per enbic yard in gold, in a i-onglily circular area :i")()0 feet long and more than 2{)()() feet wide. Additional >ai-dage is avail- able with overburden. Kose states that !..')( )().()()() cubic .vai-ds have already been worked on the Irish and l>yrue claim, and .l.OOO.OOO lit ().000,600 cubic yards on the Ilorman. JJanks range from 40 1o 2.') feet in height. Kose states that drifting oi)erations cai-ried on for 2 years recently yielded gravel miming from M' to per cubic yard in gold.

H. . McKinehj of Newcastle operated a dragliue ili-edge ou the Fisher Ranch in the Ophir district from -lune 17 to .Iul\- :'>1. 1!I41.

Midland Company, Inc., Box 8. Sawyers IJar, moved its dragline dredge from the Lincoln district to the North Fork of Salmon River in Siskiyou County during 1940. The dragline exeavatoi- had a 1 j-cn.yd. bucket.

Panoh Gold Dredging Coinjxnn/. IJox SiKi. Liucohi. opeiated two dry-land outfits on the Forsyth and Jewis and (i. E. Stoll ]n-oi)prties

270 I'LACKK MtNlNC lOU COM) CAr.IKOKNIA 1 >lll I. 1 n.')

liiriii;r 1!40. Kroiii M;ir-li to Octohcr HUl this conipaiiy oiu'i-atcd a nou-floatiii wasliiiijr plant on tli.' Fci-i-ari property in tlie Opiiir district, (iravcl was delivered ly a dca-j-Iiiie excavator with a 11-cn.yd. biieket to a washing- i)lant ecpiipped witli Ainlay howls. The opera- tion at the Korsyth and Lewis property was continned dnrinr 1!)41.

Pautlc Bros, of Lincoln operated a dry-land placer machine eciuip- jx'd with fonr Aiiday bowls on the Ahart. Ferreva, and Kaneko Uanches in the Ijincoln district duriny; 1!)4(). The yield from ]7i),8()() cubic yards of rravel was ():{2 onnces of jrold and 111 onnces of silver. The rravel was delivered with a 1-cn.yd. drajrline excavator.

I'amijun inliu, in sees.. l:{, 18, 19, :{0, 31, T. 14 N., K. 11 K., and .sec. 24, T. 14 X., K. 10 E., M. D., is one of tlie large hydranlic mines of the Forest Hill distriet 2 miles from Foresthill at a i)laee formerly called Hath. Loian '' published two pajres of description of this mine in State Mineralo-iist 's Report XXXIl., and that descrii)tion is up to date with a few exceptions, as follows: I'arajion Mines. Inc., W. K. Wilson, president, Foresthill, has acciuired the lease and option form- erly held by Alanta Mines, inc.. of which Kiiij: (I. (Jillette was i)resi- dent. The property now contains 17()() acres owned by the .1. F. Thomp- .son Estate, of which Charles II. Sejrerstrom, Sonora, is administrator. Wilson states that an old tunnel that was driven through the hydraulic bank to carry the water-ditch contaijied leaks that probably helped to eau.se a serious cave at the jiro])erty in 1 He has abandoned this tunnel and moved the forebay and ju])e-lines to the ea.st side of pit.

Rosci'illc Gold l)r(<hjiu(j Compuiiy, Mol California Street, San Fran- cisco, operated a dredge in Strap Ravine (i miles east of Koseville from January 2:} to the end of lf40. The dredge was driven by electric powei' and had a bucketline of seventy-two .'{-cu.ft. buckets. This opera- tion was continued during ]f>41.

IStewart Grarcl Mines, c/o -I. I). Stewart, LJS Conunercial Street, Aubui'ii. controls al)out aeies on the great Eocene river chanmd that pas.ses through Dutch I'Mat and (lold Kun. The |)r()perty is in sees. 2, :i, 4, !), 10, T. IT) X.. K. 10 E.. M.I)., and covers a length along the channel of 2 miles.

It is cons)icuous because highway no. 40, the main route from Cali- fornia to Truckee and Reno, runs for a mile at the base of one of the old hydraulic baidis nearly 200 feet high. The main line of the Southern Pacific Railroad is at the top of this old hydraulic face. The channel is li mile.s wide at thi.s point and the gravel was origiiuilly oOO feet deep in the middle of the channel, .so a depth of several hundred feet remains unvvorked. According to Stewart, a length of 11, ")()() feet south of the highway has not been drifted on bedrock.

The mine is provided with a 4000- foot bedrock tunnel in green- stone, which reijuii-es no timbering. The p<irtal of this is 17) feet higher in elevation than Canyon Creek, and this ci-eek empties into Xorth Fork of American River. The tunnel is driven on a grade of three-(|uarters of an inch per foot, and during hydraulicking operations it was provided with a sluice and steel rails for riffles to recover the gold. Tailing was discharged to C'anyon Cieek.

Logan, C. A., op. tit.

Sec. IV] MINKS BY COUNTIES 277

The south end of the property for a lenjith of about half a mile and width in the bottom of 400 to 1200 feet has been worked to bedrock by means of hydraulic mining. The lower 60 to 80 feet of the gravel is cemented and required blastiji? in advance of hydraulicking:. After hydraulic mining ceased the property was worked by drifting and a tunnel was driven 1800 feet on the bedrock beyond the 4000-foot tunnel, which is at a lower elevation, to give access for drift-mining. Logan " has published details on production during short periods from 1872 to 1879 in State Mineralogist's Report XXXII.

To the north of the railroad, on the part of the channel that drains toward Bear River, are many millions of cubic yards of unworked gravel in the Dutch Flat district. Extensive deposits in this area are owned by James L. Gould, Soda Springs P. O., Placer County, and Nichols Estate Company, c/o Arthur Nichols, 846 Mendocino Avenue, Berkeley. Individual menibers of the Nichols family hold tracts in this vicinity also.

Volcano Miyiing Company, Ltd., 1018 Mills Building, San Francisco, worked the Volcano drift mine in sees. 18, 19, 20, T. 14 N., R. 11 E., M.D. between Foresthill and Michigan Bluflf in 1940. The operation was continued in 1941, and 4000 tons of gravel yielded 206 ounces of gold and 27 ounces of silver.

Plumas County

Tlie mineral resources of Plumas County were described in the California Journal of Mines and Geology for April, 1937, which con- tains a geologic map of the county showing the locations of the principal mines and a long table of mines giving references to earlier reports. Placer mining was not active in the county in 1937, and only a few such mines are described. Descriptions of many of the old drift and hydraulic mines are contained in the chapter on Plumas County of State Mineralogist's Report XVI. which is still available at this time (1945). A map showing drift and hydraulic mines of La Porte district is on file at the San Francisco office of this division.

Baker amd McCowan, Box 305, Chico, moved a dragline dredge from Butte County to Meadow Valley in the Quincy district and operated from August to December, 1940 and during 1941. The dragline excavator had a 1-cu.yd. bucket.

Innis Dredging Companjf of Nevada City moved its dragline dredge from Nevada County to Lights Creek in the Lights Canyon district and resumed operations August 4, 1940. The dragline excavator had a 2-cu.yd. bucket. In 1941 this operation was continued from elanuary 1 to September 22, and the yield from 250,000 cubic yards of gravel was 1653 ounces of gold and 130 ounces of silver.

Lohicassa Company, Box 812, Sacramento, operated a dragline dredge on Jamison Creek in the Johnsville district from August 20 to December 24, 1941.

" Logan, C. A., (Jold niine.s of Placer County, tJold Kun di.strict : California Jour. Mines and Geology, vol. 32, pp. 62, 63.

See also : Dutch Flat District, pp. 56-58.

Averill, C. V., Mineral resources of Plumas County : California Jour. Mines and Geology, vol. 33, pp. 79-143, 1937.

MacBoyle, Errol, Mines and mineral resources of Plumas County : California Min. Bur., State Mineralogists Rept. 16, p. 188. 1920.

278 I'LACKK MININO FOR (SOLD IN CALIFORNIA [Bull. 135

SACRAMENTO COUNTY Natomas Company

Natomas Company. Fonmi Inildinjir, Sacramento, vas the larfjest prodncer of placet- 'old in Calif oi'iiia in both 1!U() and 1!)41. Durin<r those years the company operated seven (lri'd<res in the Folsom district. Operations wci-e curtailed in 1!>42, lf)4.S, and 1!)44, hut were heinj; iiici-eased a<j:ain in the summer of 1!)4"). One of tlie dred<res is e(iuipi)ed with buckets holdiiifr 17 cubic feet each, two with 16-cu.ft. buckets, three with 12-cu.ft. buckets, and one with 9-cu.ft. buckets. The dejith whicli they can difj beh)w the surface of the water ranjxes from 80 feet to 70 feet. Bedrock is volcanic ash. More <;ravel e.xists below the vol- canic ash in parts of tlie dred<rinjr field, but it is not jrold-bearing. Thomas McC'ormack of Rio Vista is ])resident, and R. O. Smith of Nato- mas i.s fjeneral mana<rer of jrold dred<;injj:. This company desi<rns and builds its own dredges, and the following: notes on recent practices have been supplied by R. G. Smith:

Mdin Drirc. Tiie main drive of the bucket line has been diaufred to direct current (d-c) motors witli Ward-Leonard controls. Tiie drive is throujjh reduction <;ears wliich are entirely enclosed in cases. The reason for this is the moi-e efficieiit variable speed and the j?reater ea.se of control. Because of this, the company has been able to increase bucket-line speeds as much as 50 jiercent where the {gravel is not too hard. To supply the dii-ect current a motor prenerator set is installed in the bottom of tiie hull. Many of the controls for other machinery ai-e installed in the same room. This helps to maintain the center of frravity of the drediie at a low ])oint. Other new drives for main bucket line, used by different companies consist of two-motor alternatiiif; curi-ent drives with either constant or variable speeds tln-ou<rh \'-belt di-ives to the main drive shaft ; also a sin<:le two-speed motor drive through V-belts to the sinji:le main drive shaft of the ohl-type conventional drive.

Ladder Hoist. AVhere motors have been installed for tii(> main drive, it has become necessary to have a separate ladder hoist. The.se are driven throujjh enclosed fears and are jrenerally ojKM-ated with i-ei;enerative brakiii. The hoist is e(piipped Avith ma<j:netic brakes and post or <;ravity brakes operated i)nennatically ; also with T;illy over-speed and over-haul control. Greatly increased hoistinj? speed has been adojted.

Swing Winch. Where motor generator .sets have been installed for d-e main drives, individual bow-liiu' winches driven by d-c motors have been installed. They are driven throu;h enclosed reduction fiears and are equi})ped with AVard-Leonard controls. This jives efficient variable speed and maximum <'ase of contr-ol foi- thi' side-swiufjr. Line ti-avel on both sides of the dred<:e is made the same. N'ariations of (his pi'actice have consisted of usinj; a-c drive a.s hei-etofore, i.s()]alini- the bow-line drums to operate without fioiufr thi-onih a chain of jrears on the side-line winch. The side-line winch is used as drive for one bow-line and a separate winch and motor are used for the other bow-line. Most of these installations are ecjuipped with pneumatic control for both sliifting of frictions and for brakes. Brakes are usually of the f;ravity type, which are released by the i)re.ssnre of com]ire.s.sed air.

Side-Line Wineli. Pneumatic control of both brakes and frictions has become frencial i)ractice, and the winches are driven by enclosed

Sec. I\'J Ml\i:s 15V coiXTiKS 279

reduction ciirs. Tlie use of i)iieun]atic control for tlie winches has done nway witli the j-reat inimber of operatinji- levers Avhicli formerly had to he placed to one side of the bucket-line. Now the winch room can be placed on tlie loupitudinal center-line of the dredjze, and this jrives the operator a much better chance to see Avhat he is doinpr. Pneumatic con- trol reduces the manual effort i"e<juired of the operator to a minimum.

Screen Di'tn . Screens are now driven either directly throu<rh ciu-losed reduction carina' set in the same line with screen or with V-belt drive with motor set on a horizontal plane.

(loUl Savinfj. The tendency has been to increase the total width of .i:()l<l-savin<i' devices per cubic yard handled rather than to increase the total area. The total width of riffle-tables has been divided into nar- rower sluices, and this tends to increase the effective riffle area. The reason is that a tiltinji of the di-edjie in the lonjiitudinal direction giving a fore and aft pitch, tends to thi-ow all the fluid in the sluices to one side of the sluices. If the sluice is kept narrow, this tilting is not likely to expose the riffles on the high side of the sluice. Xatomas Company ha.s used jigs on some of its dredges since 1914. Where a jig 42 inches wide is used, the riffle sluices are made 21 inches wide. This is in contrast to a 8()-inch width formerly used. On the Natomas dredges on Avhich jigs are n.sed only a launder is placed between the distributor box beneath the screen and the jig, that is, no riffles are u.sed ahead of the jig. The niain consideration for the use of jigs is that the gold is difficult to anuilgamate. Two of the dredges of Xatomas Company are not equipped with jigs because the gold which they recover is not tarnished. Jigs may be able to save fine gold a little better than riffle sluices as ordinarily handled. Xatomas uses both Bendelari and Pan-American jigs. On the Boulelari jig the agitation is effected by an eccentric which actuates a circular rubber diaphram in the hutch. On the Pan-American jig the whole bottom of the jig is moved up and down by an eccentric, and the joint between the .stationary and the moving part of the hutch is a circular rubber part shaped like a tire-casing. Jigs need a thicker pulp than riffles. Too much water will carry the gold past the jigs. Hence only the high-pressure water goes over the jigs, and an equal amount

1 Made by I'an-Anierlcun Engineering Company, S20 Park r Street, Berkeley, California.

280 PLACER MININ(1 FOR OOLD IN CALIFORNIA [Bull. 135

of low-pressure water is added below the jifrs. On a dredge handling 500 to 600 fubic yards per hour, of which 40 percent goes to the gold- saving devices. (iOOO gallons per minute of high-pressure water is used and HOOO gallons per minute of low-pressure water. An arrangement that is (piitc connnon is to use a single-ceil jig as a rougher, with riffle sluices below the jig to take the overflow and to serve as emergency gold- saving e(juipment. The concentrates are amalgamated on riffles and then put over a cleaner jig, from which final concentrates flow to a ball-mill for .scouring the rusty gold. A variation consists of some riffle tables ahead of the jig.s and also of amalgamation of the jig concentrate in a continuous barrel amalgamator. Another arrangement consists of two-cell jigs with no riffles on the jig overflow. Concentrates are either subjecteil to riffle amalgamation or fed directly to cleaner jigs. The final pr()d\ict is then amalgamated.

Hull Construction. Although some of the recently -built dredges have been e(|uipped with the conventional riveted steel hull, the tendency toward wcltled construction has been evident. Pontoon-type hulls have met with considerable favor even for dredges of 9 cubic feet and under, and for digging to depths up to 70 feet. The pontoons are of welded con.st ruction and are bolted together during assembly in the field. Hulls with welded construction have been in service for several years without any evidence of failure.

Buckets. Rivetless bucket lips have been coming into greater favor rapidly. Perfection of small construction details and the operating advantages gained have been contributing factors to popularity. Low lij)s tiiat are welded to the bucket are coming into use in some places, but not yet in California.

R. G. Smith points out that a dredge should be tailor-made to fit the particular tract of ground that is to be worked. The design of the dredge must take into consideration each of the following:

1. Depth of the gravel.

2. Whether the gravel is tight or loose.

3. Whether large boulders are present.

4. Whether there is a high percentage of sand and silt.

5. Length of time that the dredge is expected to last.

On one Natomas dredge the fines from the riffle sluices go to a sump containing a revolving sand-wheel. Buckets around the circumference of this wheel pick up the sand from the sump and discharge it to the same stacker that carries the oversize from the trommel. Silt overflows from the first sump to a second sump, where it is picked up by a purap and discharged through a pipeline that runs along the side of the stacker.

Other Operators

Capital Dredging Company, 351 California Street, San Francisco, operated two connected-bucket dredges on its property 5 miles south of Folsom throughout 1940. 1941, and until October 15, 1942. One dredge had 88 and the other 100 buckets of 18-cu.ft. capacity. They were both electrically driven.

Carson Creek l)rc(l</in<j Company, 21(i Pine Street, San Francisco, wa.shed gravel on the Martin Quinn Estate from September 11 until the end of 1940, using a dragline excavator with a IJ-eu.yd. bucket. The

Sec. IV] MINES BY COUNTIES 281

operation was continuecl from Jaimary 1 until February 5, 1941, and was then taken over by Northwest Development Company.

Climax Dredging Company of Folsom operated a dragline dredge on the J. Vincent property in the Folsom district from January 1 to April 8,1941.

Cosunincs Gold Dredging Company, 351 California Street, San Francisco, operated a connected-bucket dredge in the Cosumnes River district, 7 miles southwest of Sloughhouse during 1940, 1941, and until October 20, 1942. The dredge is equipped with 63 buckets of 12-cu.ft. capacity, and is electrically driven.

Cutter and Mueller recovered gold as a by-product in the operation of a commercial sand and gravel plant at Fair Oaks in 1942. The recovery from 40,320 cubic yards of gravel was 183 ounces of gold and 15 ounces of silver.

General Dredging Corporation of Natoma or 811 W. 7th Street, Los Angeles, operated a dragline dredge on the American River in the Folsom district during nearly all of 1940. This corporation was dissolved Sep- tember 30, 1941, but continued to operate as General Dredging Company, a partnership. Dredge no. 1, equipped with a dragline excavator having a 5-cu.yd. bucket, was operated on American River. Dredge no. 2, oper- ating on the ancient river channel in the same district, used a dragline excavator with a 2-cu.yd. bucket. Dredge no. 4, working gravel along the American River near Fair Oaks, also used a dragline excavator with a 2-cu.yd. bucket. Operations were continued in 1942.

Hoosier Gulch Placers, 1015 25th Street, Sacramento, operated a dragline dredge on Katesville Gulch and on the Logtown property in the Cosumnes River district during 1941. The dragline excavator had a 2-cu.yd. bucket. A second dragline dredge served by a 2-cu.yd. bucket was operated on the Hutchison property from January 5 to October 31, 1940. This company operated boat no. 1 on the Biggs Ranch and boat no. 2 on the Rossi property throughout 1941 and during part of 1942.

Humplireys Gold Corporation, 910 First National Bank Building, Denver, Colorado, operated a dragline dredge in the Cosumnes River district on the Fassett-Parker-Hanlon property from January 1 to Decem- ber 5, 1940. The equipment, which included a dragline excavator with a 2i-cu.yd. bucket, was then moved to the Hutchison property where operations were continued during all of 1941 and from January 1 to April 6, 1942. In 1942 the floating washing plant was served by four dragline excavators, each equipped a 2i-cu.yd. bucket. These were used to strip overburden as well as to deliver auriferous gravel to the plant.

Lancha Tlann Gold Dredging Company, La Lomita Rancho, Locke- ford, operated a connected-bucket dredge at Sailors Bar, American River, from April 20, 1940 until November 11, 1942. The dredge is equipped with 84 buckets of 6-cu.ft. capacity and is electrically driven.

Lohicassa Company, Box 812, Sacramento, operated a dragline dredge, with a 1-cu.yd. bucket on the Mahon property from June 5 to October 17, 1940, when the property was worked out.

McQueen and Downing, 1040 38th Street, Sacramento, operated a dragline dredg on Deer Creek in the Folsom district from September 10 until December 17, 1940 and from January 1 to February 14, 1941.

Natomas Company. See page 278.

2fi2 PLACKK MINIXC I'OH f;()[,I) IN (AI.II'OHMA [ 1)11 1 1 . 1

Pdcijic Const Aijiivi (jnlis. Inc., 1401 4'Jiul Street, Saei-jiiueiito. reeovered 111 ounces of old and 11 oinu-es of silver as a b-prodiict in the operation of a commercial sand and n-avel iilant at Fair Oaks in 1042. In lf>4."{ this com]>any, tojrether with Fair Oaks (Jravel Company, reeovered 240 onnces of rojd and 21 ounces of silver.

San Bernardino County

The minei-al resonrccs of San I'.crnardino Coimfy liaxc been described by Tnckei- and Saiupsoii ' in the California .loui'iial of Mines and (leoiojry for October 104:}. Althoiijih this connly contains a wide variety of mineral de])osits of commercial importance, and althonjrh the repoi-t cited contains descriptions of many lode-jzold mines, little i)lacer miniiifr for old lias been done in the connt\' recently.

If()( fli)if/ Bros., ]>ox 768, Sacramento, recovered i)lacer old as a b\-|)rodiict of an opei-ation carried on throiijihont 104.'{ principally for scheelite at the Patcli mine in the Randsbnrjr district, (iravel amoniitiii".!- to "jUT.liif) cubic yards was mined Avith a drajiline excavator, of which 1:U,9;U cubic yards wiM'e trucked to a stationary washing: ]ilant. The l)y-product production of iii-ecioiis metals was 210 ounces of <i<)ld and 45 ounces of silver.

Ilolconih Vallcif Phiccr Conipduy, 91-i Xortli Nfain Street, Los An<ieles, opei-ated a non-flf)atin<i' wa.shinjr i)lant in the llolcond) Valley disti-ict, to which pi-avel was delivered by tractor and scraper from July 7 to Xoveml)er 1(), 1041. Tlie yield from lfi,2(jr) eubic yards of {jravel was 204 ounces oC jiold and 10 ounces of silver.

San Joaquin County

('(ilifi>nii/i (I'old /iiKj Conipaiin, '.i'A California Street. San Francisco, operated an elect-ic connected-bucket drodjie witli 81 buckets of ()-cii.ft. capacity dnrin<>: 1040 and 1041. in the Jenny Tiind di.strict.

(iold If ill Drxhjituj Coinjxnnf, :}11 California Street, San Francisco, operated two electric connected-bucket dred<ies on tlie Jenny Lucas, Alex IN'iie. Putnam. Tliorne, and Osterman properties in the Camanehe dis- li-ict dnrintr 1041. Some work was done in San Joafpiin County duriiifr li40 also. One dredje had (56 buckets of I'j cu.ft. capacity and the other had 87 buckets of 8J-eu.ft. capacity. Operations wei-e continued in 1042 on some of the properties mentioned above and also on property of Cali- foi-nia liands, inc. and Central ]>ank of Calaveras duriiifr most of 1042. The company also ojierated one dred;:e at a time during' i)arts of 104:}.

(iohl V(ill< If Dredging ConijKiny operated a diy-land washing plant to which jrravel was delivered by jrasoline dra<:line excavator with a J-cn.yd. bucket at tlu' IMurdock Kanch in the Camandu' district from February 2.') to May 24, 1042. The yield fnmi 0,:n6 cubic yards of ;ravel was 8:{ ounces of }rold and 6 ounces of silver.

Lohicdssa Companif, Box 812, Sacramento, operated a dra<:line dredre usin*; a IJ-cu.yd. l)ucket on the Foster Ranch in the Camanehe district from January 1 to Fay 14, 1042. The property was then aban- (h)ned as worked out.

MohdniniK Sdiid (iiid drard f'oiii pditg, 7)21 East Lodi Avenue, Lodi, l)rodnced a small (piantity of <rold as a bv-]>roduct in pi-eparing sand and Travel for concrete ar{rrep:ate durinjr 104.'i.

' TucUtT, W. n., and Sampson, It. J., Mineral re."<ources of .San J'lrnardino County: Califurnia .lour. Mines and Geology, vol. 3;t, pp. 427-549, 1943.

Sec. IV] MINES BY COUNTIES 283

San Griico Compayxy and C. E.Grnwell of Angels Camp operated drajirline dredges on the IMcGurk property in the Bellota (Linden) dis- trict in 1940. Each operator used a dragline excavator with a l|-cu.yd. bucket.

Smith-N otterman Company, 245 West Rose Street, San Francisco, operated a dragline dredge with a l|-cu.yd. bucket on the Elmer Cady and Lewallen Ranches in the Jenny Lind (Bellota, Linden) district during 194L The operation was continued in 1942 from January to March 26, and the yield from 93,105 cubic yards of gravel was 344 ounces of gold and 14 ounces of silver.

A. G. WatJxins & Sons of Linden operated a dragline dredge equipped with a 2-cu.yd. bucket during 1940 and parts of 1941 on the Calaveras River.

Shasta County

A report on the mineral resources of Sha.sta County was published in the California Journal of Mines and Geology for April 1939, and a map of the county .shoAving locations of mines was included; also a table of mines giving references to older reports. All of the placer operations mentioned below were started after that report was written. A few earlier operations of similar nature are described in the April 1939 Journal.

B. H. K. Mines, Box 325, Orland, operated a dragline dredge equipped with a l-cu.yd. bucket on the R. C. Connelly and Robert Litsch properties on Clear Creek from November 15 to December 31, 1941. The yield from 54.400 cubic yards of gravel Avas 339 ounces of gold and 48 ounces of silver. The operation was continued from January 1 to May 15, 1942, and the yield from 120,000 cubic yards of gravel was 760 ounces of gold and 104 ounces of silver.

/. P. Brennan, 1343 Butte Street, Redding, operated a dragline dredge on Tadpole Creek from January 1 until October 7, 1940, then moved the equipment to Champion Gulch and continued the operation until Jitne 1941. Both of these operations were in the Igo district. The dragline excavator was equipped with a l.j-cu.yd. bucket.

Clear Creek Dredging Company, Box 598, Redding, operated a drag- line dredge using a IJ-cu.yd. bucket on Clear Creek in 1940. In 1941 a second dredge a 2|-cu.yd. bucket was added. This company operated in 1942 also.

Columhia Construction Company, 1522 Latham Square Building, Oakland, prepared 1,781,466 tons of gravel to be used in the construction of Shasta Dam from a point upon the Sacramento River near Redding in 1940 and recovered a substantial quantity of gold. In 1941 this com- pany prepared 4,038,167 tons of gravel and recovered 2810 ounces of gold and 301 ounces of silver as a by-product. Two dragline excavators were used, one with a 5-cu.yd. bucket and the other with an 8-cu.yd. bucket. In 1943 the company produced 1,500,000 cubic yards of sand and gravel and recovered 1555 ounces of gold and 166 ounces of silver as a by-product.

Crow Creek Dredging Company, Box 558, Redding, operated a dragline dredge on Crow Creek in the Igo district intermittently during

lAverill, C. V., Mineral resourcts of Sha.sta County: California Jour. Mines and Geology, vol. 35, pp. 108-191, 1939.

See also Averill, C. V., Gold dredging in Shasta, Siskiyou, and Trinity Counties : California Jour. Mines and Geology, vol. 34, pp. 96-125, 1938.

I'LACLR MINlNf; KOR OOIJ) IN CALIFORNIA

I Hull. l.'M

1940. Durinp: lf)41. 22().()0() cubic- yards of <i:ravpl wore delivered by a drap:line excavator with a IJ-cu.yd. bucket and were washed. In lf)42 operations continued on Cottonwood Creek from January 1 to April 13, and 100.000 cubic yards of grave! yielded 580 ounces of j;old and 20 ounce.s of silver.

DcKarr and Herbert of Reddinjr operated a drajjiine dredje, usinf? a 3-cu.yd. bucket, on the Fred Kohle f)roperty on North Cow Creek from January 16 to March 17, lf141. The yield from 2:},8()0 cubic yards of gravel was 207 ounces of pold and 46 ounces of silver.

Dobbin Gulch I)redgin<j Conijxmy, Hox )'-V.), ledding, operated a dragline dredge with a 1 |-cu.yd. bucket, on the Montgomery property on 4<'lat Creek from January I'to May 80. 1!)41 . The yield from 142,160 cubic yards of gravel was S'S ounces of gold and ()2 ounces of silver. In 1942 operations were conducted on the Roaring River from March 3 to June 2. The yield from 70,r)0() cubic yards of gravel was 169 ounces of gold and 11 ounces of silver.

Finch Gulch Dredging Cunipani), 2404 Russ Building. San Fran- cisco, in.stalled a connected-bucket di-edge eriuipped with 76 buckets of 4-cu.ft. capacity on Clear Creek near French (Julch and began opera- tions on September 2. 1940. The operation was continued during 1941.

C. E. Gruwcll, Hotel Redding, Redding, operated a dragline dredge on the Fish, Forschler, Rais. and Russell Ranches in the Igo district duriiig 1941.

Lincoln Gold Dredging Contpang of Lincolr. operated a dragline dredge having a 2-cu.yd. bucket on the Jii-ady ])r()perty in the Igo dis- trict in 1942. The yield from 87,284 cubic 'yards of' gravel was 162 ounces of gold and 26 ounces of silver.

R. S. Olaon, 1178 Walnut Avenue, Redding, operated a dragline dredge from January 1 to March 10, 1940, on Chiiia (Julch and from June 18 to December 5 on Daly dulch. P>oth are in the Igo district. Operations on Daly Gulch were continued in 1941.

Pioneer Dredging Conipong, Box 80.1, Redding, opeiated a dragline dredge ecjuipped with a 8-cu.vd. bucket, in Happy Valley from Jainiarv I to 'August 21, 1940.

.

U :

M

|hi

r

1 :

Roc. rv

Minks By Cocxtiks

28f

Snu (iruco (\jnijiiinif, Koddiiij, moved its dra<!:liiu' dred{:?e equipped with a n-cu.yd. bucket to property of the Happy ValU?y Land and Water Company and op(>rat('d from Xovember 1 until the end of 1940; also during; IfUl.

Tehama Drcdfjiny Company, l>ox 727, Anderson, oj)erated a drag- line drede. wliieh had a v(*-yd. bucket, at the Gold Acres mine near (ias IV)int from larcli 20 to June .30, 1941. The yield from 48,860 cubic yards of gravel was 242 ounces of gold and 17 ounces of silver.

Thurman Gold Dredging Company, 235 ]\Iontgomery Street, San Francisco, installed a connected-bucket dredge equipped with 72 buckets of 9-cu.ft. capacity on Clear Creek and began operations on December 1, 1940. Operations continued during 1941 and until October 14, 1942. SIERRA COUNTY

Depot Hill hydraulic mine owned by F. J. Joubert of Campton- ville lias been operated practically every season for many years. Stor- age for the tailing is available behind the Rullards Bar dam of the Pacific (Jas & Electric Company. The mine is o miles north of Campton- ville on the .state highway nnming to Downieville in .sec. 19, T. 19 N.. K. !) E., ]\I. D. ]\Iore than a page of additional details about this mine is contained in the California Journal of Mines and Geologv for Janu- ary 1942.1

Indian Hill )nine was described by Gardner and Johnson as follows :

B. F. Dyer operated the old Indian Hill mine near Camptonville during 1931 and 1932. Tlie material washed up to the end of 1932 con- sisted maiidy of slides from the faces of the old w'orkings. The gravel deposit was 35 feet thick ; the grade of bedrock was 1 inch to the foot.

' Averill, (". V., Mines and mineral re.'oince.s of Sierra Countv : California Jour. Mines and Oeolopry, vol. .''.8, p. 29, 1942.

-c.ardner. E. D.. and John.son, C. H., Placer mining in the western United States, I'art II, HydrauiicUinfi. etc. : r..S. I'.ur. Mine.' Inf. fire. (;7S7, i)p. 1934.

Depot Hill hydraulic mine. Reprinted from California Journal of Mines and Geology, January ii'Ji, p. Zi.

rLA( KR MIMN(! FOR OOLO IX CALIFORNIA [Bull. 135

KiG. S!i. I'oviTty Hill I'ropifties lunlcr construction. h'citrinlrd ftotti (Utli- loriiifi ./oiiriKil of Miiiir. luid (!iiiUi<i\i. Jdiiiiari/ lH'iJ, p. -Ui.

Hi. ;tO. JU-nioMhn ov.rl.uidcM Amador County. J'hoiii bx

iiivlcNii ')) y((b(t .Mdintliicl iir>u(/ Vo)ii])(iiiy.

Fig. 91. Willlatn RichUr and Sons diapline dredge. Reprinted from California Journal of Mines and Geology, January 19k2, p. 38.

See. IV] MINKS nv counties 287

Water was brought to llie luiiit' tlir()U<ili a !>-inile ditch and 3000 feet of 22-iiK'h and 1500 feet of la-incli iiipc The head was 130 feet. One No. 6 giant with a 4-, 4|l-, or (i-ineli nozzle was used. Boulder.s up to 14 inches in diameter were run tln-oujili tlie sluice boxes. The sluiceway was down a narrow gulch and consisted of .six sections of boxes (2 to 6 boxes to the section) and the rock bottom of the gulch between sections. There was a drop of 10 or 15 feet at the end of each section of boxes. The fall and cascading down the rocky gulch between each section broke up all cemented material and washed the gravel free of clay.

The boxes were 40 inches wide and 40 inches high ; the grade was i-inch to the foot. The upper five sections of boxes were paved yith wooden blocks; the riffles in. the lower section Avere of rock paving. Seventy percent of the gold was caught in the upper two boxes. Three undercurrents were used near the lower end of the line. The discharge of one luidercurrent went into the main sluice before the next was taken out. The grizzly opening for an undercurrent in the bottom of the main sluice was 18 by 40 inches. The grizzlies were of 1- by 3-inch iron bars set on edge inches center to center. Additional top water Avas run over the undercurrents from an opening in the side of the sluice. The. first undercurrent was 8 feet Avide by 24 feet long. The riffles consisted of rows of pine blocks 6 inches thick by 6J inches deep separated by H-inch crossboards. The second undercurrent was 8 feet Avide and 20 feet long. The riffles consisted of 31- by 3i-inch angle iron -J inches thick and set crossAvise on 5-inch centers. The third undercurrent at the end of the loAvest box Avas 10 by 12 feet. The riffles Avere four angle irons 1 inch apart at the head of the undercurrent and rock paving from there doAvn. A crew consisted of seven or eight men. About 100,000 cubic yards Avas Avashed during the 1932 season at a cost of 8 cents per cubic yard exclusive of con.struction Avork.

Loftus Blue Lead Mining Company, 801 Columbia Street, South Pasadena, operated a hydraulic mine in 1940 and 1941 on a large group of claims running from St. Louis to HoAvland Flat, a distance of 4 miles bv road, in sees. 31, 32. T. 22 N., R. 10 E., M. D. ; sees. 5, 6, 7, T. 21 N., 11. 10 E. ; and sec. 12, T. 21 N., R. 9 E. In 1940 the yield from 60,000 cubic yards of gravel Avas 352 ounces of gold and 25 ounces of sih'er. A few additional details about this mine are contained in the California Journal of ]\Iines and Geology for January 1942.

Pioneer Project mine in sees. 13, 14. 23, 24, T. 21 X., R. 9 E., M. D., is a consolidati(m of the old Pioneer Avith the adjoining Comet, Chal- lenge, and Riffle claims. It Avas Avorked in 1942 and 1943 by A. J. Just, AV. II. Pike, and A. J. ]\Iodglin of LaPorte. Hydraulic operations for a period of 10 days in 1942 yielded 71 ounces of gold and 4 ounces of silver from 17,000 cubic yards of gravel. A sub.stantial quantity of gold Avas recovered during a 3-month period of operation in 1943.

Poverty Hill Properties, 974 INIills Building, San Francisco, is a lartnership of Avhich the general partners are A. J. Oyster, W. C. Van Fleet, Walter W. Johnson. Operations Avere conducted in 1940-41 on a part of the main La Porte channel, one of the old Eocene auriferous channels. The property consisted of 1100 acres in sec. 32, T. 21 N., R. 9 E., :M. D.. and sec. 5. T. 20 X., R. 9 E. The property Avas first Avorked bv hA'draulicking, but later a connected-bucket dredge Avith

3 Averill, C. op. cit., p. 2S

28

PI.AfF.R MINIXC I OK (loi.l) (ArJFOUNIA [Bull. 135

Fio. 93. Ruby mine, underground slusher hoist. Photo by courtesy of L. L. Ifiiela- donk; reprinted from California Journal of Minea and Geology, January 19 i2, p.

Sec. IV]

Mines Uy Counties

82 buckets of fi-cu.t't. (ai)acity whs instfilled in a pond in one of tlie hydraulic juts. Overburden was stripjjcd to a dei)th of 40 feet with cater])illar tractors and i-arryalls. A few additional details about tliis operation are contained in the California .Journal of Mines and CJeolofiy for January 1942.'*

William Richtcr d Sons, Route 2, Box 400, Oroville, operated a dra<;line dred<>e ecpiipped with a l]-cu.yd. bucket on propei-ty owned bv the Pacific (las & Electric Comjauy on the Yuba River in sees. Ki, 17, T. 19 N., K. 9 E., M. D., in 1941 and 1942. Tn 1!)41 operations from June 1 to December '.U yielded 140.'5 oinices of old and 179 ounces of silver from 280,000 cubic yards of <rravel. Tn 1942 operations from Jajiuary 1 to April 80 yielded 248 ounces of jjold and 29 ounces of silver from 58,000 cubic yards of iiravel.

Ruby mine has been operated durinjr recent years by C. J. Best, 800 Davis Street, San Leandro. In 1948 operations were on a main- tenance basis only because of Limitation Order L-208 of the AVar l*ro- duction Board. The yield from 500 cubic yards of jiravel was 828 ounces of <rold and 12 ounces of silver. Becan.se of the newl\- developed methods of drift mining- used at this mine, a description of the opera- tions in 1941 is reprinted below from the California Joui'ual of Miius and Geologry for January 1942:"'

Averill, C. V., op. cit., pp. 3.5-37. Averill, C. v., op. cit., pp. 38-42.

Fig. 94. Ruby mine, timbering-. Slusher scraper at left. Photo hy conrtt si L. L. Huelsdonk; reprinted from Calijornia Jonrnul ot Mines (ind (leohiau. Jinin 131,2, p. il.

Placer Mixing For Gold In California

Bull. 335

tea;

?5

Sec. IV] MINES BY COUNTIES 291

llw Ruby ininc was beiiiji- opcrati'tl in 11)41 by C \j. l>est, Catorpillai- Tractor Company. San Leanclro, with L. L. Iluelsdoiik, (Joodyears Bar, in charge. InchuUiig a lease on the lott property, there arc 1,100 acres, of which 800 are patented, in sees. 10, 11,14, 1.1, t. 1!) X., K. 10 E., M. D. The mine is reached by If) miles of road from Downieviile, mostly steep monntain road, dirt snrface.

The lald j\Iountain E.xtension cliannel, one of the oldest Tertiary channels, branches from the Bald Monntain channel at a point nortli of Forest. Bald Monntain channel is the same as the i\nby and City- of-Six channels. The last two named are simply continnations of the Bald Monntain chaiuiel to the north. The Bald lonntain Extension channel was workeil in the Knby mine in the nineties from an adit level driven from the side of the monntain on which the town of Forest is located. Present work is on the opposite side of the monntain. An old adit level (portal elevation 4,707 feet) was ntilized for a distance of 1,800 feet. Work beyond that l)oint is new. The adit is in the Tightner formation for 3,320 feet, then in serpentine for 520 feet, then in gabl)ro and schist for 610 feet, then pas.ses into a second belt of serpentine. A point in the adit is 1,850 feet sonth of the common corner of sees. 10, 11, 14, 15, T. 19 X., K. 10 E. The contact of the second belt of serpen- tine and the gabbro-.schist is 200 feet east of the point in the adit described. The adit then continues in a general southeasterly direction to a point where a raise was put up to the intervolcanic channel. Dis- tance from the portal to this raise is 5,850 feet and the raise is 109 feet high. From the top of the raise 400 feet of drifting was done in a south- erly direction on the channel and 4,000 feet in north and northeasterly directions on the channel. From this point the channel winds consider- ably, and 700 feet more of driving will be needed to connect with the Larry shaft, of which the collar elevation is 5,163 feet and the bottom elevation is 4,954 feet. Several thousand feet of additional exploratory work have been driven on the channel, and a connection for air, involv- ing 3,000 feet of work, has been made to the Golden Bear shaft.

The intervolcanic channel that is being worked is 200 feet lower than the Bald Mountain Extension channel and cut off the Bald Mountain Extension channel. Apinirently much of the gold in the intervoleanic channel was derived from the older ehannel. The intervolcanic channel varies from (JO feet to 160 feet in width and is breasted to a height of 6 to 8 feet. Channels are capped by as much as 900 feet of lava, which is mostly andesite, but basalt is found on top of the andesite in i)laces. Large bouldei-s are stored underground. Tlie finer gravel is moved by slusher scrapers to raise-chutes and hauled in trains by storage battery locomotives to the washing plant at the portal (tf the main ailit level. Timbering comprises .stulls and caps specially designed with a mortise and tenon and handled by one man.

In the sunnner of 1941, the crew comprised 18 men, and 80 to 100 tons of gravel were treated per day, but when the crew was 43 men, 200 tons were treated per day and a maximum of 250 tons was reached. The reason for the small crew in 1941 was that many men had left to engage in defense activities Gravel passes from storage bin over Hun- garian riffles of alloy steel 50 inches wide by inches deep ; tlien to a vibrating screen, which is a double screen. The upper screen is of 2-inch square openings, and rods are half an inch in diameter. The screen which is below is four-mesli of Xo. 12 wire. T'ndersize goes to a six-unit Huels-

202 l'LA( i:i MINING FOR GOLD IX CALIFORNIA [. 135

(loiik talc 20 feet Ion;: l)y 7 feet wide. The washing plant will treat ')()() tons of TJivcJ piT 24 lionrs. The screen mentioned above is vibrated by an eccentric and 2()-lii). motor with a .']-inch stroke at the rate of 200 vibrations per minnte. Tndersize goes to the Iluelsdonk table mentioned above, which is vibrated with a -inch to 1-ineh stroke at a rate of 200 vibi-ations per minute. The end of the table farthest from the vibrating screen is set three-(piarters of an inch lower than the end near the screen. Uecovcry amonnting to 10 to 2X) percent of the total is made on this table as fine gohl. The remainder is made on the first riffle and the screen abont (vjnaily dividctl. Steel bars are placed across the screen to hold it down and these have a tendency to act as riffles. Below the screen additional i-iffles ai-c provided in the sluice tliat carries away the oversize, but little gold is recovered from these. Nuggets as big as 52.33 ounces valued at $1,758 have been recovered. C. L. Best is saving all nuggets al)ove $100 in value for exhibit purposes and in 1941 had a collection of 123 that had been recovered since 1937. Gold is 940 to 950 in fineness, lost of the tailing is stacked on the property by means of a belt conveyor.

The second .serpentine belt mentioned above is 490 feet wide, then the woi-kings pass into the Blue Canj'on slate, which is the bedrock of the channel being worked. On the contact of the second serpentine belt and the IJlue Canyon formation i,s a fault called the Independence, on which is a (i-foot (juartz vein. Another quartz vein 4 feet in widtli was cut 110 feet farther ahead in the adit in the Blue Canyon formation. A thii'd vein known as the Wolf vein strikes north and dips 65° W. It is (i inches to 12 feet in width. This vein was worked in the years 1!>35, 193(), and 1937 to a depth of 200 feet below the main adit level. Drifts were run north on the 200-foot level for 600 feet and the ore was stoped through to the main adit level. This work on the quartz vein had been discontinued and the workings are now full of water. Ore was treated in a stamp mill of 30 tons daily capacity, and treatment was amalgamation on plates followed by tables and flotation. The quartz averaged $5.80 |H'r ton in the mill but additional gold was recovered as high-grade. This vein is in the Tightner fornuition and was found at a distance of 2,120 feet from the portal of the main adit.

Cam)) facilities ai'c provided for a crew of 40 men, and the property is well e(|uii)i)e(l with r('i)air sh()j)s, drill sharpeners, air compressors, and other modern machinery. Electric power is supplied by Pacific Gas and Electric Comi)any.

Tennessee Mausmon drift mine was worked throughout 1942 by C. S. I*oor. The yield fnmi 1,200 cubic yards of gravel was 142 ounces of gold and l(i ounces of silver. In 1943 ojierations from January 1 to Xovember 1 yielded 74 ounces of gold and 8 oiuices of silver from 680 cubic yai'ds of gravel.

Sec. IV] MINES BY COUNTIES 203

Siskiyou County

Beaver Dvechjing Company, 615 F Street, Marysville, vorked a dragline dredge with a 5-eu.yd. bucket on Indian Creek 6 miles west ol" Fort Jones from April to December ;?!, 1!14].

C. & E. Drcdiiinn ronijHinif. 1002 Pacific Building, Portland, Ore- gon, operated a dragline dredge using a 2-cu.yd. bucket on Mc Adams and Cherry Creeks in the Deadwood district from May 9 to December 31, 1941.

Cal Oro Dredging Companjf, 681 Market Street, San Francisco, operated a connected-bucket dredge on the Lange property in the Green- horn district from January 28 to September 22, 1940.

Etna Gold Dredging Companxi, 1730 Franklin Street, Oakland, operated a connected-bucket dredge with 80 buckets of 3-cu.ft. capacity on Wildcat Creek 2 miles north of Callahan in 1940. The yield from 800,000 cubic j'-ards of gravel was 4299 ounces of gold and 642. ounces of silver. The operation was continued until October 1941.

Farnsworth mine in the Liberty district was operated by the hydraulic method by E. A. McBroom from March 1 to May 10, 1943. The yield from 500 cubic yards of gravel was 22 ounces of gold and 2 ounces of silver. See Salmon River Mining Company also.

The Gallia Placer Mining Company operated the Gallia mine on the North Fork of the Salmon River near Sawyers Bar during the 1932 season. The gravel was 30 to 35 feet thick and contained some large boulders. Water was brought to the mine under a 265-foot head through a 2000-foot line of 36- to 15-inch pipe. Enough grade was riot available for the disposal of tailings, and the gravel as mined contained too many boulders for the successful operation of a hydraulic elevator. The gravel was cut and swept to a Ruble elevator by a giant with a 3i- or 4-inch nozzle. It was then put through the elevator by another giant with a 4-inch nozzle. The Ruble was 4 feet wide and elevated the over- size 25 feet. The Grizzly consisted of 90-pound rails 2h inches apart set lengthwise on 10- by 10-inch stringers. The undersize from the grizzly went through a 24-inch sluice with riffles consisting of angle iron and rails placed crosswise in the boxes.

The sluice discharged into a hydraulic elevator with a 20-inch intake. A 4-inch nozzle was used in the high-pressure jet ; the material' was elevated 30 feet. The elevator discharged into a second sluice.

The capacity of the plant Avas limited by the quantity of material that could be run over the Ruble elevator. The cutting and driving giant was used for a few hours and then shut off until the accumulated material could be handled in the Ruble. The giant at the Ruble oper- ated continuously. About a week with the full crew Avas required to move the Ruble ; it had to be moved every 3 weeks, as the dump room behind it was exhausted.

Boulders too large to go up the Ruble were moved back by a derrick. Large boulders uncovered in cutting were dragged from the pit by means of a donkey engine. Water was used not only for the giants in the pit and the jet of the hydraulic elevator but also for operating the derrick and running a dynamo for operating a sawmill and an air compressor.

Gardner, E. D., and Johnson, C. H., Placer mining in the western United States, Part II, Hydraulicking, etc. : U.S. Bur. Mines Inf. Circ. 67S7, 1934.

2!)4 im-A(i:k iinint. i-ok cof.d in cAuroHNiA [Bull. 135

The workiiiir ci-ow consisted of two men in tlio jiit and oiio man on tlio ditcli liiu on cadi of two 12-lioiir shifts. Alth(u<rli to (50 fnhi<' yards por hour could ho cut and swept to the IJuhle hy the cutting-iant. the avera-rc capacity, includinjr the time for moving' the was 200 euhic- yards per (hiy. The lal)or eost. assuminr per man-shift, would he 11 cents per cubic yard. The eost of supplies would he about 2 cents and supervision 4 cents, makin<:- the opei-atini' cost 17 cents.

I[nf>i)ii f'diiii) Drahfliifi Cain paini. Happy Camp, ojx'i-ated a dra'- liue dredte on the Allen property from May 1 to .May :{1. 11)40. The dredfre was then moved to ])roi>erty owned i)y (Irani Smith and was ojierated there from September 1 to November .'0.

Horfon diilrh Mint was described by (Jardnor and -lohnson- as follows:

J. (). FcUroom operated the llortou (luleh i)laeers on the Soutli Fork of the Salmon River near CVeilville. The 1032 sea.son extended from January 1 to April 11. The <rravel was fairly ti<rht. The jrrade of bedrock was 1 inch to tlie foot. One <iiant with a o-inch nozzle, work- iiiff under a G.l-foot head, was used for both cuttinjr and sweepin<r the jrravel into the .sluice l)oxes. About 30 inches additional by-wash water was u.sed for movinji' the 'i-avel throujrh the sluice which consisted of three 12-f()ot boxes 24 inches wide. The riffles were hard boulders liaiid- shajH'd to make a pavement 7 to 10 inches thick. A)i undercurrent was u.sed for 1 month and then discarded ; about 1 ounce of pold was cleaned up from the undercurrent durinr the month's run. All larjre boulders were blasted. An averajje of 80 cubic yards per day was washed durinr the 1932 season. Two men were employed. At $3.50 per shift the labor eo.st would be f) cents; supplies would amomit to about 2 cents per cubic yard, makiiifr a total of 11 cents.

Jonhert mine in the Liberty district was worked by lessees, H. J. Dickinson, Stanley Czerwinski, and others of Sawyers Bar in 1940 and 1941. Hydraulic operations in 1940 yielded 354 ounces of f?old and 55 ounces of silver. In 1941 the yield from 27,900 cubic yards of gravel was 385 ounces of jrold and 58 ounces of silver.

Larsen Bros, and Ilarnis Bros., Route 4, Box 2220, Sacramento, operated dragline dredges on the Klamath River and on Horse Creek during 1940 and 1941. In 1943, 114 ounces of gold and 18 ounces of silver were recovered from concentrates accumulated at the Moccasin dredge before it was clased because of War Production Board Limitation Order L-208. The following description of operations in 1940 are reprinted from the California Journal of ]\Iines and (Jeology for April 1941:3

Scandia mine, in sees. 7, 8, 9, 15, T. 4(5 X., R. 10 W., M. I)., on Horse Creek near the Klamath River, was being operated in 1940 by Lar.sen Bros, aiid Harms Bros., Route 4, I>ox 2220, Sacramento. Emmet Miles, Hor.se Creek, Siskiyou ('ounty, was in charge at the mine. The property is reached by means of 2 miles of dirt road turning from the graveled state highway along the Klamath River.

a Op. clt.

Averin, C. V., DragUne dredglnj? in Siskiyou County : California Jour. Mines and Geology, vol. 37, pp. 328-331, 1941.

Sec. IV]

Mixes Hy Couxties

29."

reilge at Scandia mine.

Low bar.s of Iloi'se Creek for a total length along the creek of 6 miles Avere being dredged. The width was abont 1,000 feet in the lower part of the tract but less al)ove. Depth of gravel was 12 feet to 18 feet and practically all the gold was in the lowest 2 feet. From a tract of 100 acres about 2,000,000 cubic yards had already been dredged in the fall of 1940.

The washing plant is of Bodinson make and is similar in all respects to the ones described in the chapter on dragline dredging (ante).

It is of 3,600 bank-yards capacity per 24 hours and is built to serve a 3-cu.yd. dragline excavator. The bucket in use is a 2j-yard Esco. The trommel is punched with f-inch to f-inch holes, and nndersize goes to standard-dredge-type Hungarian riffles. Murphy 6-cylinder diesel engines rated at 160 hp. each supply the power on both the excavator and the washing plant.

The following figures on cost of equipment and cost of operation were furnished by Emmet Miles: 95 Northwest dragline with 60-foot boom, $58,000 ; washing plant, $40,000 ; D7 tractor with bulldozer, $7,000 ; D8 tractor with carryall, $10,000; truck, welder, pickup, $1,900; miscel- laneous lighting plants and pumps, $1,000; air compressor, $200; spare generator for washing plant, $900. The last item mentioned furnishes power to an electric motor on the upper end of the belt stacker. The total crcAV comprises 14 men.

Gravel actually washed on boat cost 5 to 6 cents per cubic j'ard to handle. Cost of removing and leveling overburden was 7 cents per cubic yard. No depreciation was included in these costs. To cover the cost of mining, stripping overburden and leveling, including depreciation but excluding profit, it was necessary for the gravel to run 10 cents per cubic yard.

Restoration of the land in order to make it available for farming appears to be an accomplished fact at this mine. A tract of 100 acres is being so restored, nd 60 acres were to be planted to new crops, alfalfa, rye, and sweet clover in the fall of 1940. Some of the fields were already green with the new crops in October, 1940.

Plackr Mining For Gold In California

[HuU.l.'Jo

The laiul alon": the creek averajres 1,000 feet in widtli. It carries an ovcrhiinleii of soil o to 6 feet in deptli. For dredfrinpr, it is divided into strips roujrhly MOO feet in width. P"'roni tlie first strip the soil over- burden is removed to wasteland aloiifr the outside of the tract. This i.s done with a D8 Caterpillar tractor and a carryall of 12 cubic yards capacity. At times a second outfit of 16 cid)ic yards capacity has been in use. After the soil has been removed from the MOO-foot strip, the jrravel beneath is dredged with tlie drajrline to a depth of 12 to.lH feet. The belt-stacker on the dredie leaves the gravel behind in conical piles about 20 feet hij;h. Next a Caterjiillar tractoi- with bulldozci- attachment levels these inles, and the runninjr back and foi-th of the heavy machine packs tlie jiravel considerably. Then the soil of the second :iOO-foot strip is removed by the carryalls and placed on the leveled <rravel of tlie first strip, and is spread out and <iraded so tliat the land is ready for farminjr. The process is continued to the last strip, where the <ri'avel is spread in the form of a dike to hold tlie stream in a i)rei>ared channel. l*i-eviously the stream i-an near the center of the tract and {Jfave trouble from floodinjr and washin the land. Hence, the operators believe that the land is left in better condition for farming- than it was orifrinally.

Efforts have been made in the ])ast to level the pravcl fi-om a ;.'e and to throw out the fines directly from the dredge on top of the f?ravel. Disturbinjr of the {iravel by the dredjre results in an increase of voids between the various boulders and cobbles, and the fines jro into these voids to a jireat extent. Even if soil is left on top. it may jii-adnally sink to fill the voids, leaviufr iiravel and boulders exposed on the surface. The present method overcomes the difficulty in two ways : the lieavy machines pack the jrravel. and the five to six feet of soil put on top <rives a wide marrin of safety.

Unfortunatt'jx- this method can not be api)lied to all drcdjrinjr-land. First, the avei-aj:e tract does not contain such a thick layer of jiood soil. Second, the method is expensive, and the averajze tract does not contain enoujih jrold to jiav for it. The operators fi<rure that the extra cost of restorinr the land was .H<2(),0()0 for a tract that is worth less than $10,000 as a farm. As an example of the expense in\dlve(l, consider the fact that one ti-actor woi-tli about $H,0()() had alreadv been worn out in rou":ld\-

Fii;. 'j7. Dragline ilr.ilm- at Micca.sin min<-.

Sec. IV] WINKS BY COUNTIES 297

a year and a half, and in the fall of 1940 a second was well on the way to being worn out.

However, the land along Horse Creek contained enough gold to pay for the restoration and a profit besides. The original restored tract was used to induce the owner of an adjoining tract to allow his land to be worked by the same method, so the Avhole operation is profitable.

Moccasin mine, in sec. 14, T. 4(i X., K. 10 W., M.D., was also operated by Larsen Bros, and Harms Bros., Route 4, Box 2220, Sacramento, in 1*940. The property is on the Klamath Hiver about li miles up the river from Horse Creek. It is reached from the bridge at Horse Creek by means of a road up the nortii bank of the river. A river bar about 2,000 feet wide cari-ying gravel to a depth of 18 feet to 35 feet was being dredged. Total depth in some places including 10 feet of fine over- burden was 45 feet.

The Moccasin outfit includes the largest dragline excavator used for dredging in northern California. The only larger dragline used for any purpo.se is the one that excavates gravel from the Sacramento River at Redding for aggregate to build Shasta Dam. The 5-yard :\lonighan at Moccasin mine walks around much as a man walks and is equipped with a large foot on each side for that purpose instead of the Caterpillar treads commonly used on smaller draglines. It has a 100-foot boom and is capable of digging to a depth of,45 feet. The bucket in use is a 4i-cu.yd. heavy-duty Esco.

The washing plant is of Bodinson make and has a capacity of 6,000 cubic yards per 24 hours. Tlie trommel is 47 feet by 72 inches and the largest holes are three-quarters of an inch. All (abrasion resistant) steel used on the first section of the trommel had given 7i months of service in the fall of ]!I4(). The pumi) is a 14-iiu-h United Iron Works pump driven by lOO-lip. (Jeiieral Electric motor. The 85-foot stacker carries a 42-inch belt. The barge is 40 feet Avide by 64 feet long by 54 inches deep. Power is furnished by a :{00-hp. Fairbanks ]\Iorse diesel engine on each machine, the dragline and the washing plant. The engine on the washing plant di-ives a 200-kva. Fairbanks Morse alternator, 480 volts. ]?oil-boxes similar to those used by Lincoln Gold Dredging Company in Ti'inity County are used under the trommel. A manifold supplies jets with Avater under pressure in the various compartments beneath the trommel and thus the sands are kept in agitation.

The overburden, 10 feet in depth, is removed aiul piled to one side by means of a D8 Caterpillar tractor and a 12-cu.y(l. carryall. No attempt is made at resoiling as at the Moccasin mine. The river was to be turned into a channel prepared for it on the north side of the tract during the winter, 1940-41, so that the present channel of the Klamath River could be mined. Near the river the gravel is. free of overburden and is 18 feet in depth. The width of the pond being carried in 1940 was 500 feet.

Costs of principal items of equipment set up on the job were furnished bv R. II. Wallace, superintendent, as follows: Monighan, $75,000 ; washing plant, $70,000 ; D8 tractor and carryall, $16,000. The total cost of operating the equipment per cubic yard of gravel was stated to be 9 cents.

Lincoln Gold Dredging Company, Lincoln, operated a dragline dredge equippedAvith excavator having a Ij-cu.yd. bucket on the Calkins

208 i'LA( i:k mimxc (Kir.D cAr.iioHMA l)iill. Ill')

property 1 mile rjist of VrcUa from .July 7 to Dci-cnibcr 2, 1!>41. Tlio yield fi'oin !K},742 ciiltie yards of jrravel was .").")(; ounees of jrold and 78 oiniees of silver. In addition. E. A. KinUle recovered a small (piaiitity of jrold hy nsin a dry-land plant. The same two operators also worked the Hose projierty. In 1!>42 the company operated a drajriine dred.!e on several properties as follows: from j)ropei'ty owned by the City of Vreka the yield was .'{()4 ounces of <r(ld and 44 ounces of silver from 4:{.()2!) cubic yards of jii'avel ; fi-oiri (Jeneral Dredjjre property the yield was 1844 (Unices of 'old and 2iV.i ounces of silver fi-om 272,42."i cubic yards of pravel ; and from the \unes projiei'ty the yield was 2.')I> ounces of <rold and .'{7 ounces of silver fi-om .M.12H cubic yai-ds of gravel. All of these pi-operties are in the (Ji-eenhorn district.

MtQii(cn and Downiiic,, 12") Dexter Sti-eet, Vi'cka, ojx'ratcd a di-ar- line dreda' on the Xeville and Silva ])i-o|KM-lies in the Klamath River district durin-r U41.

Midhind Comjxtiui, Inc., 1112 Pearl Street. Alameda, operated a drafrline dredjic which had a li-cu. yd. l)ucket on the Xorth Fork of the Salmon Hiver in Libei-ty disti-iet throuliout lf)41. The yield from ()()() cubic yards of <rravel was l!l.")() ounces of <rold and 284 ounces f)f silver.

Norfhcrn Drrdgiinj Coinj)anij, Kearny Street, San Francisco, ojierated a drajiline dred:e on tlie Allen the Collins properties in tiie Klamath River di.strict from January to 1041, when the company was dissolved. A drajriine excavator with a 2-cn.y(l. bucket wa.s used.

Okoro Mi)ic.<t, Inc. of Callalian operated a drajrline dredjje inter- mittently from January to June 1040 and washed 4;3,()0() cubic yards of p:ravel, from Avliich 218 ounces of <ioId and 31 ounces of silver were recovereil. In 1041 operations coiulucted from July 11 to December 31 with a di-a;:line dredjrc efpiipped with a. 22-cu.yd. bucket yielded 771 ounces of <rol(l and 101 ounces of silver from 24r),000 cubic yards of fri-avel. In 1042 ojierations with tlie drajrline di-ede on the Ilayden property during: the month of January yielded 103 ounces of j'old and 10 ounces of silver from 60,000 cubic >ards of irravel.

TriuH\i Drcdgiiu/ Coinixnuf, liox 212, Oroville, ojierated a draj?- line dredjre which had a 1 '-cu.vd. bucket on Scott River during 1040 and until May 31, 1041.

I). Sdcchi, K. L. )il>(r(i, and F. Kiddi, of Areata, operated a drajrline dredjre usinr a H-cu.yd. bucket at forks of Salmon inter- mittently durin*.'- 1040. They recovered 'Mi7) ounces of gold and 53 ounces of silver,

Salmon Ifii'cr Gold 1)nd<i'n\<i ('ninjxiin/, 310 Kearny Street, San Francisco, operated" a drajiline dredfre. usiujx a 3-cu.yd. bucket on several properties in the Salmon River district during: 1041.

Salmon River Mining Companxf property was described by (lardner and .Johnson as follows: The Farnsworth brothers operated the mine of the Salmon River Mininr Com])any on the South Fork of the Salmon River near Cecil villc dui-in<r tlie 1032 season. The "travel consisted of G feet of pay dirt overlain with 11 feet of overburden. The grade of the bedrock was three-fourths of an inch to tlie foot. Water under a 22;)-

♦Op. cit.

Sec. IV'] MINKS 15V rorxTiics 299

foot head was l)r()ii<zlit lo the mine tlii-ouji:li a :.}-inile ditcli and 1 mile of pipe line. The diameter of the fii-st :50()() feet of the pipe line was 22 inches. This was reduced to IS and then to 1") inches at the pit. The branch line on the floor of the ])it to the different riants was of 11-inch pipe. Foui- jiiants with (J-inch noz/les weie set H|) in the pit, but only two were used at a time. A fifth <riant with a ")-incli nozzle was set up at the lower end of the sluice. I'sually one <;iant cut the bank and one of the same size swept the {Travel to tlie head of the sluice. The river ran alonjiside of the {jravel bein>' washed, and the sluice box emptied into it. The river water carried the sand and fine jiravel downstream; coarse nuiterial, however, piled up in the stream. The dump giant was used 1-2 to 2 lioui-s dui-ing the working shift to stack the coarse material at the end of the box. At the end of the washing shift this giant was set with an automatic control so that water played on the boulders until the next moi-ning. A windrow of boulders 80 feet high along the opposite bank of the rivei- had been made by the giant. The largest boulders were washed to tlie top of the pile. The stream played in a vertical arc; it was depressed slowly and went up faster. About 1 minute was con- sumed in each cycle. The giant was overbalanced so that the stream was elevated Avhen free. It was pulled downward by means of a 2-inch hydraulic cylinder fed through a hose from the pipe line. At the end of the stroke a trip turned a valve which shut off the water to the cylinder; at the top of the upward swing anothei- trip opened the water valve. Each morning the river bed at the end of the sluice was free of boulders.

The sluice boxes were 36 inches wide by 30 inches liigh and were set on a grade of 7 inches to each 12-foot box. One setting of the sluice-way was sufficient for a season's work. The head boxes were protected by parallel roAvs of 6-inch poles placed horizontally on either side of the box. The i)oles were laid on an earth fill, the surface of Avhich slanted upward at an angle of 25° from the edge of the boxes. At the end of the season the poles Avere removed and the underlying gravel Avas Avashed into the boxes. The riffles in the sluice consisted of rock paving. Diorite boulders with one flat side Avere selectee from the Avashed gravel in the pit. These stones Avere dressed by hand to make a rigid paA-ing Avitli a fairly smooth upper surface. Formerly Avooden blocks were used, but they had to be replaced every 60 to 70 days. The sluice was cleaned up at the end of the Avashing season. An undercurrent was used at the loAver end of the sluiccAvay. The screen consisted of f-inch round steel rods 15 inches long, placed inch apart lengthAvise Avith the sluice. The undercurrent table AA-as 5 feet Avide and 11 feet long; wooden Hungarian riffles Avere used. Quicksilver Avas used in the sluice box ; some reached the undercurrent Avhere it Avas caught in the riffles.

Boulders up to 18 inches in diameter Avere put through the sluice. A hand derrick Avith a 25-foot mast and tAvo 30-foot booms Avas .set at the head of the sluice to remoA'e any oversize boulders that Avere Avashed to this point. A derrick hoist AA-as used for dragging stumps and large boulders from the main part of the pit. The hoist pulled over a 25-foot mast guyed Avith 4 lines ; apparently, hoAvever, 5 lines should have been used. The cable (11 inches in diameter) was pulled out by hand; the range Avas 400 feet from the hoist set-up. The hoist Avas double-geared and was run by an undershot Avater Avheel driven by a 1 J-inch nozzle. A stream from a 1-inch nozzle Avas used on top of the water Avheel for

300 PLACER MINING FOR OOLD IN CALIFORNIA [Bull. 133

braking!:. No exjilosivcs were used in the mine. The overburden was washed from the top of the fjravel and i-un directly into the river. This work was done dnrin<r lo\v-\vatei- periods when enough water for only one giant was available.

Lumber cost $30 i)er M. An averajre of 223 cubic yards was worked per day during the 11)32 season. The opcratinjr cost was 7 cents per cubic yard with lal)or at H cents.

Shasta Drcdgitu/ Coiiijxniy (Thompson dredjre), 737 North Central Avenue, Stockton, operated a dradine dred<re on Hrasswire Gulch

1 mile southwest of Iloridirook from May 12 to August l(i, lf)41, after movinj: the equijiment from the .lemiy liind district in Calaveras County. The dragline excavator was equipped with a 2J-cu.yd. bucket.

Surveyor's Mistake mine on Vesa Creek in the Klamath Kiver dis- trict was operated by Henry Beauman of Klamath River Post Office, during 1941. He used a non-floating washing plant to which gravel was delivered by mechanical means.

Von der Hellen and Webber, Box 217, Yreka, operated a dragline dredge using a 2-cu.yd. bucket on Humbug Creek throughout 1940. The operation was continued from January 1 to October 1, 1941.

yVilliam von der Hellen Mining Company, Box 1026, Medford, Oregon, operated a dragline dredge with excavator equipped with a 2-cu.yd. bucket on the Klamath River throughout 1940. In 1941 the operation was continued, and tlie yield from 773,700 cubic yards of gravel was 6113 ounces of gold and 928 ounces of silver. The operation was continued at McConnell Bar from January 1 to September 27, 1942, with a 3-cu.yd. bucket and the yield from 596,800 cubic yards of gravel was 3594 ounces of gold and 554 ounces of silver.

Yreka Gold Dredging Company, 351 California Street, San Fran- cisco, completed its operation 2 miles north of Yreka in 1940 and then moved its dredge to Seiad Valley, where operations were resumed on September 14. 1940. The dredge was equipped with 67 buckets of 6-cu.ft. capacity. The following description is repainted from the Cali- fornia Journal of Mines and Geology'' for April 1938:

Yreka (iold Dredging Company built a new dredge in 1937 to work in sec. 14, T. 45 N., R. 7 AV., M. D., and adjoining sections along

2 miles of Yreka Creek just north of Yreka. Ethredge Walker is presi- dent and Albert Schubach is secretary, Balfour Building, San Fran- cisco. Eric Peterson is dredge-master at Yreka. The dredge was built by \yalter AV. Johnson Company. Balfour Building, San Francisco, and the following details are furnished through the courtesy of that company.

The hull is approximately 82 by 42 by 7 feet, and is made of 19 pontoons about 20 by 10 by 7 feet, weighing 6 tons to 7 tons each. Exposed walls are made of V'j-inch steel and inside walls adjacent to othei- pontoons are of ,-',;-inch steel. The pontoons and all structural parts, the digging and stacking ladders, frame for revolving .screen, distributors, and 10-ton spud are of electric- welded construction, which has proved very satisfactory.

The bucket-line carries buckets of 6-cu.ft. capacity each, to dig to a depth of 25 feet. Buckets are of the new rivetless-lip, bowl-shaped

Avcrill. C. v., Cold dredging in Shasta. Siskiyou, and Trinity Counties: Califor- nia Jour. Mines and (Jeology, vol. 34, pp. 123-125, 1938.

Sec. IV] MINES BY COUNTIES 301

clesign, and are made of mani!:anese steel by American Manganese Steel Company, Oakland. Lower tumbler is made of manganese steel and is round ; upper tumbler is of high-carbon steel, six-sided, and cast integral with shaft. The hopper-chute is lined with manganese steel bars. A. special feature of this is a removable back plate for dis- charging boulders too large for the revolving screen. The boulders are dumped, without stopping the bucket-line, on a fork made of heavy bars. These are swung by a heavy shaft operated by a compressed-air cylinder to dump the boulder into a steel-lined chute which discharges into the pond. Dumping is regulated by a gate in the chute, so that the boulder can be placed in some part of the pond where it will be out of the way.

The revolving screen is 34 feet long by 6 feet in diameter, and is lined with manganese steel plates. Perforations are f-inch to -inch and f-inch to f-ineh in the sections of screen except the last, which has f- by -inch slots for recovery of nuggets. Several feet at each end of the screen are not perforated. Undersize from the screen is treated on 1600 square feet of riffle-tables. Riffles are of angle-iron, l-j% inches by Ijjr inches spaced at 1 inch ; also of wood, some shod with steel, some with rubber. They are IfV inches deep spaced at 1 inch. Oversize from the screen is stacked by a stacker 90 feet long carrying a 36-inch Amer- ican Rubber Company rib-stacker belt.

Water is pumped from the pond by Byron Jackson pumps of 82 percent efficiency. The 10-inch high-pressure pump furnishes 3200 gallons per minute at 65 feet head to the revolving screen. The 8-inch low-pressure pump furnishes 1800 gpm. to the riffle-tables. A 4-inch pump is provided for cleanups, washing decks, and fire-protection.

The winch is a combination ladder-hoist, swing-line and spud-line winch controlled entirely by compressed air. This method of control adds to the efficiency of the dredge. A two-speed, specially designed motor delivers 55 hp. at 1200 rpm. or 35 hp. at 600 rpm. At the higher speed, it provides ample power for rai.sing the digging-ladder, raising the spud, and swinging the dredge when stepping ahead. The low speed is used for swinging during regular digging.

Other electric motors are as follows : 100-hp. variable-speed on the bucket-line, 60-hp. on the high-pressure pump, 15-hp. on the low-pressure pump, 40-hp. with reduction gearing on the revolving screen, 25-hp. with reduction gearing on the stacker, and 3-hp. on the fire-pump. Power is transmitted by the bucket-line and winch motors to the driven pulleys with multiple V-belt drives.

Power is taken on the dredge at 2400 volts and is stepped down by three 100-kva. transformers to 440 volts. A 5-kva. transformer is provided for lights.

The dredge is operated 24 hours per day by one dredge-master, three winchmen, three oilers, two shore-men, one tractor driver, and one cleanup man. The direct operating cost is 4.3 cents per cubic yard to which should be added cent per yard for management and ship- ment of bullion. No depreciation, no land-cost and no royalty are included. The capacity at Yreka is 140,000 cubic yards to 150,000 cubic yards per month. The same dredge would handle 210,000 cubic yards in easier ground. It cost approximately $160,000 including some mis- cellaneous pumping equipment for pumping muddy water out of the

pla(i:r AfiMxr, for ooi.d ix rAUFORxiA (Bull. 13.')

Fig. ;tS. Steel luill .Ir. .Iui -r i;,,ll li|.,l-;ii,

<-(lli/„r,ii,t .Jo„,.,ul ui Mi.n.s ,i„,t (...,l..,ni. .1/'

f-.

Sec. IV] MINES RY COUNTIES 303

poiul, but not iiu'liidiufi' tlio ilf)-!!)). CntcrjiJliir tractor with diesel cMifine and bulldozer.

Yuha Consolidated Gold Fields (Siskiyou Unit), 351 California Street, San Francisco, was the leadin< gohl producer in Siskiyou County in 1940. The company operated a Yuba type connected-bucket dredge with 72 buckets of !)-cu.ft. capacity near Callahan. The operation was continued throughout 1941.

The following description of the dredge is reprinted from the Cali- fornia Journal of Mines and (ieology " foi- April, 1938:

Yuba Consolidated (lold Fields built a new dredge near Callahan, Siskiyou County, in 1936, in sec. 8, T. 40 N., R. 8 W., M.D. P'rom a point near the confluence of Wildcat Creek and Scott River, it will work for sev'eral miles up the river. F. C. Van Deinse, 351 California Street, San Francisco, is vice-president and general manager. H. C. Perring is field-superintendent.

The dredge is No. 116 of Yuba Manufacturing Company, and is built on a steel hull not of the pontoon type, 122 feet 8 inches by 56 feet by 10 feet. It will now dig to a depth of 35 feet below water line, but is designed so that extensions can be put on both the hull and the digging- ladder ; and it will then dig to a depth of 50 feet or 60 feet. To cope with very difficult digging, this dredge was equipped with machinery of sizes ordinarily used on dredges with 18-cu.ft. buckets, while its buckets are of 9-cu.ft. size. Concentric ladder suspension is used, that is the ladder and the bucket-chain turn on the same axis.

Gravel is screened in a trommel 8 feet in diameter by 48 feet long, of which 34 feet are perforated with |-inch to f -inch and f -inch to -inch holes. It turns at 7 rpm. The trommel is lined with f-inch plates of "abrasion resisting steel," a high-carbon, high-manganese steel supplied by United States Steel Corporation. It costs more per pound than ordinary steels but less per cubic yard dredged. Undersize from the trommel is treated on 3500 square feet of riffle-tables in a double-deck arrangement. They are provided with wooden riffles shod with steel. For washing, 10,000 gallons per minute of water are pumped from the pond. The total connected load is 750 hp., which includes an extra-heavy digging motor about midway in size between those customarily used in 18-cu.ft. dredges and 9-cu.ft. dredges.

The dredge is operated for 24 hours per day by a total crew of 24 men including a man in the office. The actual capacity is 210,000 cubic yards per month in ground that is hard to dig.

Averill, C. V., op. cit.

304 rLAf-KR MININO I'OU COLT) IN' CAr,II'()KNIA [RiilLlHr)

Stanislaus County

K Prrdfjinn ('oniixnni, 1002 Pacific I'.uildin'. I'ort land. Orcjoii, op<M-at('(l a (Irajrliiie di-cd'c with excavatoi- liaviii' a 1 i-cu.yd. bucket on Littlejolm Crceiv two miles iioctliwest of Knidits l-'erry inteniiitteiitly between ScpteiidxT 20 and December 17, 11)40. The same ecpiipment was ti.sed in dredfi-injr the ad.)oinin<r -lack Welsii Uancli.

Cnlifoniid Hold Dr(<hjiii<j Coin pahif. ;{')1 Califoi-nia Street. San Fi'ancisco. operated a eonnected-bncket dredre in the .Jenn>- Lind dis- triet on tlie Stanislaus side of tlie connly line diii-inj; 1!)40.

(icrmuiii, A. (!., o])erated a dra<;line dred<re nsinj? a .l-cu.yd. bneket in tlie Knijrhts Ferry district intermittently t'l-om .Inly 1.") to December 28, lf)4:i The wasliin;.'- of (iof) cubic yards of <rravel yielded 12 ounces of {joJd and 1 onnce of silver. The e(pii{)ment was desi<rne(l to be handled by one workman.

La (Irauijc Hold /iiuf CoHipniiji, IHOf) Mills linildiiifr. San Fran- cisco, oi)erated a eonnected-bncket dre(l<i:e on the Tnohnnne River in tlie La C}ran<j:edist]-ict throu<.diont l!)40and 1!)41. The dredjre was e<piipped with ()2 l)nckets of l()-c\i.ft. capacity.

Placer J'roixrtics Coiiipaiiif, liox y>'.V2, Oakdale, <)i)eiate(l a di-a<iline drede on the Stanislaus River nine miles east of Oakdale thi-onjjhout lf)40. A ()!- and a 7i-cn.yd. bucket were tried on a o-cn.yd. drajrline excavator at various times dni-in<i' the yeai'. The washin<i- plant used a shakinjr screen in l)lace of a trommel. In 1!>41 operations were continued with a ()-(Mi.yd. bucket at a point eijiht miles east of Oakdale. In 11U2 operations were continued (lni"in<r most of the year with two di-ajjfline excavatoi-s. one with a H-cu.yd. bucket and the otiiei- with a 2.',-cu.yd. bucket. Operations were continued until I)ecend)er 12, l!(4.'i.

Tuolkniiic (iold l)rrd(fin(/ Cftvporaiio)!, 1 Montromery Street, San Francisco, operated a connected-bucket dred}ie from February 22, 1!)40 until Ai)ril l."{, li)41, when the (lred<:e capsized. It was c(piipped with 100 buckets of 12-cu.ft. capacit.v. ( )p('rati()ns were cai-ricd on throughout li)43 (Ml a one-shift basis.

Vanvicl, C. F., Route 2, Oakdale, oi)erated a drajrline dredge, employ- in{r an excavator with a 1. l-cu.yd. bucket on the Anderson, Ili;rinbothani. and Kaasa pi'operty in the Knijihts Kerry disti-ict from May 1'\ until December 1:. lf)41. The yield from ()2H.400 cubic yards of <rravel was 2.1})H ounces of <rold and 17!) ounces of silvei-.

Yiiha Consolidated Oo'd Fields, :{.")1 ("alifornia Sti-eet, San Fran- cisco, started operations with a connected-bucket di-cd;.:!'. electrically driven, in the La (!ran<re district on December 1."). 1!)41.

Sec. IV] MINES BY COUNTIES 305

Trinity County

The mineral resources of Trinity County have been described in the California Journal of Mines and Geology for January, 1941. Further details about many of the placer mines mentioned below are contained in this report, as well as descriptions of lode mines and of mineral deposits other than gold. The report contains a long table of mines with references to earlier reports.

Arhuckle mine is a hydraulic mine near Weaverville that was oper- ated by Arbuekle Bros, of Weaverville during 3 months of 1940.

B. H. K. Mines, Box 325, Orland, operated a dragline dredge equipped with a l|-cu.yd. bucket on Littlejohn Creek in the "Weaverville district from July 1 to the end of 1940. The yield from 184,000 cubic yards of gravel was 789 ounces of gold and 40 ounces of silver. In 1941 operations were continued on Little Browns Creek at several properties with the following results : at the Rehberger property operations from January 1 to May 2 yielded 751 ounces of gold and 41 ounces of silver from 176,000 cubic yards of gravel ; at the M. K. Brown property opera- tions from May 3 to July 1 yielded 405 ounces of gold and 24 ounces of silver from 95,000 cubic yards of gravel ; at the Scharr property opera- tions from July 20 to September 12 yielded 349 ounces of gold and 28 ounces of silver from 81,500 cubic yards of gravel ; and at the Tye prop- erty operations from September 13 to October 22 yielded 150 ounces of gold and 10 ounces of silver from 55,000 cubic yards of gravel.

0. R. Batham, Box 325, Concord, operated a dragline dredge on the Bazet Estate property on the East Fork of Stuarts Fork from August 10, 1941 to the end of the year. The recovery from 205,550 cubic yards of gravel was 626 ounces of gold and 50 ounces of silver. Batham also carried on smaller operations at the Hook and Ladder and Nugget Bar properties.

/. P. Brennan, 1343 Butte Street, Redding, operated a dragline dredge using a f-cu.yd. bucket on Brown's Creek in the Weaverville district from July 17 to December 31, 1941.

Canyon Placers on Canyon Creek was worked by the hydraulic method by G. H. Bergin of Junction City in 1940 and 1941. More than a page of additional information about this property is contained in California Journal of Mines and Geology for January, 1941.

Carrville Gold Company, 351 California Street, San Francisco, or 807 Lonsdale Building, Duluth, Minnesota, operated its dredge on the Trinity River about 3 miles north of Trinity Center throughout 1940 and 1941. Operations were conducted through the company's agent, Yuba Consolidated Gold Fields. The connected-bucket dredge has 75 buckets of 12-cu.ft. capacity.

Cinco Mineros Company, First National Bank Building, Oroville, operated a dragline dredge using a 1-cu.yd. bucket near Hayfork throughout 1940. The operation was continued in 1941 on the Albiez, Crews, Parmenter, Ross, and Trimble properties.

1 Averlll, C. V., Mineral resources of Trinity County ; California Jour. Mines and Geology, vol. 37, pp. 8-89, 19 41.

" Averlll, C. v., op. clt., pp. 29-30.

PLACKR MININO FOR OOI.D IN CALIFORNIA [BuU. 135

Fio. 100. Goldfield Coiisolidutt d Company, hydraulic mino. /.'.;) California Journal uj Mines and Geology, January 191,1. p. o7.

Fi(5. 101. DredKe of Junction City Mining Company. Keprinted from California Journal of Mines and Geology, Jannary 193S, j)- ''7.

Sec. IV] MINES BY COUNTIES 307

Dobbin Gulch Drcdcjing Company of Redding operated a dragline dredge equipped witli a l]-('U.yd. buclet on the M. A. Brady property in the Weavorville district from June 18 to December 24, 1941. The yield from 213,800 cubic yards of gravel was 926 ounces of gold and 80 ounces of silver. In 1942 operations at the Brady property and the Sunshine mine were conducted from January 3 to October 19. At the Sunshine mine 107,300 cubic yards of gravel yielded 348 ounces of gold and 33 ounces of silver.

Golden Gravels Mining Company of Junction City operated at the Red Hill mine of Goldfield Consolidated Mines, near Junction City in

Goldfield Consolidated Mines, 1 Montgomery Street, San Francisco, operated its Red Hill hydraulic mine near Junction City in 1941 and jH-oduced a substantial quantity of gold. The mine was also operated during 1943.

Havilah Gravels, Inc. of Lewiston operated a dragline dredge which had an excavator with a 2-cu.yd. bucket on Eastman Gulch from November 23 to December 31, 1941. The yield from 7860 cubic yards of gravel was 338 ounces of gold and 48 ounces of silver. A nonfloating washing plant operated by J. W. Martin and R. W. Setzer on the same property from January 1 to August 1, 1941, recovered 163 ounces of gold and 19 ounces of silver from 20,000 cubic yards of gravel.

Interstate Mines, Inc., Box 14, Weaverville, operated a dragline dredge on the Lowden Ranch from January 4 to July 14, 1940.

Junction City Mining Company, 685 Sixth Street, San Francisco, operated a connected-bucket dredge near Junction City in 1940, 1941, and until October 28, 1942. In 1942 the yield from 2,077,000 cubic yards of gravel was 7878 ounces of gold and 735 ounces of silver. The following additional details about this dredge are reprinted from the California Journal of Mines and Geology for January 1941.

Junction City Mining Company started a modern steel bucket- ladder dredge in sec. 18 and adjoining sections, T. 33 N., R. 10 W., M. D., near Junction City, on January 10, 1936, and has been operating con- tinuously since that time. The company controls 8 miles of the river, the lower (northerly) end of the property' being in sec. 1, T. 33 N., R. 11 W. Harvey Sorensen, 685 Sixth Street, San Francisco, is president ;

C. M. Derby, Mills Tower, San Francisco, is consulting engineer; and

D. B. Wilson is superintendent at Junction City.

The hull of the dredge is new and of the late pontoon design, being no. 113 of Yuba Manufacturing Company. Transportation over moun- tain roads was one reason for adopting this design. The hull is 120 feet long by 52 feet wide by 8 feet 1 inch deep, and is made of 31 pontoons. These are designed and arranged so that the inside walls strengthen the hull at critical points. The largest pontoon weighs 24,000 pounds and the smallest 4800 pounds. Most of them weigh from 10,000 to 16,000 pounds. When assembled they form a rigid structure owing to the beam-effect of the side-walls. Some of the machinery from the old Madrona dredge was used.

3 Averill, C. V., op. cit., pp. 40-42.

308 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Tlie biK'ket-chaiii contains 7!) buckets of 9i-cu.ft. capacity each, and the dredge is capable of digging to a depth of 45 feet below waterline. A maximum depth of 58 feet has been reached by carrying part of the gravel as bank. Average depth of dredging is 28 feet. Bedrock varies from soft to hard but Ls decomposed enough so that a few inches of it can be taken up. The dredge is held in digging position by a single spud of 32 tons. The trommel is 7 feet in diameter and is perforated with J-inch to -inch holes, but one section of 2-inch mesh is provided for recovery of nuggets. Riffles are of the Hungarian dredge type shod on top with -inch strap iron. The stacker for coarse tailing is 135 feet long and carries a 36-inch belt. The operating crew averages 24 men.

Electric motors are as follows: 50 hp. on a high-pressure 10-inch pump, 50 hp. oil a low-pressure 10-inch pump, 50 hp. on an auxiliary 10-inch pump, 25 hp. on a 4-inch pump, 35 hp. on the winch, 35 hp. on the screen, 50 hp. on the stacker, and a 200-lip. digging motor.

The following figures on operation are furnished through the courtesy of C. M. Derby, consulting engineer. For the fiscal year ending June, 1937, the operating cost under rather severe conditions averaged 4.98 cents per cubic j'ard. This includes labor, material, power, ordinary taxes, and general expense. No land-cost, no royalty, and no deprecia- tion are included. The average monthly yardage was 240,000 cubic yards. The approximate cost of the dredge was $250,000.

When the dredge was operated near the old Chapman mine, recovery of platinum group metals was as high as 2 ounces per week, and pieces weighing as much as half an ounce were recovered. In other locations the recovery was about one-half ounce per week. Analysis of a shipment follows: waste or sand, 38% ; gold, 1.89% ; platinum, 25.78% ; iridium, 10.51%; osmium, 16.21%; ruthenium, 7.71%; palladium, 0.27%. Recovery of platinum from sands removed from the riffles at time of clean-up is made on a long tom on the dredge. The last cleaning is done by panning ; and before the last panning, the concentrate is ground in a small ball mill and then is allowed to stand over night in nitric acid. Among the minerals contained in the concentrate is native cinnabar. The richest sand Is found, and the poorest recovei-y is made in passing through ground that has already been mined. The channel of the river was mined shortly after 1850 in the days of the gold-rush. A dime that looked new, which carried the date 1838, was recently recovered.

C. L. Kalhangh, operated a suction dredge and tractor on the Thurs- day No. 1 mine on Crow Creek from May 1 to September 15, 1942. The yield from 1000 cubic yards of gravel was 103 ounces of gold.

La Grange Placer Mines, Ltd., Box 141, Weaverville, operated its hydraulic mine between Junction City and Weaverville during parts of 1940, 1941, and 1942. In 1941 operations lasted from January 1 to July 1 and from December 16 to 31. The yield from 113,100 cubic yards of gravel was 757 ounces of gold and 84 ounces of silver. Operations conducted from January 1 to July 1, 1942, yielded 548 ounces of gold and 52 ounces of silver from 250,000 cubic yards of gravel.

Lewiston Placers of Lewiston operated its hydraulic mine near Lewiston from January 27 to July 1 and from December 6 to 31, 1941. In 1942 operations from January 1 to June 30 yielded 188 ounces of gold and 24 ounces of silver from 75,000 cubic yards of gravel.

Sec. IV

:MIXES HY tOUNTIEP

102. Lincoln Gold Dredging Company, dragline dredge. Reprinted from CaU- foruia Journal of Mines and Geology, January lO',!, p. ',6.

Lincoln Gold Bvcdoing Conipani/ of Lincoln operated dragline dredges in the Lewiston district in 1941 with the following results : from the Clark-Jansen property the yield from 109,139 cubic yards of gravel was 430 ounces of gold and 67 ounces of silver ; from the Costa property the yield from 26,432 cubic yards of gravel was 134 ounces of gold and 9 ounces of silver; from the Dickerson property the yield from 65,856 cubic yards of gravel was 149 ounces of gold and 16 ounces of silver; from the Fancelli property the yield from 28,170 cubic yards of gravel Avas 141 ounces of gold and 19 ounces of silver ; from the Froloff property the yield from 562,732 cubic ards of gravel was 2453 ounces of gold and 158 ounces of silver ; and from the Phillips property the yield from 194.876 cubic yards of gravel was 1134 ounces of gold and ']61 ounces of silver. One of the dragline excavators was equipped with a 2i-eu.yd. bucket and the other with a 1-cu.yd. bucket. In addition to this production from dragline operations small amounts of gold and silver were recovered by hydraulic operations at the Costa and Phillips properties.

In 1942 operations were continued from January 1 to Septem- ber 12 on the Costa property on Hush Creek with a dragline excavator having a 22-cu.yd. bucket. The yield from 271,744 cubic yards of gravel was 1406 ounces of gold and 95 ounces of silver.

As this dredge has several features that are different in design from those commonly used, the following description is reprinted from the California Journal of Mines and Geology for January 1941:

Lincoln Gold Dredging Company is a partnership of E. M. Clark, French Gulch, and W. K. Jensen, Lincoln, California. Late in 1939, a dragline dredge was installed on a tract of 60 acres held by leases, coA'ering bars on Trinity River, at a point 4 miles west of Lewiston, in sec. 27( ?), T. 33 N., R. 9 W., M. D. It was planned to dredge this

Averill, C. V., op. cit., pp. 45-47.

310 PLACER MINING FOR GOLD IN CALIFORNIA [BuU. 135

tract to a depth of 6 feet to 23 feet. The washing-plant is similar to those made by Bodinson, which have been described in some detail in a preceding chapter, but it is of Clark's own make. It has a capacity of 3500 cubic yards per day, and is driven by a D-13000 Caterpillar diesel engine. A 25-kw. electric generator is provided for lights and for one or two small motors as needed. Main drive is from engine to countershaft by multiple V-belt.

Several improvements on older designs have been incorporated. Disc-wheels, 3f) inches in diameter, are attached to hand-winches instead of cranks. This is a safety measure to prevent the breaking of the operator's arm by a sudden strain which might reverse the direction of rotation of the crank. Beneath the trommel is the usual depressed trough containing baffles to regulate the flow of sand and water to each sluice. In each compartment of this, beneath the surface of the fluid, a jet of water supplied from a manifold impinges against a horizontal plate. Thus the contents of each compartment are kept in a state of agitation, giving the gold a chance to settle out. Clark says that most of his gold is recovered in these traps, and that it is not necessary to clean up the sluices so often. Sluices are equipped entirely with expanded metal lath over coconut matting, no riffles. Near the trommel a few strips of plate for amalgamation (silvered copper), inches wide and as long as the width of the sluice, are placed beneath the expanded metal lath. The pump-screen is in the form of a revolving drum to keep it free of floating trash. Several gates made of heavy steel bars, placed above the tailing stacker, are arranged to open upward only. Boulders traveling up the belt in the normal way pass through readily; but if a round boulder starts to roll back down the belt, it is stopped by one of the gates, and is given a Tiew start in the proper direction. The dragline is a model 85 Northwest with a bucket of 2-cu.yd. capacity. The outfit includes also a Caterpillar tractor equipped with bulldozer.

North Fork Placer Mining Company of Helena operated the North Fork hydraulic mine 1 mile from Helena from January 1 to June 30, 1941. The recovery from 53,500 cubic yards of gravel was 277 ounces of gold and 30 ounces of silver. Operations at this mine in 1939 are described in the California Journal of Mines and Geology" for January 1941. The following description of an earlier period of operation is from Gardner and Johnson : The North Fork placers on Trinity River at Helena were worked under a leasehold during the 1932 season by F. M. Reynolds, W. 0. Kunman, and E. C. Mathews. A fourth man was employed. The mine was operated two 9-hour shifts with two men on a shift. The gravel deposit consisted of an old channel cutting through a ridge. The lower 15 feet of gravel was very tight and partly cemented. It was broken down by first cutting the bedrock from underneath it. After being broken down considerable piping was necessary to disintegrate the cemented fragments. The top gravel washed easily.

"Water was brought to the mine from two sources in different flume lines. The lower flume emptied into a reservoir which supplied a giant

Averill. C. V.. op. cit., pp. 52-53.

Gardner, E. D., and Johnson, C. H., Placer mining in the western United States, Part II, Hydraulicklng, etc. : U.S. Bur. Mines Inf. Circ. 6787, p. S.l, 1934.

Sec. IV] MIN'KS I'.Y COUXTIKS 311

\vitli a r)-iiicli no/./.li' tor a])()iit .") lioiii's' pipiii; a (lay. A pipe line to tlic upjKn- flume supplied one fiant witti a 7-iiieli nozzle steadily. Two had l)i-eaks in tlie Jinnies dui-in<i' tlie season material 1\- inereased the cost ])er enhic yard washed. As the walei- supi)ly decreased the diameters of tlie noz/les were reduced from 7 to (5 inches and fiiudly to f) inches.

Two sluices, consistinji- of seven I'i-foot boxes 48 inches wide were used. One sluice emptied out of one end of the pit throu<ih a bedrock cut varyin<i: up to 30 feet in depth ; the other box went out the ()ii])osite end. The riffles consisted of heavy rails placed crosswise in the boxes on top of 4- by 4-inch timber. An undercurrent was used at the end of the sluice that carried away most of the material. The undercurrent table was 12 by 20 feet and was decked with the type of Hungarian I'ifilles used on dred'cs. Between 800 and 1,000 cubic yards was handled in 18 hours with a full head of water. The averaje daily yardage handled for the season Avas 770 cubic yards. One hundred and fifty thousand cubic yards Avas washed during the season (December 15 to June 30). The labor cost was 3 cents per cubic j'ard ; supplies were estimated at ] ] cents, making a total operating cost of 4i cents. The lessees had no supei'vision or {general costs. The indicated costs do not include deprecia- tion, interest on investment, or amortization.

Oro Trinify Dredging Company, Box 212, Oroville, operated a diesel- ]iowered dragline dredge equipped with excavator using a 1-cu.yd. bucket near Weaverville from January 1 to June 18, 1940. The equip- ment then was moved to the Scott River district, Siskiyou County, where operatioTis were resumed on August 10.

Placer Exploration Company. See Viking Dredging Company.

Red Hill mine is one of the mines operated by Goldfield Consolidated Mines Company and is mentioned above under that heading.

Beddings Creek Placer, Ltd., installed new equipment at the AVallace Bros, mine in sec. 33, T. 32 N., R. 9 W., M.D. The operation is of interest because a Ruble elevator Avas used. It was described in the California Journal of Klines and Geology "' for January-April, 1933, but this is out of print. The following description is from Gardner and Johnson Placer operations on Redding Creek near Douglas City were begun in the spring of 1932 ; 56,600 cubic yards of gravel was washed by the time the water supply failed. The gravel bed, which was 9 feet deep and 120 feet Avide, lay in a creek bottom. The fall of the creek Avas so slight (one- tenth inch to the foot) that enough grade could not be obtained for sluice boxes. A Ruble elcA'ator Avas used for elevating the gravel and boulders and sorting out everything over 2 inches in diameter. Water under a 300-foot head Avas brought to the pit through a 24-inch pipe 3,000 feet long. The Y's in the pit Avere of 15-inch pipe. The gravel AAas cut and sAvept to near the entrance of the Ruble by a giant Avith a 5- or 6-inch nozzle, then the material Avas Avashed up the Ruble by means of a second giant Avith a 5-inch nozzle. A third giant Avith a 3-inch nozzle Avas used intermittently to level off the tailings piles.

The Ruble Avas 8 feet Avide by 60 feet long and elevated the oversize 25 feet. It AA-as lined Avith sheet steel. The grizzlies were of 3- by 6-inch timber set on edge ; the top edge Avas steel-clad. They Avere placed cross- Avise on 3- by 6-inch sills laid lengthwise on the sheet-iron bottom of the

Averill, C. V., Gold deposits of the Redding and AVcaverville quadrangles : Cali- fornia .Tour. Mines and Geology, vol. 29, pp. 68-69, 1933. 8 Op. cit.

PLACER MINING FOR fiOLD IN CALIFORNIA

[Bull. 135

F:g. lO.T. Weaver Dredging Company, dragline dredge. A'-; CdUforma

JonriKil of Mines and Geolofiy, January 19', 1, p. Hi.

chute. Tlie plus 2-in('li material was washed up through the elevator by the giant ; the undersize dropped through the grizzly and ran down the bottom of the chute to four 12-foot boxes, 48 inches wide, set at right angles to the elevator. As the gravel was only 9 feet deep, the Ruble had to be moved three times during the season. With 7 men and a Caterpillar tractor a week was re(iuired to move the elevator to a new location. A second elevator was planned next season to allow continuous production. Boulders were bulldozed; 2,000 pounds of 40-percent-strength gelatin dynamite was u.sed for this purpose during the 1932 season. An average of 540 cubic yards per day was washed during the 1932 season. The operating cost of washing the gravel was 19 cents, of which three-fourths was for labor. The co.st did not include ditch work (other than the ditch tender), construction costs, interest, depreciation, or amortization.

//. S. Smith, R. A. Synith, and R. I. Smith, operated a dragline dredge using a 3-cu.yd. bucket on the High Channel mine in the Hayfork district for 30 days in August and September, 1941. The yield from 100,000 cubic yards of gravel was 300 ounces of gold and 40 ounces of silver. In addition, a small quantity of gold was recovered at this prop- erty by hydraulic mining.

Swanson Mining Corporation of Salyer hydraulicked a small yardage of very high-grade gravel at the Salyer mine between February 9 and May 24, 1940. Operations were continued in 1941. Further details about this property are given under two headings. Salyer Consolidated Mines Company and Swanson Mining Corporation in the California Journal of Mines and Geology for January. 1941. At this mine one ounce of platinum-group metals was recovered for each 20 ounces of gold and an analysis of this is given in the publication cited.

Trinifxj Dredge was operated on the Trinity River at a point about 4 miles north of Lowiston by C. R. and T. D. Harris of Lewiston from

Averill, C. V.. op. cit.. pp. 59-62.

Sec. IV] MINES BY COUNTIES 313

January 1 to November 15, 1940, when the deposit was exhausted. This dredge is described in the California Journal of Mines and Geology for January, 1941.0

Viking Dredging Company, Box 498, Chico, operated a dragline dredge equipped with a 2-cu.yd. bucket throughout 1940 on Filibuster Flat, Shanahan Bar, and Hidden Channel near the confluence of Redding Creek and Trinity River. The company operated the Hidden Channel, Tout, and Gasper properties in the Weaverville district from January 1 to February 28, 1941. Then the operation and equipment were taken over by Placer Exploration Company of Douglas City, which continued operations until December 2. The dragline dredge was equipped with a 2-cu.yd bucket.

Weaver Dredging Company, Box 216, Weaverville, operated a drag- line dredge using a 1-cu.yd. bucket on East Weaver Creek from January 1 to June 12, 1940. Then the equipment was shipped to Montana. The company operated a second dragline dredge equipped with a 2-cu.yd. bucket on La Grange property during parts of 1940. This operation was continued from January 1 to May 19, 1941, and the yield from 231,124 cubic yards of gravel was 976 ounces of gold and 89 ounces of silver.

W. E. Woodbury, hydraulicked 20,000 cubic yards of gravel at the Rex mine east of Weaver Creek, near Weaverville, during 1941.

Tuolumne County

Barker Corporation, Hornitos, operated a dragline dredge on Tuol- umne River near Jacksonville from January 1 until November 18, 1940. Then the equipment was moved to Hornitos, Mariposa County.

Jackass property in the East Belt district was worked by L. R. Harris of Merced with a dragline dredge from April 20 to May 22, 1940.

E. A. Kent, 260 California Street, San Francisco, operated a drag- line dredge with a If-cu.yd. bucket on Six Bit Gulch near Chinese Camp in December 1940. A second dragline dredge equipped with a 2i-cu.yd. bucket was operated on Sanguinetti Ridge near Chinese Camp from June 29 until the end of 1940. Operations with these two dredges were con- tinued in 1941 on the two properties mentioned above and on the Rosasco property. In 1942 operations with the two dredges were continued from January 2 to February 19 with the following results : on the Lyons Ranch 53,000 cubic yards of gravel yielded 224 ounces of gold and 15 ounces of silver; on the Rosasco Ranch 52,500 cubic yards of gravel yielded 308 ounces of gold and 21 ounces of silver.

La Bienvenita mine was operated during 1940 by E, Z, Bowman, Box 6, Chinese Camp, who used a nonfloating washing plant.

Menke-Hess property near Chinese Camp was operated in 1941 by Rio Development Company and' McMillan & Company of Jamestown, who used a nonfloating washing plant.

Mullin & Company, Sonora, washed 55,700 cubic yards of gravel by dragline dredge on Sullivan Creek in 1940 and recovered 419 ounces of gold and 41 ounces of silver.

Mullin-Ilampton Dredging Company of Sonora operated a dragline dredge which had an excavator with 1-cu.yd. bucket on the Kaplan

Averill, C. V., op. cit.. pp. 62-63.

Placer Mixing For Oold Ix California

Bull. 135

Sec. IV] MINES BY COUNTIES 315

(Dondero) mine on Woods Creek 1 mile east of Columbia from January 29 to July 15, 1941. The yield from 85,000 cubic yards of gravel was 365 ounces of gold and 28 ounces of silver.

H. M. Richards did ground .sluicing at Ohio Flat in the Challenge district and recovered 23 ounces of gold from 1000 cubic yards of gravel between January 1 and April 15, 1943.

Yuba County

Arundel Corporation, Box 951, Marysville, produced a substantial quantity of gold in the Smartsville district in 1940 in preparing gravel for concrete aggregate.

Dove Mining Company, Oregonhouse, operated a nonfloating wash- ing plant on the Rose property in 1941.

Parks Bar Company, Box 932, Nevada City, operated a diesel- powered dragline dredge equipped with a l-cu.yd. bucket in Big Ravine in the Smartsville district from May 1 to October 31, 1940. The recovery from 95,000 cubic yards of gravel was 429 ounces of gold and 20 ounces of silver.

R. & M. Mining Company of La Porte operated a dragline dredge using an excavator with a l-cu.yd. bucket at several properties on Slate Creek in the Strawberry Valley district in 1940 and 1941. In 1940 the Corley and Princess Pines properties were worked. In 1941 the Corley property yielded 423 ounces of gold and 36 ounces of silver from 134,000 cubic yards of gravel between April 15 and June 21 ; the Ophir property yielded 76 ounces of gold and 7 ounces of silver from 15,000 cubic yards of gravel between June 21 and July 8 ; and the First Chance property yielded 691 ounces of gold and 60 ounces of silver from 99,000 cubic yards of gravel between July 21 and November 27.

Sunmar Dredging Company, Box 228, Oroville, operated a dragline dredge on property of Mammoth Mining Company in the Smartsville district during 1940. The dragline excavator had a 2-cu.yd. bucket.

Williams Bar Dredging Company, 232 Montgomery Street, San Francisco, or Box 575, Marysville, operated a connected-bucket dredge on the Yuba River 4 miles northwest of Smartsville throughout 1940, 1941, and 1942. The operation was suspended January 13, 1943, under Limitation Order L-208 of the War Production Board. The dredge was equipped with 84 buckets of 6-cu.ft. capacity. In 1942 the yield from 2,872,327 cubic yards of gravel was 6,354 ounces of gold and 447 ounces of silver,

Yuha Consolidated Goldfields, 351 California Street, San Francisco, operated a fleet of six dredges at its property in the Yuba River basin near Hammonton in 1941. All the dredges were equipped with 18-cu.ft. buckets and electric power. Two had 87 buckets each; two had 100 buckets each ; one had 126 buckets ; one had 135 buckets. In 1943 the company was allowed to operate two of the dredges, the one with 126 buckets and the one with 135 buckets.

The following article. Deep Gravels Dredged Successfidly, describes one of these dredges.

PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

Deep Gravels Dredged Successfully

By Herbert Sawin

Modern dredges, as operated by Yuba Consolidated Gold Fields, overcome obstacles today that seemed insurmountable only a few years ago. Early California dredge men considered a digging depth of 60 feet below water level the maximum range of economical bucket-line dredging. Later, owing to new designs and improved materials, 80 feet, then 112 feet, and now 12-1 feet, below water level are profitable operating ranges. Based on experience with Yuba 17, a 3,500-ton gold dredge built-in 1934 and operated at Hammonton, California, which dredged abrasive and tightly packed gravel at depths to 112 feet below water level, Yuba 20 was designed and built for the same field, starting operations on May 1, 1939. This newest addition to a fleet of six 18-cu.ft. dredges digs to a depth of 124 feet below water level, at times against a bank of 50 feet. The contract for Yuba 20 was signed August 4, 1938. The first hull plates were laid in November, and the hull was launched 30 days later. The job was completed, and the dredge operated its first full day, on May 1, 1939. Considering the weight of 3,700 tons, the period of less than eleven months from contract date to starting of the dredge is noteworthy.

Electrically operated and displacing about 3,700 tons, the steel hull, superstructure, and gantries of the dredge alone weigh 1,500 tons. The digging units weigh 860 tons exclusive of gravel and suspersion parts. Its steadiness in the water while digging is noticeable at once to a visitor acquainted with placer mining dredges. The hull measures 250 feet, 8 inches by 80 feet by 11 feet. The digging ladder is 216 feet long and 13 feet f inch deep ; the main stacker measures 225 feet between pulley centers, and carries a 44-inch rubber conveyor belt. With the ladder raised to 30 feet above water, over-all length of the dredge is about 540 feet. These weights and dimensions clearly indicate the hug'e size of the dredge. Perhaps it is easier to visualize a dredge as long as an average citj' block and with its topmost point, the stern gantry, ten stories above the pond surface.

Describing the dredge briefly from ' stem to stern, ' ' principal parts include the following :

1. Manganese-steel, two-piece lower tumbler with nickel-steel shaft.

2. 135 manganese-steel, rivetless-lip buckets.

3. Forged nickel-chromium steel bucket pins.

4. One-piece cast high-carbon-chromium steel upper tumbler having shaft cast integral.

5. Forged nickel-chromium steel tumbler wearing plates.

6. Perry bucket idler mounted on under side of digging ladder.

7. Bucket idler in well.

8. Packed lower ladder suspension blocks.

9. Cast-steel upper and lower block sheaves, 60-inch diameter.

10. Ladder hoist lines, 2-inch wire rope.

11. Monitor on bow to knock down high banks.

Sales Engineer, YuWa Manufacturing Company, San Francisco, California. This article was published in Engineering and Mining Journal, vol. 144, no. 7, for July 1943, and is reprinted by permission of that journal.

(317)

318 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

12. Kc'volviiif screon 50 I'oet G indies Ion*? and 9 feet diameter, using 4-incli Ynba A1{S seroeu plates, and vitll friction drive at lower end.

13. Wincli room on the center line of the dredge with flying bridge extending to both sides.

14. Two-drum hiddei- hoist winch on port side.

15. Eight- swing winch on starboard sick', having separate drums for each of the port and starboard bow lines.

IG. Auxiliary stacker 48 feet long with 44-inch belt to carry over- size material from the screen to main stacker or to rock chutes.

17. 'Main stacker about 18 degrees for normal work, but this can be changed as desii-ed.

18. Double-drum sta<'ker hoist winch driven by a single motor with worm drives.

li). Two spuds, box type. 37 inches by GO inches by 70 feet.

20. Table ai-ca, G,000 s(piare feet, single-bank, double-decked with molded rubber liungarian-type rifilies.

21. Hinged top deck sluices can be raised to clean up lower sluices.

22. Tail sluices extending about 30 feet aft of stern.

23. Auxiliary spill chute aft of screen, permitting rock tailings to be discharged through a well in the stern.

24. Two sand wheels discharging to 30-inch belt conveyors which carry excess sand to the main stacker.

25. Conveyor idlers, troughing and return, of the anti-friction type. Tumps include the following Yuba centrifugal units: one 14-inch,

70-foot head, 5,500 gpm. ; one 14-inch, 52-foot head, 5,500 gpm. ; one 6-inch dual, llG-foot head, 1,100 gpm.; one 4-inch auxiliary, G5-foot head, 450 gpm. ; and a 2-inch service pump. A Yuba mud removal system using an 8-inch Byron-Jackson pump rated at 3,000 gpm., 245- foot head, also furnishes water to the monitor mentioned previously. Total installed load is 2,175 hp., all a.c. power.

Two variable-speed drive motors, each 300 h])., GOO rpm., are situated just aft of the upper tujnbler, one on each side, with V-belts connecting them to the pulley shaft. This arrangement was first tried on Capital No. 4 dredge, built in li)37, where the multiple a.c. motor drive has been entirely satisfactoi\v and resulting in a simple, trouble-free installation. The ladder winch is sei)arate from the nuun drive, thus eliminating the large belt formerh' needed. V-beit drives are also used on the swing winch, screen drive, and main and auxiliary stackers.

The main drive on Ynba 20 has proved to be highly successful. At Ilammonton, about 00 feet below water level, there is a jnirticularly hard (but not cemented) gravel stratum. The drive in question helps materi- ally in solving dredging problems associated with digging hard formations at great depths. The double V-belt main drive provides a flexible unit which acts as a safety link capable of absorbing severe shocks and pro- tecting the rest of the digging unit in the event of sudden or severe over- load. Bucket line speed is 21 per minute, based on the experience of several deep digging dredges in California.

In general, dredges digging 100 feet or more below water level have been found to excavate less material per day than units of the same bucket capacity digging at 80 feet or less. For example. Capital No. 4 dredge,

Sec. IV] DEEP GRAVELS DREDGED SUCCESSFULLY — SAWIN

(li<?frin{? to 82 feet vitll 18-cii.ft. buckets, was capable of turning out 127,- 000 cubic yards of gravel per week, but its most economical rate was set at 100.000 cubic yards. For Yuba Xo. 20, on the other hand, the greatest weekly yardage luis been about 00,000 cubic yards. Reasons for this are the longer time required on the larger dredge for unproductive opera- tions such as raising the ladder, oiling, stepping, and moving, and the less sensitive control the winchman on the larger dredge has over the actual digging. Because of the greater weight of tlie dredge, he is not con.scious of slight variations in digging depth as he would be on a smaller dredge, and it the buckets are not cutting deeply, several minutes will elapse before the half-empty buckets travel up into sight and the winch- man drops the ladder to a correct digging position. With the larger dredge digging is necessarily slower in corners or at other points where caving might cause serious accidents. A further factor in the yardage dug by Yuba No. 20 is the tight formation mentioned in the foregoing. Successful deep dredging owes much to the use of an idler to control the catenary of the bucket line in its return to the lower tumbler. A Perry pateiited idler, named for its inventor, 0. B. Perry, was first used on Yuba 17 at Ilammonton, California. Yuba 20 is also equipped with one. It is a cylindrical device, wheel-like in design, mounted on the underside of the digging ladder about midway between the tumblers. The buckets ride upside down over the idler, the contour of the face fitting the bucket lips. Renewable cast manganese-steel wearing plates are provided on the idler itself, and renewable forged nickel-chromium steel wearing bars protect the steel suspension unit. Both wearing plates and bars show little wear after many months of use, and because the long bucket line is better balanced, wear on bucket pins, bushings, and tumbler plates is reduced noticeably. The Perry idlers on Yuba's 17 and 20 make it possible to use buckets and bucket pins of the same design and metal sections as on shallower digging dredges in the same field, and buckets and pins are therefore interchangeable on all dredges in use in this field.

The Yuba mud removal system, also a help in deep dredging, pro- vides suction behind the lower tumbler in the form of a pipe line inside the digging ladder with a flexible hose coupling to a pump on deck. On Yuba 20, a "Y" arrangement of gate valves permits discharge of mud pumped from the pond bottom either tlirough a pipe line carried by the main stacker to a point far beyond the face of the rock tailings, or by a floating pipe line away from the dredge to a point several thousand feet distant, where the mud can be used for filling old holes or basins. In these basins muddy water can settle and be filtered through tailing piles to avoid stream discoloration. The mud sometimes reaches a depth of 30 feet on the bottom of the pond, crowding the lower tumbler and unless removed prevents free swinging of the dredge.

Auxiliary stacking and other stern-end equipment also attract favorable attention of experienced dredge operators. A well is provided on the center line of the hull at the stern, through which rock tailings can be discharged to make anchorage for the spuds, a departure made desirable by the length of the dredge. This is believed to be the first dredge so built. Part of the sand tailings are discharged to the main stacker belt to aid in binding rock tailings. The stacker was first used at an elevation of 23 degrees, the high elevation being necessary during

PLACKR MININO FOR GOLD IX CALIFORNIA [Bull.l.Sr

nii*-"TTTTT

See. IV] DEEP GRAVELS DREDGED SUCCESSFULLY — SAWIN 321

early operations until tlie pond became deep enough to dispose of rock tailiiijrs witliout sucli hili stacking.

Deep dredging methods miist be developed to suit conditions that are decidedly different fi'om those encountered in shallow dredging. An imi)()rtant change is in the design of the ladder hoist winch. On Yuba 20, this unit is separated from the main drive and occupies a deck space measuring 29 by 14 feet on the port side of the deck just inside the house. The total weight of the wincli, including structural steel base, brake assembly, etc., is al)out 63 tons. The two ladder hoist lines are 2-inch wire rope on separate drums. licngth of each is 2,300 feet. Each drum weighs 12 tons, and is driven tlwough a pinion shaft which also carries the mechanical brake wheel. All shafts used on the winch assembly are nickel steel.

Power is supplied by a ."jOO-lip., 1,160-rpm. type "CW" Westing- house motor e(|uiiiped with a Westinghouse Thrustor brake type HI-198, and operating through a Farrel speed reducer with a ratio of 7.181:1. All pinions and gears have herringbone cut teeth. The mechanical brake is of the post type, actuated by releasing pressure in a 10- by 10-inch Westinghouse air cylinder, counterweighted. Brakes are electrically operated and manually controlled from the pilot house. Manual control gives the winchman a finer "feel" and saves possible damage to equip- ment which might occur with full automatic brakes. The braking action, tiirough the brake wheel to the drive pinion-s, slows down and stops both drums simultaneously. Immediately following the mechanical brake action, the Thrustor brake on the motor is applied automatically. A Lilly control is provided as a safety measure. Should the ladder be i-aised or lowered beyond safe limits or accidentally be dropped too fast, this unit would take control out of the winchman 's hands and apply the brakes automatically. This type of control a.ssures a longer life for winch parts. Internal expanding type clutches are used and are oper- ated pneumatically from the pilot house. With drums revolving at a speed of 7.46 rpm., the raising and lowering speed for the digging ladder is about 12 vertical feet per minute at the lower tumbler.

The swing winch on Yuba 20 is on the starboard side just inside the front end of the house. The bow-line drums can be operated inde- pendently of the other drums on the winch, and a separate drum is used for each of the bow starboard swing lines. Other drums on the winch include two stern-line drums, two spud-line drums, and two spares. Clutches on all the drums are of internal expanding type controlled electrically through pneumatic cylinders mounted on the winch frame. The application of air cylinders to dredge equipment was originally developed and patented by Yuba about ten years ago for use on dredges to be operated in the tropics. Manually operated brakes are provided fen- the same reason as used on the ladder hoist winch. The winchman has better control in applying them, thus avoiding shocks to lines and thereby increasing the life of the wire rope.

TJie history of dredge mining proves that successful dredges are especially designed to suit conditions to be overcome in a particular field. There is practically no so-called "standard dredge." This applies in pai-ticular to deep-digging dredges, which present problems entirely dif- ferent from those connected with shallow dredging. Smaller yardage with a given size of bucket naturally reduces the gro.ss income.

322 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

The initial biprh cost of a dredjro like Yuba 20 burdens the cost of operation, and properties sufTu-iently larjjre to eai-ry the load of such an investment are not found often. Meehanically, the limit in size for mining dredges has not been reached. Pconomie problems which affect the cost of dredging are the main factors limiting meciianical size at present.

An 18-cu.ft. dredge in California digging 80 feet below water level operates at a field cost of less than 3 cents per cubic yard. Beyond 80- foot digging depth, the operating cost rises sharply, and for dredges digging 100 to 120 feet, the field cost is nearer to 5 cents per cubic yard. This rising cost must be given serious thought when considering a deej) dredging venture, one reason being that areas large enough and deep enough to warrant the investment, probably would not have a high aver- age value per yard. For profitable deep dredging, the maximum dredg- ing depth would be determined by an anticipated return commensurate with the extra operating costs. It is probable that mechanical improve- ments and changes will be developed which may result in dredges of larger daily capacities with a given size of bucket, and do so economically, making otherwise worthless ground valuable mining property.

Operating data on Yuba 20 have been furnished by Yuba Con- solidated Gold Fields, and with thanks to tliat company the following information is made available: Daily operating time (three shifts) has averaged 21 hours and 29 minutes. This makes full allowance for shut- dowiLs for all reasons, including moving, ladder inspections, clean-uji, repairs, and greasing. Gravel dug has averaged 12,260 cubic j'ards per day at a field cost of 4.32 cents per cubic yard. The weekly power con- sumption has been about 145,000 kw.-hr.

On page ')! of this bulletin the gold mining tables as installed origi- nally on Yuba Xo. 20 are deseribed. Kec-ent experience with Yuba Xo. 20 in digging through old rock piles and underlying sand beds from older operations pointed to a jieriodie excess of sand and greater (|uanti- tics of fine gold. This condition was caused by concentrations from dredges operating in the same area at jirior times which could not dig as deep as Xo. 20. To meet tliis condition jigs were jirojiosed for use instead of i-iffles. Exiiaustive studies wei-e made to improve the recovery factor as a means of counteracting increased opei'ating expense.

liefore installing jigs, however, a thoi-ougli test was conducted. The exti-emely high volume of sand enconntei-ed at times i)roduced ditficult material handling conditions for jigs. Yuba jigs used experimentally proved to be capable of efficient operation. A full set of jigs designed aiul built by Yuba Manufacturing Company was installed on Yuba Xo. 20 in late 1!)4(). The Yuba jig is of the horizontal thrust design with a small motor moinited between and operating two cells. The eccentric drives are com|)letely enclosed and run in oil with heavy roller bearings used to red\ice wear and to pi'ovide long operating life. Headroom recpiirenients are kept to a minimum because of the horizontal tlirusi and this feature is of gi-eat advantage under di-edge ojx'rating conditions.

There are twelve 4-cell rougher jigs and two 4-cell cleaner jigs on Yuba Xo. 20 and the complete circuit includes a ball mill and a small area of liffles over which jig concentrates are run. The gold recovery factor has been imj)roved sufficiently to justify the change from riffles, even though an extra man per shift is needed to operate the jigs and auxiliai-y mechanical e(iuipnuMit installed on Yuba Xo. 20 to replace tables.

Appendix

Laws Affecting Placer Mining

A few laws that apply particularly to placer mining are brought together here for ready reference from a number of different publica- tions. For detailed information on other phases of mining law, refer- ence should be made to Bulletin 123, American Mining Law', and Bulletin 127, Manner of Locating and Holding Mineral Claims in Cali- fornia.

1 Ricketts, A. H., American mining law: California Div. Mines Bull. 123, pp. 1-1018, 1943.

2 Ricketts, A. H., Manner of locating and holding mineral claims in California (with forms) : California Div. Mines Bull. 127, pp. 1-35, with revisions by C. A. Logan, March 1944.

The Caminetti Law

An Act to create the Calif ornia Debris Commission and regulate hydraulic mining in the State of California.

(Approved March 1, 1893.)

Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, That a commission is hereby created, to be known as the California Debris Commission, con- sisting of three members. The President of the United States shall, by and with the advice and consent of the Senate, appoint the commission from officers of the Corps of Engineers, United States Army. Vacan- cies occurring therein .shall be filled in like manner. It shall have the authority, and exercise the poAvers hereinafter set forth, under the supervision of the Chief of Engineers and direction of the Secretary of War.

Sec. 2. That said commission shall organize within thirty days after its appointment by the selection of such officers as may be required in the performance of its duties, the same to be selected from the mem- bers thereof. The members of said commission shall receive no greater compensation than is now allowed by law to each, respectively, as an officer of said Corps of Engineers. It shall also adopt rules and regula- tions not inconsistent with law, to govern its deliberations and prescribe the method of procedure under the provisions of this Act.

Sec. 3. That the jurisdiction of said commission, in so far as the same affects mining carried on by the hydraulic process, shall extend to all such mining in the territory drained by the Sacramento and San Joaquin river systems in the State of California. Hydraulic min- ing, as defined in section eight hereof, directly or indirectly injuring the navigability of said river systems, carried on in said territory other than as permitted under the provisions of this Act, is hereby prohibited and declared unlawful.

Sec. 4. That it shall be the duty of said commission to mature and adopt such plan or plans, from examinations and surveys already made and from such additional examinations and surveys as it may deem necessary, as wall improve the navigability of all the rivers com- prising said systems, deepen their channels and protect their banks. Such plan or plans shall be matured a view of making the same effective as against the encroachment of and damage from debris result- ing from mining operations, natural erosion, or other causes, a view of restoring, as near as practicable and the necessities of commerce and navigation demand, the navigability of said rivers to the condition existing in eighteen hundred and sixty, and permitting mining by tKe hydraulic process, as the term is understood in said State, to be carried on, provided the same can be accomplished without injury to the navi- gability of said rivers or the lands adjacent thereto.

Sec. 5. That it shall further examine, survey, and determine the utility and practicability, for the purposes hereinafter indicated, of storage sites in the tributaries of said rivers and in the respective branches of said tributaries, or in the plains, basins, sloughs, and tule and swamp lands adjacent to or along the course of said rivers, for the storage of debris or Avater or as settling reservoirs, with the object of

326 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

usinf? the same by either or all of these methods to aid in the improve- ment and protection of said navip:able rivers by preventing;: deposits therein of debris resultinj; from mininpr operations, natural erosion or other causes, or for affording relief thereto in flood-time and providing sufficient water to maintain scouring force therein in the summer season ; and in connection therewith to investigate such hydraulic and other mines as are now or may have been worked by methods intended to restrain the debris and material moved in operating such mines by impounding dams, settling reservoirs, or otherwise, and in general to make such study of and researches in the h'draulic mining industry as science, experience, and engineering skill may suggest as practicable and useful in devising a method or methods whereby such mining may be carried on as aforesaid.

Sec. 6. That the said commission shall from time to time note the conditions of the navigable channels of said river systems by cross- section surveys or otherwise, in order to ascertain the effect therein of such hydraulic mining operations as may be permitted by its orders and such as is caused by erosion, natural or otherwise.

Sec. 7. That said commission shall submit to the Chief of Engi- neers, for the information of the Secretary of War, on or before the fifteenth day of November of each year, a report of its labors and trans- actions, with plans for the construction, completion, and preservation of the public works outlined in this Act, together with estimates of the cost thereof, stating what amounts can be profitably expended thereon each year. The Secretary of War shall thereupon submit same to Congress on or before the meeting thereof.

Sec. 8. That for the purposes of this Act "hydraulic mining" and "mining by the hydraulic process" are hereby declared to have the meaning and application given to said terms in said State.

Sec. 9. That the individual proprietor or proprietors, or in case of a corporation its manager or agent appointed for that purpose, owning mining ground in the territory in the State of California mentioned in section three hereof, which it is desired to work by the hydraulic process, must file with said commission a verified petition, setting forth sucli facts as will comply with law and rules prescribed by said commission.

Sec. 10. That said petition shall be accompanied by an instrument duly executed and acknowledged, as required by the law of the said State, whereby the owner or owners of such mine or mines surrender to the United States the right and privilege to regulate by law, as provided in this Act, or any law that may hereafter be enacted, or by such rules and regulations as may be prescribed by virtue thereof, the manner and method in which the debris resulting from the working of said mine or mines shall be restrained, and what amount shall be produced therefrom ; it being understood that the surrender aforesaid shall not be construed as in any \yay affecting the right of such owner or owners to operate said mine or mines by any other process or method now in use in said State; provided, that they shall not interfere with the navigability of the afore- said rivers.

Sec. 11. That the owners of several mining claims situated so as to require a common dumping ground or dam or other restraining works for the debris issuing therefrom in one or more sites, may file a joint petition setting forth such facts, in addition to the requirements of

Appendix] laws affecting placer mining 327

section nine hereof ; and where the owner of a hydraulic mine or owners of several such mines have and use common dumping sites for impound- ing dehris or as settling reservoirs, which sites are located below the mine of an applicant not entitled to use same, such fact shall also be stated in said petition. Thereupon the same proceedings shall be had as provided for herein.

Sec. 12. A notice specifying briefly the contents of said petition, and fixing a time previous to which all proofs are to be submitted, shall be published by said commission in some newspaper or newpapers of general circulation in the communities interested in the matter set forth therein. If published in a daily paper, such publication shall continue for at least ten days ; if in a weekly paper, in at least three issues of the same. Pending publication thereof said commission, or a committee thereof, shall examine the mine and premises described in such petition. On or before the time so fixed all parties interested, either as petitioners or contestants, whether miners or agriculturists, may file affidavits, plans, and maps in support of their respective claims. Further hearings, upon notice to all parties of record, may be granted by the commission when necessary.

Sec. 13. That in case a majority of the members of said commission within thirty days after the time so fixed, concur in a decision in favor of the petitioner or petitioners, the said commission shall thereupon make an order directing the methods and specifying in detail the manner in which operations shall proceed in such mine or mines ; what restrain- ing or impounding works, if facilities therefor can be foiind, shall be built, and maintained; how and of what material; where. to be located; and in general set forth such further requirements and safeguards as will protect the public interests and prevent injury to the said navigable rivers, and the lands adjacent thereto ; with such further conditions and limitations as will observe all the provisions of this Act in relation to the working thereof and the payment of taxes on the gross proceeds of the same ; provided, that all expense incurred in complying with said order shall be borne by the owner or owners of such mine or mines.

Sec. 14. That such petitioner or petitioners must within a reason- able time present plans and specifications of all works required to be built in pursuance of said order, for examination, correction, and approval by said commission; and thereupon work may immediately, commence thereon under the supervision of said commission or repre- sentative thereof attached thereto from said Corps of Engineers, who shall inspect same from time to time. Upon completion thereof, if found in every respect to meet the requirements of the said order and said approved plans and specifications, permission shall thereupon be granted to the owner or owners of such mine or mines to commence mining opera- tions, subject to the conditions of said order and the provisions of this Act.

Sec. 15. That no permission granted to a mine owner or owners under this Act shall take effect, so far as regards the working of a mine, until all impounding dams or other restraining works, if any are pre- scribed by the order granting such permission, have been completed and until the impounding dams or other restraining works or settling reservoirs provided by said commission have reached such a stage as, in the opinion of said commission, it is safe to use the same ; provided, how-

328 PLACKR MINING FOR GOLD IN CALIFORNIA [BuU. 135

ever, that if said commission shall be of the opinion that the restraining and other works already constructed at the mine or mines shall be suf- ficient to protect navigable rivers of said systems and the work of said commission, then the owner or owners of such mine or mines may be permitted to commence operations.

Sec. 1G. That in case the joint petition referred to in section eleven hereof is granted, the commission shall fix the respective amounts to be paid by each owner of such mines toward providing and building neces- sary impounding dams or other restraining works. In the event of a petition being filed after the entry of such order, or in case the impound- ing dam or dams or other restraining works have already been con- structed and accepted by said commission, the commission shall fix such amount as may be reasonable for the privilege of dumping therein, which amount shall be divided between the original owners of such impounding dams or other restraining works in proportion to the amount respectively paid by each party owning the same. Tlie expense of maintaining and protecting such joint dam or works shall be divided among mine owners using the same in such proportion as the commission shall determine. In all cases where it is practicable, restraining and impounding works are* to be provided, constructed, and maintained by mine owners near or below the mine or mines before reaching the main tributaries of said navigable waters.

Sec. 17. That at no time shall any more debris be permitted to be washed away from any hydraulic mine or mines situated on the tribu- taries of said rivers and the respective branches of each, worked under the provisions of this Act, than can be impounded within the restraining works erected.

Sec. 18. That the said commission may at any time, when the condition of the navigable rivers, or when the capacities of all impound- ing and settling facilities erected by mine owners, or such as may be provided by Government authority, requires same, modify the order granting the privilege to mine by the hydraulic mining process so as to reduce amount thereof to meet the capacities of the facilities then in use, or if actually required in order to protect the navigable rivers from damage, may revoke same until the further notice of the commission.

Sec. 19. That an intentional violation on the part of a mine owner or owners, company, or corporation, or the agents or employees of either, of the conditions of the order granted pursuant to section thirteen, or such modifications thereof as may have been made by said commission, shall work a forfeiture of the jn-ivilegos thereby conferred, and upon notice being served by the order of said commission upon said owner or owners, company, or corporation, or agent in charge, work shall immedi- ately cease. Said commission shall take necessary steps to enforce its orders in case of the failure, neglect, or refusal of such owner or owners, company, or corporation, or agents thereof, to comply therewith, or in the event of any person or persons, company, or corporation working by said process in said territory contrary to law.

Sec. 20. That said commission, or a committee therefrom, or officer of said corps assigned to duty under its orders, shall, whenever deemed necessary, visit said territory and all mines operating under the pro- visions of this Act. A report of such examination shall be placed on file.

Appendix] laws affectixg placer mining 329

Sec. 21. That the said commission is hereby granted the right to use any of tlie public lands of the United States, or any rock, stone, timber, trees, brush, or material thereon or therein, for any of the purposes of this Act ; that the Secretary of the Interior is hereby authorized and requested, after notice has been filed with the Commissioner of the Gen- eral Land Office by said commission, setting forth what public lands are required by it under the authority' of this section, that such land or lands shall be withdrawn from sale and entry under the laws of the United States.

Sec. 22. That any person or persons who willfully or maliciously injure, damage, or destroy, or attempt to injure, damage, or destroy, any dam or other work erected under the provisions of this Act for restrain- ing, impounding, or settling: purposes, or for use in connection therewith, shall be guilty of a misdemeanor, and upon conviction thereof shall be fined not to exceed the sum of five thousand dollars or be imprisoned not to exceed five years, or by both such fine and imprisonment, in the discretion of the court. And any person or persons, company, or corpor- ation, their agents or employees, who shall mine by the hydraulic process, directly or indirectly injuring the navigable waters of the United States, in violation of the provisions of this Act, shall be guilty of a misdemeanor, and upon conviction thereof shall be punished by a fine not exceeding, five thousand dollars, or by imprisonment not exceeding one year, or by both such fine and imprisonment in the discretion of the court ; pro- vided, that this section shall take effect on the first day of May, eighteen hundred and ninety-three.

Sec. 23. That upon the construction by the said commission of dams or other works for the detention of debris from hydraulic mines and the issuing of the order provided for by this Act to any individual, company, or corporation to work any mine or mines by hydraulic process, the individual, company, or corporation operating thereunder working any mine or mines by hydraulic process, the debris from which floAvs into or is in whole or in part restrained by such dams or other works erected by said commission, shall pay a tax of three per centum on the gross proceeds of his, their, or its mine so worked, which tax of three per centum shall be ascertained and paid in accordance with regulations to be adopted by the Secretary of the Treasury, and the Treasurer of the United States is hereby authorized to receive the same. All sums of money paid into the Treasury under this section shall be set apart and credited to a fund to be known as the "Debris Fund," and shall be expended by said com- mission under the supervision of the Chief of Engineers and direction of the Secretary of "War, in addition to the appropriations made by law, in the construction and maintenance of such restraining works and settling reservoirs as may be proper and necessary; provided, that said commission is hereby authorized to receive and pay into the Treasury from the owner or OAAiiers of mines worked by the hydraulic process, to whom permission may have been granted so to work under the provisions hereof, sucli money advances as may be offered to aid in the construction of such impounding dams or other restraining works, or settling reser- voirs, or sites therefor, as may be deemed necessary by said commission to protect the navigable channels t)f said river systems, on condition that all moneys so advanced shall be refunded as the said tax is paid into the

330 PLACER MINING FOR GOLD IN CALIFORNIA [Bull. 135

said Debris Fund ; and provided further, tliat in no event shall the Gov- ernment of the United States be held liable to refund same except as directed by this section.

Sec. 24. That for the purpose of securinji; harmony of action and economy in expenditures in the Avork to be done by the Iiited States and the State of California, respectively, the former in its plans for the improvement and protection of the navi<;able streams, and to i)revent the depositin}; of mininjr debris or other materials \vithin the same, and the latter in its plans authorized by law for the ret-lamation, drainaf:?e, and protection of its lands, or rclatin*; to the workinj? of hydraulic mines, the said commission is empowered to consult thereon with a commission of engineers of said State, if authorized by said State for said purpose, the result of such conference to be reported to the Chief of Engineers of the United States Army, and, if by him approved, shall be followed by said commission.

Sec. 25. That said commission, in order that .such material as is now or may hereafter be lodged in the tributaries of the Sacramento and San Joaquin river .systems resulting from mining operations, natural erosion, or other causes, shall be prevented from injuring the said navig- able rivers, or such of the tributaries of either as may be navigable, and the land adjacent thereto, is hereby directed and empowered, when appro- priations are made therefor by law, or sufficient money is deposited for that purpose in said Debris Fund, to build at such points above the head of navigation in said rivers and on the main tributaries thereof, or branches of such tributaries, or at any place adjacent to the same, whicli, in the judgment of said commission, will effect said object (the same to be of such material as will insure safety and permanency), such restraining or impounding dams, and settling reservoirs, Avith such canals, locks, or other works adapted and re(|uired to complete tiie same. The recommendations contained in Exei-utive Document numbered two hun- dred and sixty-seven, Fifty-first Congress, second session, and Executive Document numbered ninety-eight, FortA'-seventh Congress, first session, as far as they refer to imi")ounding dams, or other restraining works, are hereby adopted, and the same are directed to be made the basis of operations. The sum of fifteen thousand dollars is hereby appropriated from moneys in the Treasury not otherwise appropriated, to be imme- diately available to defray the expenses of said commission.

Appendix] laws affecting placer mining 331

AMENDMENTS TO THE CAMINETTI ACT Amendment to the 'Caminetti Act,' 1907

Chap. 2077. An Act To amend section thirteen of an Act of March first, eighteen hundred and ninety-three, entitled "An Act to create the California Debris Commission and regulate hydraulic mining in the State of California."

Be it enacted hy the Senate and House of Representatives of the United States of America in Congress assembled, That section thirteen of an Act of March first, eighteen hundred and ninety-three, entitled "An Act to create the California Debris Commission and to regulate mining in the State of California," is hereby amended so as to read as follows :

"Sec. 13. That in case a majority of the members of said commis- sion, within thirty days after the time so fixed, concur in the decision in favor of the petitioner or petitioners, the said Commission shall there- upon make an order directing the methods and specifying in detail the manner in which operations shall proceed in such mine or mines ; what restraining or impounding works, if any, if facilities therefor can be found, shall be built and maintained ; how and of what material ; where to be located ; and in general set forth such further requirements and safeguards as will protect the public interests and prevent injury to the said navigable rivers and the lands adjacent thereto, with such further conditions and limitations as will observe all the provisions of this Act in relation to the working thereof and the payment of taxes on the gross proceeds of the same : Provided, That all expenses incurred in complying with said order shall be borne by the owner or owners of such mine or mines: And provided further, That where it shall appear to said Com- mission that hydraulic mining may be carried on without injury to the navigation of said navigable rivers and the lands adjacent thereto, an order may be made authorizing such mining to be carried on without requiring the construction of any restraining or impounding works or any settling reservoirs: And provided also, That where such an order is made a license to mine, no taxes provided for herein on the gross pro- ceeds of such mining operations shall be collected. ' '

Approved, February 27, 1907.

Amendment to the 'Caminetti Act,' 1934

An Act to amend the Act entitled "An Act to create the California Debris Commission and regulate hydraulic mining in the State of Cali- fornia", approved March 1, 1893, as amended.

Be it enacted hy the Senate and House of "Representatives of the United States of America in Congress assembled, That section 18 of the Act entitled "An Act to create the California Debris Commission and regulate hydraulic mining in the State of California" approved March 1, 1893, as amended (U. S. C, title 33, sec. 678), is amended to read as follows :

"Sec. 18. The said commission may, at any time when the condi- tion of the navigable rivers or when the capacities of all impounding and settling facilities erected by mine owners or such as may be provided by Government authority require same, modify the order granting the privi- lege to mine by the hydraulic mining process so as to reduce the amount thereof to meet the capacities of the facilities then in use ; or, if actually

;{32 PI-ACKH MINIXC lOU COLD IN CALIFORNIA [Hull. IM.")

required in order to protect the navijrable rivers from dainafre or in case of failure to pay the tax prescribed In- section 23 hereof within thirty days after same hccome.s due, may revoke same until the further notice of the commission."

Hec. 2. Section 23 of sudi Act as amended (U. S. C, title 33, see. 683). is amended to read as follows :

"Si:('. 23. Upon the coiisti'uctiou by the said commission of dams or other works for the detention of debris from liydranlic mines and the issuiiifJT of the order provided for by this Act to any individual, company, or corporation to work any mine or mines by hydraulic process, the individual company, or corporation operatinj? thei'eunder workin<? any mine or mines by liydranlic process, the debris from which flows into or is in whole or in part restrained by such dams t)r other works erected by said commission, sliall pay for each cubic yard mined from the natural bank a tax equal to the total cajiital cost of tlie dam, reservoir, and rights of way divided by the total capacity of the reservoir for the restraint of debris, as (btermined in each case by the California Debris Commission, which lax shall be paid annually on a date fixed by said commission and in accordance with refiulations to be adopted by the Secretary of the Treasury, and the Treasurer of the United States is hereby authorized to receive the same. All sums of money paid into the Treasury under this section shall be set apart and credited to a fund to be known as the debris fund, and shall be expended by said commission under the super- vision of the Chief of Eujiineers and direction of the Secretary of War, for repayment of any funds advanced by tlie Federal Government or other a<ency for the construction of restraining works and settling reser- voirs, and for maintenance: Proridcd, That said commission is hereby authorized to receive and i)ay into the Treasury from the owner or dwnei-s of mines wcu'ked by the hydraulic process, to whom permission may have been granted .so to woi'k under the provisions thereof, such money advances as may be' ofT'>rt>d to aid in the construction of sudi im|)oun(ling (buns, oi- other restraining works, or settling reservoirs, or sites therefor, as may be deemed necessary l)y .said commission to protect the navigable channels of said i-iv(M- systems, on condition that all moneys .so advanced shall he refiiiKled ;is the said tax is paid into the said debi'is fund: .l//f/ i)nirii!((I fiirllK r. That in no e\eiit shall the (lovernment of the United States be liehl liable to reliind sani<' except as directed by this section."

Appr..v.'d..Iuiic l!t. l!i.!4.

Amendment to the 'Caminetti Act,' 1938

All iicl III iiiiiciid secfiou 23 of llic Act to cniilc llic ('iilifi)riii(i Dihn's (onmiision, hm (inu nihil.

Ill it I iiiichil hjf Ihr Siiutfc (Did House of Rrprcsnitativcs of the I' nil id Stalls of Ann rini in Cont/ assfmlthd, That Section 23 of the Act approved March U UI)3. entitled "An Act to create the California Debris Commission and regulate hydraulic mining in the State of Cali- fornia", as ameiKb'd by the Act apjiroved June ]!), 1034, is hereby further amended by adding at the eiul thereof the following: "The Secre- tary of War is authorized to enti-r into contracts to sujiply storage for watei- and use of outlet facilities from debris storage reservoirs, for domestic and ii-rigation purposes and power (b>velopnient upon such con- ditions of delivery, use, and payment as he ma\- a|)prove : Provided, Tiiat

Al)i)endix] laws Ai'KKcrixd i'i,A(i:ii AriMNd '.]:]'.]

the moneys I'occivcd from .such (Mmli- shall he deposited to the ci-edit of tlie reservoir project t'roiii which the watci' is supplied, and the total capital eost of said reservoir, which is to he i-epaid l)y tax ou iiiiuiu' operations as hei-eiu provided, shall he reduced iu the ainount so received."

A|)proved, June 2-"), lt);{S.

Definition Of Hydraulic Mining-

"Ilydi'aulic iniinui;" is the ])rocess by which a hauk of jiohUbeariu' earth and rock is excavated l)\' a jet of water, di,schai-ed through the e()nver*i'in<,f nozzle of a pijx' uudei- a ;4reat pressure, the earth or debris beinji- carried uwa\- by the .same watei-, thi-oub sluices, and disehar<>-ed on lower levels into the natural streams and water courses below; wliei'e the i-avel or other material of tlie baidc is cemented, or wdiere tlie bank is composed of masses of pipe-clay, it is .shattered by blastin' with powder.

DEFINITION OF HYDRAULIC MINING FROM CALIFORNIA CIVIL CODE 1425. i\reaiHn<ir of hydraulic nunin Hydraulic mininjjj Avithin the meaning of this title, is nn'idng by means of the a])plieation of watei', under i)ressure, tln-oug'h a nozzle, against a natural bank.

Kicketls, A. AiiuTiraii .Miniim l-aw; Calif'ipiu .\liiMs ISiiU. 11':;, i). I'.i,

334 I'LACMK MININt; FOR (lOI.r) IN CATJFOriMA f Rull. 1 3.1

Trinity And Klamath River Fish And Game District

The following are from the Fish and Game Code :

97. Trinity and Klamath Kiver district. Tiie following shall con- stitnte the Trinity and Klamath River fish and game district : The Kla- math River and the waters thereof, following its meanderings from the month of the Klamath River in Del Norte County to its contluenee with the Salmon River, and also the Trinity River and the waters thereof, following its meanderings from its confluence the Klamath River in the County of Ilumholdt to its confluence with the south fork of the said Trinity River.

482. (a) It is unlawful to conduct any mining operations in the Trinity and Klamath River Fish and Game District between July 1st and November .'{Otii, both dates inclusive, except when the debris, substances, tailings or other effluent from such operations do not and can not pass into the waters in said district.

(b) It is unlawful between July 1st and November 30th, both dates inclusive, to pollute, muddy, contaminate, or roil the waters of the Trinity and Klamath River Fish and Game District. It is uidawful between said dates to deposit in or cause, suffer, or procure to be deposited in, permit to pass into or place where it can pass into said waters, any debris, substance or tailings from hydraulic, placer, milling or other mining operation affecting the clarity of said waters. The clarity of said waters shall be deemed affected when said waters at a point a dis- tance of one mile below the confluence of the Klamatli River and tiie Salmon River or at a point a distance of one mile below the confluence of the South Fork of the Trinity River and the Trinity River contain fifty (50) parts per million, by weight, of suspended matter, not includ- ing vegetable matter in suspension and suspended matter occurring in said stream or streams due to an act of God.

(e) It is unlawful, between July 1st and November 30th, both dates inclusive, to carry on or operate any hydraulic mine of any kind on, along, or in any waters flowing into said Trinity and Klamath River District; provided, however, nothing herein contained shall prevent the operation of a liydraulic mine wliere the tailings, substance, or debris, or other effluent therefrom does not or will not pass into said waters of said Trinity and Klamath River Fish and Game District, between said dates, and provided further that any person, firm or corporation engaged in hydraulic mining shall have the right until the fifteenth day of July to use water for the purpose of cleaning up.

(d) Any structure or contrivance wliieh cau.ses or contributes, in whole or in part, to the condition, tlie causing of wliich is in this section l)rohibited, is a public nuisance, and any person, firm or corporation maintaining or permitting the same shall be guilty of maintaining a public nuisance, and it shall be the duty of the district attorney of the county where the condition occurs or the acts creating the public nuisance occur, to bring action to abate such public nuisance.

(e) Any person, firm, or corporation violating any of the provisions of this section is guilty of a misdemeanor.

(Amended by Ch. 7G0, Stats. 1939.)

Appendix] laws affecting placer mining 335

Protection Of Domestic Water Supplies

The following is from the appendix of the Fish and Game Code, 33d edition, 1943-45, p. 239:

Section 1. Any person, firm or corporation, other than placer mine operators who hold permits from the California Debris Commission to operate, who has been engaged or who shall engage in the operation of a placer mine on any stream or on the watershed of any stream tributary directly or indirectly to the Sacramento or San Joaquin rivers shall record in the office of the county recorder of the county in which its mine is situate, within 60 days from and after the effective date. of this act, or, if operations are commenced after the effective date, then within 30 days after the commencement of such operations, a verified statement verified by the operator or by some one in behalf of the operator, showing :

(1) A description of the ground proposed to be mined by placer mining methods, described by United States Government subdivisions where possible.

(2) The names and addresses of the owners of the ground.

(3) The names and addresses of the operators of the mine.

(4) The proposed means or method of placer mining operation.

(5) The means which the operator proposes to use to prevent the pollution of any stream by the effluent from such operations.

In the event an owner or operator changes his address, or of a trans- fer of ownership or change of operator of any such mining property ,then within 10 days after any such transfer or change, a notice setting forth the names and addresses of the new owners or operators shall be filed in the office of the county recorder.

Sec. 2. No placer mining operator who does not hold a permit to operate from the California Debris Commission shall mine by placer process on any stream or on the watershed of any stream tributary directly or indirectly to the Sacramento or San Joaquin rivers without taking the following precautions to prevent pollution of the stream by the effluent from operations :

( 1 ) Constructing a settling pond or ponds of sufficient size to per- mit the clarification of water used in the mining processes before the water is discharged into the stream.

(2) Mixing with the effluent from mining operations aluminum sul- phate and lime, or an equivalent clarifying substance which will cause the solid material in the effluent to coagulate and thus avoid rendering the water in the stream unfit for domestic water supply purposes.

(3) Notwithstanding the provisions of Subdivision 2 of this section, any placer miner who is operating by dredging process and who desires to transport his dredger across a stream where the expense of construct- ing settling ponds in the stream itself would, in the opinion of the oper- ator, be unduly heavy, shall have the right to conduct the dredger across the stream without constructing a settling pond under the following procedure : The operator shall give to the clerk or secretary, as the case may be, of each city or district owning or operating a domestic water supply the clarity of which is likely to be affected by the crossing opera- tion, notice of the intent of the operator to cross the stream. Such notice shall be given at least seven days in advance of the date that the operator expects to cross the stream with his dredger. Upon the expiration of

I'I.\( i;i{ MIMNd COM) IX ( AMIOHMA [Jillll. 1 :").')

the IK. lice ll |M'i-;it<.i- iiuiy duiiii:- I lie lollowiii' 4S hours coiKhic-t liis

(Ircdjii'r JiiTi'ss tlic str<'iiiii cvt'u tlioiili some turbidity nun' be caused llif crossiiiii' opfijil ion. llaviipj- crossed the sti'eam the operator shall Ihcrcupou aucl threat'tei" iu its lurllicr operations ()l)serve the proxisious of Subdivision "2 of this section.

Si;c. :;. Any person, fii-ni or corporation wlio fails to record the notice provided for in Section 1. or lo install the protective devices or to iive the notice provided I'or in Sed ion 2. or both, shall be jruilty of a nnsdenieanor. The operation of an.\- pla<M'r mine on <xr<tuml not covered by a pei-nnt to the operatoi- from the California ]3e])ris Commission, without compliance with the ])i-ovisions of both Sections ] and 2 lier(>of, is liere])y declared lo be a public nuisance which may be enjoined upon suit brought b.\- the dist rict attorne\ of the county in which the o])eration has been conducled. or by an.\- cil\ or district Avliose domestic water supply is rendered unlit or daniicrons foi- human consumption by the iu:\s, or failure to act, of the operator. The su]ie)"ior court of the county in liicli the opci-at ion is conducted shall have jurisdiction to hear and deter- mine the action and to awai-d such relief as may be proper therein. Xothin;:- in this act contained, however, shall be deemed or construed to deprive the State, any city, city and county, county, district, person, firm or corporation of any i-ijiht to brinji' and maintain any action or jiroceed- in-. in any jurisdiction, wliicli it was entitled to briuf; or maintain prior to the enactment of this act, or to receive or obtain in any such action any remedy accoi-ded to it under existin*;' law.

Si:c. 4. If iiuy section, subsection, sentence, clause or phrase of this iu;t is for any reason lield to be unconstitutional, such decision shall }iot affect the validity of the remaining;' portions of this act. The Legislature hereby declares that it would have passed this act and each section, sub- section, .sentence, clause and pln-ase thereof, irrespective of the fact that any one or moi'e sections, sul)sectious, sentences, clauses or phrases be declared unconstitutional.

(Added by Ch.rilo, Stats. 1!)41.)

Placer Mining Districts

Sections 2401 to 2.")12 of the Public Resources Code, i)rovide detailed procedure for the formation of placer mininii" districts. To a j?eneral idea of the pur|)ose, the first two .sections are quoted below :

"2401. Districts iiiiiy lio forinod in tiio nianiuT provided by this chnploi' for the imipnse of iiffordiii' faciiitii's for roiiductiiif; pinci'i- iniiiin}; without iii.juiy to ju-opprty iinl Kwiii'd by or inrludcd in the district.

"'2W2. rn.ccc.lnius (,<y I lie lunii.M i.m of :i pJ.iciT iniiiiiif; district sh:ill he coni-

I icc<l iiy pctilioii :i(l(ircsscd to iiiid filed with the jjoju'd of siipervi.sors of the poiiiity

in whi-h is iocjited the l:M;;est itroportioii in value of the lands within tlie proposed district .is shown liy the last e(nialized county assessment roll. The jietition shall he signed by twenty-five per cent of the owners of paieels of land sniijcct to assessment for distiict purposes."

As other sections mentioned above are availabh' in the Public IJesotirces Co(h> of California i)ublished both by Supervisor of Docu- ments, 214 State Capitol, Sacramento 14, aiul by Dancroft-Whitne}' Com- lun\'. 2(1(1 McAllister Street, San I'raiu-isco 2, they are not repeated liere.

Index

Aalders, II. J., and Prather, W. W., mining operations in I'lacer County, 271 Adams mine, I'lacer County, 273

property, Mariposa County, 261 Adits, in drift mininpr. SI, S2, S3 Aerial photo, sliowinp dredged strip of Yul)a Uiver, luO

photograpliv. ail to eeoloeic study, 153, Ifil, lO.j, 206 Aetna ohannel, Calaveras County, 237, 23S, 239, 240 Age of jjlacers, peologic criteria which determine, 1S3-1S6 Agua Fria Creek, Marii)osa County, 202 Ahart Ranch. I'lacer County. 276 Ainlay centrifugal gold savers, 49 Airola-Costa property, Calaveras County, 2.'j3 Alanta Mines. Inc.. oi)erations in Placer County, 276 Alaska, deep secular weathering in, 174 ; beach placers, diagrammatic cross-section of,

Albiez property. Trinity County, 305 Albright claim, I'lacer County, 27 4 Alex Perie proi>erty, San Joaquin County, 282 Allen, Victor T., quoted, 170 Allen property, Siskiyou County, 294, 298

Ranch, Amador County, 231 Allsman, P. T., cited, 48, 49

Alpha Stores dredging property, Nevada County, 209 Amador County, placer mines in, 231-233

Dredging Company. Amador County, 231 Amalgam, handling in sampling placer deposits, 222, 223 ; methods of cleaning, 13 4, ]3j ; methods of treating, 45, 75, SO, 135, 130

barrel, in black sand treatment, 79, 133, 134; in Denver trommel-jig unit, 31; in dragline dredge cleanups, 45 ; in treating concentrates, 65, 133

retort, drawing showing, 13S Amalgamating plates, use on fine material, 131 Amalgamation, in jigging, 09; in gold pan, 132; in sluice-boxes, 133; of concentrates,

131, 132; process explained. 129 Amalgamator, Berdan pan type, 134 ; clean-up pan type, 133; concrete mixer useil as. 134 : material requiring use of, 133 ; Titan, 74, 70 ; mechanical type, special use of, 133 ; used with jigs, 56 American Hill, Nevada County, 263

River, placer mining along, 2S1 : Middle Fork, placer mining on, 255, 250, 271 ; South Fork, placer mining on, 255

Rubber Manufacturing Company, cited, 59, 00 Amo mine. Butte County, 233

Ancient channels, 89, i55, 157 ; complexities of geologic history and structure, 161 ; methods of tracing, 175

river terraces, photo showing, 160 Anderson iiroperty. Placer C<iunty, 272 ; Stanislaus County, 304 .Angels ((uartz mine, Calaveras County, 237 Apron, in rockers, 23, 26 Arbuckle P.rfis., operations in Trinity County, 305

mine. Trinity County, 305 Arkansas mine. Nevada County, 269

Arlington and Osterman properties, Calaveras County, 252 Arrastre. photo showing use of, 14

Arroyo Seco Cold Dredging Company. .Amador County, 231 Arundel Corporation, operations in Yuba County, 315 Atkins mine, Nevada County, 209 Auburn Ravine. Placer County, 2 72 Averill, C. V.. cited. 36, 258, 277, 283, 28.",. 287, 2s9, 294, 300, 303, 305, 307, 309, 310 311

312, 313 A>ers, "William, property, Placer County, 272

B

B. H. K. Mines, operations in Shasta County, 283 ; operations in Trinity County, 305

Bacon, E. A., mining operations in Calaveras County, 251

Badger Hill property. Nevada County, 263 ; photo showing, 207

Bahr Ranch, Placer County, 272

Rajada, diagram showing formation in San Joaciuin A'alley, 198; placers, 152, 161, 160,

107, 198, 200, 207 Baker and McCowan. operations in Butte County, 233 ; operations in Plumas Countv, 277

Ranch, Placer County, 272 Bald Hill. Calaveras County, 236

Mountain channel, 291

338 PLACER MINING FOB OOLD IN CALIFORNIA |BulI. 135

Ball mill, for treating jig concentrates, 69, 76 ; rib-cone, used in black-sand treatment,

79, 80 Barges, pontoon, 39 ; used in dragline operations, 38, 39, 41, 42 Barker Corporation, operations in El Dorado County, 255 ; operations in Mariposa

County. 281 ; operations in Tuolumne County. 313 Barrows, diagrams by, 196

Batea, description of, 21-22 ; drawing showing, 22 Batbam, O. K., operations in Trinity County, 305 Batten properly, Calaveras County, 253 Bazet Estate property, Trinity County, 305

Beach placers, diagrammatic cross-section of Alaskan, 169; geologic explanation of, 1C8-170; Pleistocene and Recent, 205, 207

sands, photo showing mining of, 78, 168 Bear Kiver, Placer County, 277

Beaver Dredging Company, operations in Siskiyou County, 293 Becker, G. E.. inventcjr of single-bucket dredge, 61

-Hopkins single-bucket dredge, description of, 61-62; photo showing, 61, 62 Bedrock, concentration of gold on, 181, 183 ; release of gold from, 163, 174, 175 ; sluice grades determined by, 120

Tunnel placer mine, Nevada County, 263 Beds, for support of rockers, 23 Belkriet property, Butte County, 235 Bellota district, placer mining in, 283 Belt conveyor, on dragline washing plant, 3 8, 4 3 Bendelari jigs, on gold dredges, 6G ; tested in New Guinea, 63 Bent Company, mining operations in Fresno County, 257 Berg, H. A., mining operations in Madera County, 261 Berkey, Charles P., cited, 179

Best, C. L., photo showing gold nuggets from collection of, 290 Beverly, Burt, photo by, 154

Bibliography, of California placers and related subjects, 208-216 Big Blue Lead, at Mayflower mine. Placer County, 274

Canyon Dredging Company, operations in El Dorado County, 255

Dipper claim, Placer County, 274

Ravine, Yuba County, 315 Biggs Ranch, Sacramento County, 281 Bilkli property, Butte County, 235 Birchville, Nevada County, 263 Birds Eye Canyon mine, Nevada County, 269 Bishop Company, Thomas B., ownershijj of Vallecito-Western mine, 24 8

property, Calaveras County, 253 Black sand, accumulation in riffles, 64; accumulation in rockers, 23; constituents of, 175; economic possibilities of, 169; nature of California occurrences, 77; separation of gold from. 77, 79, 133. 134; separation of platinum from, 77, 79, 133; small-scale mining of, 79; treatment of, 77-80; treatment in amalgam barrels, 133, 134; treatment of amalgam from, 80; valuable mineral content of, 77

-sand load, in jigging operations, 74 Blackwelder, p:iiot, cited, IGS; diagrams by, 196; quoted, 165, 166, 193, 194, 200 Bloody Run Creek, Nevada County, 263, 267 Blowing process in treatment of concentrates, 132 Blue Canyon, I'lacer County. 273 ; formation. 292 : slate, 292 Bodinson Manufacturing Company, drawing by. pi. 1 ; photos bv. 30. 38, 40, 46

sampling machines, 31 ; photo of, 30

washing plant, 39, 41 Boe, B., cited, 108 Boericke, William F., cited, 21 Booming, in sluice-box operation, 128

Bottoms, P. H.. mining operations in Merced Countv 262 Boulders, methods of handling, 41, 61, 85, SS, 113. 114, 128, 222; photo showing forking

along sluice. 116 ; photo showing handling with derrick. 114 Bowie. A. J., cited, 98. 118, 120. 121. 123. 128. 130 Bowling Green property. Calaveras County, 253 Bradley, Walter W., cited. 145. 260. 263 ; photo by, 164 Brady, M. A., property in Trinity County, 307 Bragdon conglomerate, as source of gold. 36 Bramming, V. E., cited, 71 Brasswlre Gulch, Siskiyou County, 300 Breasting, definition of, 81 ; description of methods used in drift mining, 82, 86. 88,

Brennan. J. P., operations In Shasta County, 283 ; operations in Trinity County. 305 Brooks, Alfred H., cited, 161 ; quoted. 174. 175, 178 Brown, M. K., property, Trinity County, 305

Bros, mine, Nevada Countv, 269 Browne, Ross E., cited, 271 Browns Creek, Trinity County, 305

Hill mine, Nevada County, 269. 270 Brushy Slide mine. Placer County. 273 Buck't-elevator use in black-sand treatment. 79 ; use in small-scale placer mining, 34

- adder dredge, comparison with dragline dredge, 34, 35 ; portable 34

-line dredge, cost of, .'il; description of bucket, 57. 58; photo showing, 54; photo showing latest bucket design. 56 ; photo showing repairing of, 56

-line dredgmg, description of. 51-60 ; effect on land surface, 52

Bucyrus-lOrie drasline excavator, ."i"

lUilfards l!ar (lam, Sierra County, 285

lUilldozer, used witli draRline dredge, lif), 38 , .„ , .1 10

HuUion, gold-, im-tli()<l of molding, HO; sampling methods, 140, 141, 142

mold, drawing sliowing, 138 nulolo Cold Dredging Company, jigging tests mad.- l)y, (13

goldfields, use of I'an-Amerii-an jigs, (iii Burns Creek, Mariposa County, 2t;i

J?urson Mining Company, <,prrat ions in (alavtias County 2..! Uutte County, placer mines in, 233-23r, ; singl.-hm ket dredge operations in, G2

Operating Company, operations in lUitte County, 233 nyers property, Calaveras County, 2r)3 Dyrne claim. Placer County, 274-27")

C. & E. Dredging Company, opeiations in Siskiyou County, 2!)3 ; operations m Stanislaus

County, 304 Cady Ranch, San Joa(|uin County, 2.S:',

Cal Oro Dredging Company, oiieialions in Siskixou County, 293 Calaveras Cement Company i)roiierty, Calaveras County, 253

Central mine, Calaveras County, 23r)-247: eliaracter of production, 242-243; costs, 241-242 ; development, 2:!S-2:i'J ; drag scraping in, 245-240. ; drifting opera- tions, Nl ; gravels and channels of, 2:'.C-237 ; history and iiroduction, 230 ; mining and milling, 24i-241 ; project for improvements, 24()-247 ; reserves and values of gravel, 2311-240; table of mining and milling costs, 241; table showing daily production, 242 ; technology of drift mining in, 243-245 Central shaft, sequence of strata in, 238 County, drift mining in, 247-251 ; jilacer mines in, 235-254; Tertiary Central Hill

channel, i>hoto showing, 151 Gold Dredging Company, operations in Nevada County, 2G3 skull, 23G California Debris Commission, 203, 270, 273, 325-333 ; see also Caminctti Act

Gold Dredging Companv, oiierations in San Joatpiin County, 282 ; operations in

Stanislaus County, 304 T-iands, Inc., placer mining on laoperty of, 282 placers, bibliography of, 20S-21(; Calkins property, Siskiyou County, 297-298 Calmo Mining and Milling Companv, Calaveras Cf)untv, 23(;, 239

shaft, 239 Camanche district, placer mining in, 253, 282 Caminetti Act, 2G3, 325-333; affecting debris dams, 144; amendments to, 331-333;

cited, 159: see also Cdlilornia Drhris Commission Canipo Seco district, mining operations in, 253 Canepa property, Calaveras County, 253 Canyon Creek, Placer County, 276

placers. Trinity County, 305 Capital Dredging Company, operations in Sacramento County, 280 Carboniferous, Bragdon conglomerate, 3G

Carmichael Irrigation District, suit against Lost Camp Mining Companv, 273 Carrville Gold Company, l)ucket-line dredge of, 55 ; operations in Trinity County, 305 ;

photo showing bucket-line dredge of, 54 Carson Creek, El Dorado County, 25G

Dredging Company, operations in Sacramento County, 280-281 Cassaurang Ranch, Madera County, 2G1 Cassiterite, tools for, separation of, 21 Casteca Canyon, Los Angeles County, 2G0 Cat Camp mine, Calaveras County, 251 Cateri)illar equipment, 34, 37, 38

Central Bank of Calaveras, placer mining on projurty of. 282 distributing system for jigs, G8 Hill channel, at Calaveras Central mine, 23G, 237, 238, 239, 240; at Vallecito

Western mine, 248 placer mine, Nevada County. 2GG-2G7 Challenge claim. Sierra County, 287

district, placer mining in, 315 Champion Flat, Nevada County, 263

Gulch. Shasta County, 283 Chaney, Ralph W., quoted, 184, 185 Chapman, T. G., cited, 131 Chase Ranch, Mariposa County, 262 Cheney Creek, Humboldt County, 25 8 Cherry Creek, Siskiyou County, 293 Chicken Point mine, Nevada County, 269 Chico formation, placer reserves in, 152 Chili Gulch Blue Lead channel, at Deep Lead placer mine, 252

Deep Blue Lead channel, at What Cheer mine, 254 China Gulch, Shasta County, 284

Chittenden. C. N., mining operations in Placer County, 271 Chocolate Mountains, water courses from, 259 Christian property. El Dorado County, 257 Church Union mine, Calaveras County, 252

:{4() ri.Ac i;k MixiNii lou (;<i,i) calu'ornma |Ru11. l:i.")

Cinco Mineros Company, operations in Trinity County, 305

Cinnabar, tools for separation of, 21

City-of-Slx channel, 291

Clark, \V., mining operations In Calaveras County, 2.)2

property, Hutte County. 235

-Jansen pmperty, Trinity County, 309 Cleaner jip, treatment of concentrates from, 69, 70

Cleanup-pan, use as amalgamator, 133 .

Cleanups, in hydraulic mining, 115, 119, 128; in jiRRing, 71, 74; in placer niming. 128, 129: in platinum-metals separation from gold, 139; in small-scale placer mining. 23, 29 Clear Creek, Shasta Count\ , 283, 284 ; jilacer deposits on, 36 ; Dredging Company, opera- tions in Shasta County, 283 Clerkin property, Nevada County, 263

Climax Dredging Company, operations in Sacramento County, 281

Coast Ranges, geology compared with that of Sierra and Klamath regions, 206 ; Ter- tiary and Cretaeeous deposition in, 206 Coffee-Mill channel, at Church Union mine, 252 Coleburn pro])erty, Nevada C:'ounty, 266 Collins, F. \V., cited, 71 ; ?,'otrs on jigs for r/old dredges, 73-76

property. Siskiyou County. 298 Coloma Creek. El Dorado County, 255 Columbia Construction Company, operations in Shasta County, 283

Hill, Nevada County, 265 Combie Reservoir, Nevada County, 270 Comet claim. Sierra County, 287 Concentrates, cleanup in rougher-jig operation, 74 : blowing process in treatment of,

132 ; rocking in treatment of, 132 ; separation of gold from, 131-135 Concentrating pans, in Denver mechanical gold pan, 31 Connelly, R. C, property, Shasta County, 283 Consolidated placer mine, Nevada County, 266-267 Contouring of ancient surfaces, usefulness of, 154-155 Copper plate, amalgamated, use in gold recovery, 23 Corbett Creek, Mariposa County. 262 Corley property, Yuba Cf>unty, 315 Cory and Strong placer, Hutte County, 233 Cosumnes Gold Dredging Company, operations in Sacramento County, 281

River, Middle Fork, placer mining on, 2rir) ; North Fork, placer mining on, 256; district, jilacer mining in, 2S1 Cottonwood Creek, Shasta County, 284 Coyote Creek, Calaveras County, 253 Craig Osborne property. El Dorado County, 256

Royce property. El Dorado County, 256

Salt Water property, El Dorado County, 256 Cranes, draglines used as, 34, 35 Cratt property, Butte County, 235 Cretaceous, Lower, marine sediments of, 170

conglomerate, as source of gold. 36

erosion of gold provinces of California, 201

placers, 170, 186, 206, 208

sediments, as bedrock for dragline operations, 36

Sierra Nevada topography, block diagram illustrating, 109 Crews property. Trinity County, 305

Crocker-IJuffman Iand and Water Company property, i)lacer mining on, 261, 262 Crosscut, defined, 85, 86 : breasting in connection with, 87 Crow Creek, Shasta County, 283 ; Trinity County, 308

Dredging C<imr>any, operations in Shasta County, 283-2S4 Crowder and I'.inney proi)erty, Rutte County, 235 f'rucible, drawing sliowinft, 138 Cutter and Mueller, operations in Sacramento County, 281

Dakin Company, mining operations in Nevada County, 263 Daly Gulch, Shasta County, 284 Dams, diversion, in hydraulic mining, 99 Darby property, Rutte County. 235

and Crowder property. Rutte County. 235 Dardanelles mine. Placer County, 273 Daultin. T. M.. cited. 113 Davidson, George, cited, 171 Davis, H. W., cited, 139, 140

Davis, William Morris, cited, 197; diagrams by, 172 Day, D. T.. cited, 77, 169 Deadwood district, placer mining in, 293

Debris dams, coiulitions making constructif>n necessary, 144 ; locations of, 145 Deep Blue Lead channel, at Hook and Ladder mine. 256

Lead placer mine, Calaveras County, 252, 254 Deer Creek, El Dorado County, 255 Deflectors, table showing weights and prices, 106 DeKarr and Herbert, operations in Shasta County, 284

ixDKx ;ui

Del Norte County beach sands, platinum recovery from, f.„-mnti..n l.v streinT;

Delta drawings showing vertical- and cross-sections of, 1S2, foimation, 1)> sticams,

179, 191 : formation, diagram showing, 19S Dennis district, placer mining in, 261 . . , o-. . ,. n,,., ,„.,,.i,inf> marif-

Denver Equipment Company, drawing hy, 32; photo by, 3... sampling in<u innos maoe

mechank-aV gold pan, description of, 31; drawing showing parts of, 32; photo

showing, 33 trommel-jig unit, description of, 31-33 Depleted placers, geologic classification of, l.')l Deposition, stream, 1.".3, ir.4, ITS, 17!t, ISI

Depot Hill hydraulic mine, Siena County, 2S:, ; photo of. 2S.)

Derrick, handling boulders with, IH : photo sliowing, 114 . .-o ,

Desert placers, ir.3, l(;i. Did. KiT, liiS. 197. 200, 207; reserves m, 1..2; see also hujadd placers and dr\i processes, in placer formation, 197, U'OO streams, erosion by, lit", 2(i0 Ditert Kstate, Amador County, 2:!1 1 >iikerson property. Trinity County, 301) Di<-khaut Ilanch, Calaveras County. 2:.3

Dip-box, '1\; description of, 27-2S ; iihoto showing use of, 27, 7S Disillusionment, in small-scale placer mining, 13. 1."), IS, 19 ...

Ditclies, 94-9S, 99, 112 ; construction designs recommended. 9. ; sluiiing m. li'.i ; spill- ways on. 97 ; table sliowing side slopes recommend. d toi-, '.i7 ; table shownifi velocities in. 95 TMtchlines. for hydraulic mining, 99 ]>iversion dams, spillways on, 9I Dobbin Gulch Dredging Company, operaticjns in Shasta County, 2S4 ; operations in

Trinity County. 307 Dondero mine. Tuolunuie County, 313, 315 l-lonnelly, Maurice, cited. 157

and Johnson property. Nevada County. 2GC Doodle bug, dragline dredge, 3 4 Douglas, Jack, cited, 21

Jacob property, Butte Ci>unty, L'35 Dove Mining Company, operations in Yuba Cnmty, 315 Drag scrapers, used in Calaveras Central mine, 2)5-2_4f;

Dragline dredges, capital investment re(iuired in T.i3:i, 4n: (.Icunui's, 45: crews. 45, 4*;: definition of, :!4: delays in f>perating. 45; disad\ antagcs of. :15 ; <liawiiig showing cross-section of riffles. 43 ; drawing showing jilan view (f. i>I. 1 j drawing showing side elevation of. pi. 1 ; moving costs. 45 ; oi)eiating costs in 1937. 4f>-4S; photo showing. 3S. 42, 44. If,. 54; iihot.> showing hand- wincii. 39 : photo showing iviwer-winch, 40 ; ])lioto sliowing tiomnul. 40 : table showing gr)ld ])rodu<tion. 1933-43, 35; used as cranes, :;4. 45; used in black-sand treatment, 79 dredging, descrijition of, 34-4S excavators, as digging unit in dragline dredging. 34 ; desciiption of. :'.7 ; nicthoils

of digging with. 37 ; used with dry-land di-e<lges. 4;t machine replacement. 3 4 Drainage jiattern, drawing showing de\eloi)ment of. 19S Dredge construction, future, 00

hulls, constru<-tion with portable ixmlooiis, 59 tailing, testing of. f.G. 07 -tyi)e riffles, drawing showing. 122 Dredges, drawing showing jig installations on. 70; drv-laiid. (bsniiition of. 411-50: factors affecting jig installation on, 07-OS ; op.ialing c.sts for niod.Tu typos, 52 Dredged strip abnig Yuba Uiver. aerial photo showing, 150 Di-odging, bucket-line, desci-iption of, 51-00; conditions in f'alifornia 0(i dragliiU'

description of, :!1-4S; -land, the forming of, 5:; Drift, defined, 85, SO

mining, at Calaveras Central mine, 243-L'45; breasting method.s de.scribed, S7, SS, 90, 91 ; e<|uipment for, S3, S9 ; explaiuxtion of term, SI ; factors affe<-fing, 89, *tO; influen<e of ancient channels f>n. S'J ; influence of economic con- ditions on, S!t : methods des<ribed, S1-!I2 ; nature of deposits suited to. SI ; o|>erating expense, early-day and lec.-nl compared, S!t. 90, 91 : I'lacer County, 157; specially designed machines for, ;i] ; .spiling in connection with. 85, 80, 87 l>rifting, breasting in conneetion with. S7 ; cost of. S(;. ST; nietliod and cost of small

operations. 220 Drilling, as method of sampling phoer diposits. 222-220, 227 Drinkwater, J. C. cited, 144

Drive-pipe sampling, preparatory to (hedging. 222 Dry Creek. I'lacer County. 272 ; placer deposits on. 3i; -land dredge. oi)erating cost. 4 !t ; photo showing. 50 -land dredging, description of, 49-50

placers, 153, 101, 160. 107, 197, 198, 200. 207: effect of wind and sheet floods on 167, 168: need of geophysical surveying. 157 : see also 'la phncru and desert placers Duffy property. Kl Dorado County. 255 ; Placer County. 271-272 Dunn. R. I cited. 170 Durvea mine. Nevada County. 2<)9 l>utch Flat, riacer County. 271, 272, 270, 277

342 rr,A(F.R mixin-c; for gold in California [Bull. 135

East Belt district, placer mining in, 313

Weaver Creek, Trinity County, 313 Eastman Gulch, Trinity County, 307 Eddy, H. P., cited, 96 Edman, J. A., cited, 169

Education, facilities available to small-scale placer miners, 18 Egleston, Thomas, cited, 98

Eimco-Finlay loaders, used in Calaveras Central mine, 24 4, 245 El Dorado County, eluvial placers in, 163; placer mines in, 255-257

Creek, placer mining on, 261

Dredging Corporation, operations in El Dorado County, 255 El Oro Dredging Company, operaticjus in Placer County, 272 Elder property, Nevada County, 2 OS

Electric power, large expense in bucket-line dredging, 52 Elephant hydraulic mine, Amador County, 231 Elevator, hydraulic, 106, 107, 108; drawing showing. 111

Ruble, drawing showing, 108 ; for use in hydraulicking, 106 ; i)hoto sliowing, 110

step-lift, used in hydraulicking, 107 Eliel, Leon T., cited, 153 Ellsworth, E. W., cited, 227 Eluvial placers, geologic explanation of, 103 Emigrant mine, Nevada County, 20 ft Emma mine, Butte County, 233

Gordon property. El Dorado County, 257 Engineering and Mining Journal, photos supplied by, 150, 160, 204 ; reprint from, 317-322 English, Walter A., cited, 153 Eocene beach-placers, 170

channels, 263, 266, 276, 287 ; gold values in, 170, 175, 208

structural control of gold provinces, 201 Eolian placers, geologic explanation of, 167, 168

Erosion, Cretaceous, of gold provinces of California, 201 ; cycle of, 194 ; effect on gold concentration, 181; of bajada placers, 160; of lakes in Sierra Nevada, 205; of residual placer, 163: of streams, 165, 171, 178, 186, 187. ISS, ISU, 194, 197 ; on river bend, diagram showing, 177 Esco bucket, for dragline dredging, 37 Esperance mine. Nevada County, 263, 264, 205

Etna Gold Dredging Company, operations in Siskiyou County, 293 Excavators, draglines used as, 34

dragline, discription of, 37 Excelsior mine. Placer County, 273, 274 Exploration methods, significance of improved, 152-154 Explorers, Inc., property. El Dorado County, 255 ; Mariposa County, 261

Fair Oaks, Sacramento County, 282 ; Gravel Company, operations in Sacramento

County, 282 Fairbanks, H. W., cited, 157

Fairchild Aerial Surveys, Inc., map furnished by, 202 Fancelli property. Trinity County, 309 Farnsworth mine. Siskiyou County, 293 Fassett-Parker-Hanlon property, Sacramento County, 2S1 Fault blocks, drawing showing down-dropped and uplifted. 172

zones, map showing major California. 158 Faults, gold deposits in, 173, 204, 205, 207 Feather River, placer reserves, 152 Ferrari property. Placer County. 276 Ferreva Ranch, Placer County, 276 Filibuster Flat, Trinity County, 313 Finch, R. H., cited, 193

First Chance property, Yuba County, 315 Fish and Game Code, extracts from, 33 4, 335

Ranch, Shasta County, 284 Fisher and Baumhoff, cited, 63, 71

property. Calaveras County, 253

ranch, Placer Countv, 275 Flat Creek. Shasta County. 284 Flint, R. F.. quoted, 187, 191, 193 Flotation, for fine-gold recovery, 65 Flow-sheet for use of jigs, 75

Flumes, cost and method of constructing wooden, 99 ; photo showing construction of, 92 ; .safety measures In connection with. 99 ; use in hydraulic mining, 98 ; use with long toins. 28 ; working auriferous gravels in, 29 Folsom district, placer mining in, 278, 281 Forest, Sierra County, 291

Hill Divide, drift mines of the, 271

Service, regulations for placering, 20-21 Forestblll. Placer County. 271. 273. 276 Forschler Ranch, Shasta County, 284

Index 348

Forsyth and Lewis property, Placer County, 275-276

Fossils, significance of, 184, 188

Foster Ranch, San Joaquin County, 282

Francis formula, for calculating water flow, 98

Franke. H., cited. 235

Fraser and Alexander property, Nevada County, 263

Freidel property, Butte County, 235

French Corral placer mine, Nevada County, 263-265

(.Julch, Shasta County, 284 ; district, source of Clear Creek placers, 36 ; Dredging Company, operations in Shasta County, 284 Fresno County, placer mines in, 257-258

River, placer mining on, 261 Fretz, property, Mariposa County, 262 Friant dam, Fresno County, 257 Froloff property. Trinity County, 309 Fulda Creek, I'lacer County, 273

t;-B portable placer machine, description of, 33 <Jail placer mine, Nevada County, 209 Gallia mine, Siskiyou County, 293-294

Placer Mining Company, The, operations in Siskiyou County, 293-294 (Jamble, V., property, Butte County, 235 Gardner, E. D., cited, 48. 49, 81, 83, 93, 131, 175, 219, 221, 225, 226, 268, 285, 293,

294, 298, 310, 311 Garibaldi mine, Amador County, 231 Garland Mill Slope mine. Placer County, 273, 27 4 Gas Point, geology in vicinity of, 36 Gaskill property, Mariposa County, 262 (Jasper property. Trinity County, 313 Gaylord, H. M., cited, 229, 258 : quoted, 35

Gem stones, jigs used in recovery of, 63 ; tools for separation of, 21 General Dredge property, Siskiyou County, 298

Dredging Corporation, operations in EI Dorado County, 255 ; operations in Sacra- mento County, 281 (lenetic types of placers, 161 (Jenochio pro)>erty, Calaveras County, 252 Cicologic age of placers, 183-186 classifications of placers, 150

conditions in gold provinces of California, 200-201, 204-206 map showing prevolcanic topography, 156 Geology of placer deposits, 150-216 : bibliography, 208-210 Geomorphology. 153 : see also physiograpliy Geophysical prospecting methods, 227

surveying, 153, 161 ; as aid to geologic study, 206 Germain, A. G., operations in Stanislaus County, 304

Giants, number and size in use in 1932, 113 ; photo showing, 104 ; photo showing stack- ing of tailings with, 117 ; table showing flow of water through, 107 : table showing sizes, weights, and prices, 106; use in hydraulicking, 94, 99, 105-100, 112, 113 Gibson, M. K., Mining Company, operations in Nevada County, 265 flilbert, F. C, quoted, 188, 189

G. K., cited, 119, 187; diagrams by, ISO, 1S2 ; quoted, 189, 190, 191 Gill, Corrington, cited, 13 (Jivens property, Mariposa County, 261 (Jlacial placer deposits, 161, 165. 166. 193, 194 Gladding Ranch, Placer County, 271 Glo-Bar Mines, operations in Calaveras County, 252

flold, accumulation in rockers, 23, 26; amalgamation with quicksilver, 31, 42, 135, 136; amalgamation in sluice-boxes, 133; balances for weighing, 141, 142; extraction from amalgam, 135-137 ; in beach sands, economic importance of, 169 ; in dredging areas, nature of, 53 ; in placer samplings, method of calculating, 223; in placers, geologic explanation of origin of, 173-174; marketing of, 142-143; melting process for marketing, 140; method of shipping, 142, 143 ; release from bedrock, 174, 175 ; separation of platinum- group metals from. 137-140; separation from black sand, 77. 79, 133; separation from concentrates, 131-135 ; table showing California produc- tion, 1848-1944, 16-17; table showing production from dragline dredging, 1933-43, 35 ; transportation, deposition, retention in str ms, 178-181 Acres mine, Shasta County, 285 Bluff district, placer mining in, 258 bullion, molding process, 140 Delta placer mines. Imperial County, 259

dredging, attempts in California, 51 ; jigging applied to, 63-76 ; principle of, 53 Hill Dredging Company, operations in Butte County, 233 ; operations in Calaveras

County, 252 : operations in San Joaquin County, 282 nuggets, formation of, 179 pan, description of, 21-22, 133; drawing showing, 32; mechanical, 31-33; use of

amalgamation, 132 ; use in sampling natural exposures, 220 Placers, Inc., operations in Placer County, 272 price increase, effect on small-scale placer mining, 14

344 IM.AI KK AIIMNC lOK COM) IN ( AI.IFOKNIA |liull. IM.")

Gold — Continued „„ „„„

provinces, geologic conditions in California, 200-201, 204-206

-quartz veins, erosion of, 36

Recoveries Corporation, operations in Placer County, 272

recovery, photo showing primitive methods, 14 ; undercurrent method or, 127, 128

Reserve" Act of 1934, cited, 140

Run, riacer County, 271. 276

-saving, by riffles, theorv of, 121 ; table arrangement, 57

Valley Dredging Company, operations in San Joaquin County, 282 Golden Belt Mining Company, cost of running drift for, 86, 87

Feather Dredging Company, operations in Butte County, 233-234

Gravels Mining Comi)any, operations in Trinity County, 307

River Mining C(imi)any, operations in Calaveras County, 252 Goldtleld Consolidati-d Mines Company, operations in Trinity County, 307, 311; photo

showing hydraulic mine, 306 Good Luck mine. El Dortulo County, 255 Gould, James L., property in Placer County, 277 Grant Pacific Rock Company property, Fresno County, 258

-Service Rock Company, operations in Fresno County, 257 Gray Lead channel, at Hook and Ladder mine. 255-256 Great Basin region, bajarta placers in, 167, 207 ; Pleistocene faults in, 171, 173, 204, 207

Valley, placer deposits in, 205, 206 Green Spring mine, I'lacer County, 273 Greenhorn Creek. Nevada County, 269

district, placer mining in, 293, 298

Dredging Company, operations in Kl Dorado County, 255

mine, Nevada County, 269 Greenwood Creek, El Dorado County, 255 (Gregory Ranch, Calaveras County, 253-254 Griffith Company, mining operations in Fresno County, 257

Grizzly, as feeder to undercurrent, 30 ; as part of Ruble elevator, 106 ; function in drag- line dredging, 41 ; function in hydraulic mining, 115, 127 ; function in sluicing, 2!"

Canyon, Nevada County, 267 Gruwell, C. E., mining operations in Calaveras County, 252 ; operations in San Joaquin

County, 283 : operations in Shasta County, 284 Guttinger, Albert, properly, Calaveras County, 253

John, property, Calaveras County, 253

Ilageman property, Calaveras County, 253

-Huberty i)roperty, Calaveras County, 253 Haley, C. S., cited, 144. 159

Hall and French, operations in Nevada County, 265 llallstrom and Lindblad, mining operations in Placer County, 2 72 Ilalt.r mine, Calaveras County, 254

Jlammon Engineering Company, work at Hook and Ladder mine. 256 Hammond, John Hays, cited, 242, 273 Hand methods, in small-scale placer mining, 19

-winch, for dragline dredge, photo showing, 39 Happy Camp Dredging Company, operations in Siskivou County, 294

Valley, Shasta County. 2S4 : Blue Lead, operations at, 254 ; Land and Water Com- pany. i)lacer mining on property of. 285 Ha(|uinius, E., cited. 153

Harms Bros, and Larsen Bros., o))erations in Siskiyou County, 294-297 Harrin, Mary, property. Butte County. 235 Harz jig. use in early jigging i)ractices. 66 Havilah Gravels. Inc., operations in Trinity County. 307 Hawkins Canvon, Neveda C<junty, 269 Hay, Oliver P., cited, 185 Hayfork, Trinity County, 305

district, placer mining in, 312 '

Hazelroth claim. Placer County. 274 H.izen. Allen, cited, 93

Helen Whittier property. Butte County, 235 Henry. J. H., mining operations in Calaveras County, 252 Henshaw, Paul C, cited. 259

Hiatt, Wm. P., Ranch, mining operations at, 253 Hidden Channel, Trinity County. 313 Higglnbotham property, Stanislaus County. 304 High Channel mine. Trinity County, 312 Hill. J. M., cited, SI ; quoted, l.;7 Hinds, Norman E. A., cited, 36, 157 Hodgkin, Emma J., prfipcrty. El Dorado County, 256 Hoefling Bros., operations in San Bernardino County, 282 Hogate R.anch, Calaveras County, 252 Holcomb Valley district, placer mining In, 282

Valley P',',,'.""'j,'i,'">'' "Perations in Kern County, 260; operations in Sacramento

Hook and Ladder niine. El Dorado County, 255-256 ; Trinity County, 305 Hoosier Gulch Placers, operations in Sacramento County 281 Hoover, H. C, cited, 161

i\i)i;x .'Uf)

inillf, I'hKci- Ciiunly. liTo

llDpkitis 11 11 iiiMiilur nf sitmlt'-bucket dreclRe, Gl

iin<l'l'<K.r. iiiitiitiK !'iati<.ii.s ill Kn-sii() Ooinity, .-,7 , ,oo.,.

llnppiT ill Dmv.r in.M'lianic;,! j;..l.i p:tn, :! 1 ; in ,lip-li..x, ; in diaKlinr iln-., ns, 41 ;

in C-i: portal. Ir pla.-.r inadiinc, :!:! lloniiaii claim, I'la-cr Cniinly. JTI. JT:. llnnu.r. U. K.. cil.d, Ki'.' Uursf Cri'oU, iilacrr niiiiin;; mi, I'lil-l'l'. lli.r.M-hi.f Bar, 101 Durad'i ('"unty, :;:.ii ; I r 'miiity, J i L ,. i

Dri-tlniiiK Company, oimrat ions in Ama.loi' ('Munly, J.; I ; op.iat s in ( alavfras

Connly, :;r.2 ; operations in lOl l>oi;olo oiiiit.\, ...h llorton. V. "SV., cited, 235, 24,S, 2GI

K. E., cited, HG

mine, Amador County, 231

Culch mine, Siskiyou County, 294 llotchkiss Suiierdip maKnetonieter, 227

Huelsdonk, ].. I.., A syiioiitic prcsunipt ion rtiionluuj Calil oniia'.s iiiiiks. s|i-;i1 ; photos by, 2S.S, 2Sit, 29"

concentrator, use in Calaveras Centra! mine, 211 Hughes property, VA Dorado County, 25.') Huliii, C. 1)., citid, 157, 107 Hulls, for bai-Kcs, constructif>n, 39; for Inicketline dredfes, iiortab!.' pontoon construe-

tion, 59 Ilumbfddt County, placer mines in, 25.S-25!t ; workin.t; of beaili sands, 7S, 79 IJumbuK' Cre.-k, Nevada County, 2ii7 ; Siskiyou County, .'.nu Hume and Coleman iirojierty, liutte County, 235 Humiihrey.s Cold Coriioralioii, dry-land dredKcs built by, 19; ojieialioiis in liulte

County, 234 ; operations in Sacramento Counl\, I'M Hungarian riffles, in bucket-line dredging, 5.;; in dragline dre(lK<- cleaning, 45; use in

Calaveras Central mine, 241 Hunt Ranch, Calaveras County, 253 Hunter Valley district, placer mining in, 2G1, 2G2 Hutchison i)roperty, Sacramento Count.v. 2S1 Hydraulic classifier, used for sizing black sands, 77

ditches, table showing velocities in, 95

elevator, lOi;, 107, lUS; drawing showing, 111

jig, 73, 74, 79 ; see also pulsator jig

mine, photo of flume for, 92 ; photo showing pipe installation, lUU

mining, application to placer methods, 9.",-ll(;; costs, :):; ; damage from, 144 ; detini- fion of, 333; early-day practices, H>S : eMUiiiment, 99; t.ipe-liiies for, 100-105 ; sampling in connection with, 22ii ; water supply lor, 93. 94

Igo, gravel deposits in vicinity of, :'.G

district, i)Iacer mining in, 283, 2,S4 Imperial County, placer mines in, 259-200 Independence fault, 202

gold mines, Amador County, 231 Indian Canyon, Placer County, 272

Creek, Kl Horado County, 25t; ; Siskivr.u Countv, 293

Hill mine. Sierra County, 2S5, 287

Springs mine, Hutte County, 233 Ingram, W. I)., mining o]ierations in Kl Dorado Countv, 25C ; mining oiierations in

Placer County, 272 Innis, A. B., operations in Nevada County, 205

]>redging Company, operations in Placer Countj-, 272; operations in Plumas County, 277 Interstate Mines, Inc., operations in Butte County, 234 ; oiierations in Trinitv County, 307 lone formation, 152, 170, 1S4, 20S ; defined, 170 Iowa Hill district, placer mining in, 272, 274 Irish claim. Placer County, 274, 275

Creek Mining Comjiaiiy, ojjerations in Kl Doratlo County, 250

Hill mine, Amailor County, 232 Irvine, K. S. J., cited, 144

.lackass property, Tuolumne County, 313

Jackson, T. H., cited, 144

Jamieson, T. G., drawing supplied by, 155

Jamison Creek, Plumas County, 277

Janin, Charles, cited, 130

Jarman, Arthur, cited, 144, 2G3, 2G8, 209

Jasper-Stacy Company, operations in Placer County, 272

Jenkins, Olaf P., Neic technique applicable to the study of placers, 150-208 ; Physio- graphic map of California, 158 ; cited, 185 ; quoted, 181, 183

Jenny Kind district, placer mining in, 253, 282, 283, 300, 304 Lucas property, San Joaquin Count>\ 282

Jig, as bucket-line dredge equipment, 53, 55 ; as gold dredging equipment, 03-70 ; central distributing system for, C8 ; in Denver trommel-jig unit, 31 ; tailing recovery by means of, 07 ; testing before installation, 07, 73 ; use of, compared with riffles, 03, 04 arrangements, drawing showing, 70

'14r. PLACKR MINIXfi FOR OOLD IN CAI.IFORN'IA [BuH. l-'M

Jig — Cotitlnuod

Hendelari. use on buckct-lii.e dredges, SS

cleaner-, treatment of concentrates from, 60, 7fi

Harz, used In early jlRRing, r>6

Installation, factors affecting, f.7, 68

Pan-American Pulsator, 73. 74, 79

placer, 5 .1. 63. 66

recovery factors affectinpr. 67, 68

rougher, 68, 69, 73, 74 : photo shf>wing 4-cell block, 74

scavenger, 68, 60, 73, 74

testing set, photo showing, 72

Yuba, fidaptations of, 55 Jigs, cleanuiis from, 71 : comparative use as essential and auxiliary equipment In dredging, 69, 71; development of operating methods since 1037, 73-76; factors affecting installation, 67, 68 ; factors affecting operation of, 67, 68 ; fU)W sheet for use of, 75 John Aim property, Rutte County, 235

Hilkli tiroperty, Hutte County, 235 Johnson, C. H., cited, 81, 93, 131, 175, 219, 225, 226, 268, 285, 203, 294, 298, 310, 311; diagrams by, 169, 192

Douglas cited, 194

K. W., Ranch, Calaveras County, 236

J. F., cited, 83

Itanch, TMacer County, 271

Walter W. Company, details of dredge construction furnished by, 300 Johnsville district, placer mining in, 277 .lones, J. Wesley, quoted, 52 Joshua Hendy Iron Works, cited, 105; table on flow of water through giants supplied

by, 107 Joubert mine, Siskiyou County, 29 4 Julilin, C. K., cited, 235, 248, 261 Junction City Mining Company, operations in Trinity County, 307-308; photo of

dredge, 306 Jupiter mines, Nevada County, 269 ; mine, Placer County, 274

Kaasa property, Stanislaus County, 304 Kalbaugh, C. L., operations in Trinity County, 308 Kaneko Ranch, Placer County, 276 Kaiilan mine, Tuolumne County, 313, 315 Kate Hayes property. Nevada County, 263, 265 Kates mine, El Dorado County, 257 Katesville Culch, Sacramento County, 281

Kaulfield and Danison, operations in Butte County, 234 ; operations in Nevada County,

and McKinley, operations in Nevada County, 265 ; operations in Placer County, 272 Kehoe property. Mariposa County, 261 Kenna mine. El Dorado County, 257 Kent, E. A., operations in Tuolumne County. 313

property. Amador County. 232 Kentucky Flat. F:1 Dorado County, 257 ; mine, 257

placer, workings at, 252 Kern County, placer mines in, 260 Kerr, W. C, cited, 175

Keystone drill, designs and distributors, 222, 223 Kiessling. R. T., cited, 13 King Solomon mine, photo showing. 164 Kipi). P'rank. property. 101 Dorado County. 256

Klamath Mountains, geology of placer deposits in. 152, 157. 159. 163. 173. 207; gold provinces in. 200-201. 204-206

River, placer mining on. 258, 294, 297, 300; district, placer mining in. 298. 300 Knights Ferry district, placer inining in. 304 Knopf. A., quoted. 187. 191, 193 Kr>ehrlng dragline excavator, 37 Kohle, Fred, property, Shasta County. 284 Kutter formula, for determining velocity in ditches, 95, 98

modification of Chezy formula, 103-105

I>a Bienvenlta mine, Tuolumne County, 313 fJrange district, placer mining in, 304

fJold Dredging Company, operations in Merced County, 262 ; operations in

Stanislaus County, 304 Placer Mines, Itd., operations in Trinity County, 308 property, 313 Kamp Pros., operations in Placer County, 272 I'orte channel, 2 87 dl.struct, 277 Taizure, C. McK., cited. 31. 79. 261 I..ake Spaulding. Nevada County. 266

Lakes, formation by landslide, sketch showing. 172; geologic relation to stream Chan- nels, 197, 200, 201, 205

Index 347

T.anchii Plana. Amador County, photo showing removal of overburden at. 286 d„.,„

J.ancn.i company, operations in Amador County 232 ; operations Butte

(Guilty. 2.34 ; operations in Calaveras County. 253 ; operations In Sacra- mento County, 281 w , no Landslide, sketch showing lake formation as result of, 17<J Lange property, Siskiyou County, 293 „. , . . on, om Larsen Bros. km\ Harms Bros., operations In Siskiyou County, 294-297 Lava flow, Tuolumne County, photo showing, lo4 Laws, affecting placer mining. 323-336 : regulating ore buyers, 143 Leahy vibrating screen, use in Calaveras Central mme, 241 Leak Ranch, I'lacer County, 272 Leal property, Butte County, 235

Lebanon Consolidated Mines, operations m Placer County, -i Lee, C. I-'., cited. 113 Lemroh Mining Company, operations in Butte County. 234; operations in VA Dorado

County, 256 Lewallen Ranch, San Joaquin County. 283 Lewiston district, placer mining in, 309

Placers, operations in Trinity County. 308 Liberty district, placer mining in. 293, 29 4, 298 Lightner mine, Calaveras County, 237 Iights Canyon district, placer mining in, 277

Creek, Plumas County, 277 Lima dragline exea\ator, 37

Lincoln district, placer mining in, 271, 276 ou

Gold Dredging Company, dragline dredge, photo of, 309 ; operations in shasta

Countv, 284 ; operations in Siskiyou County, 297-298 ; operations in

Trinity County, 309-310 Linden district, placer mining in, 283 „ . „„„

Lindgren, Waldemar, cited, 144, 152, 154, 157, 173, 179, 181. 233, 2oo, 269; drawings

by, 162, 177; quoted, 163, 170, 173, 174, 179, 184 Link belt dragline excavator, 37

Lithologic criteria, determination of age of placers by, 185, 180 Litsch, Robert, property, Shasta County, 283 Little Browns Creek, Trinity County, 305 Uttlejohn Creek, placer mining on, 304, 305 Live Oak mine. Placer County, 273 Living conditions, for small-scale placer miners, 18-20 Lobicasa Company, operations in Butte County, 234 ; operations in Calaveras County,

Lobicassa Company, operations in Plumas County, 277 ; operations in Sacramento

County, 281 ; operations in San Joaquin County, 282 Lode production, table showing ratio to placer production, 1848-1930, 158 Loftus Blue Lead Mining Company, operations in Sierra County, 287 Logan, C. A., cited, 36, 163, 233, 235, 255, 263, 271, 274, 277 Log-sheet in sample drilling, 225 Logtown property, Sacramento County, 281 Lombardi property, Calaveras County, 253

Long Bar Gold Dredging Company, operations in Amador County, 232 Point Mining Company, operations in Placer County, 274 tom, description of, 28-29 ; drawing showing, 28; in dragline dredge cleanups, 45;

separation of platinum metals, 139 ; treatment of beach sands, 79 Longwell, C. R., quoted, 187, 188, 191, 193 Lord, J., property, Mariposa County, 261

and Bishop, operations in Butte County, 234; operations in Calaveras County, 253 Lorentz property, Amador County, 232 Lorrie property, Butte County, 235 Los Angeles County, piacer mines in, 260-261 Lost Camp mine, Placer County. 273 Louis. Henry, cited, 137 Love Ranch, Placer County, 272 Lowden Ranch, Trinity County, 307

Lucky Charles Mining and Milling Company, cost of running drift for, 87 Lyons Ranch, Tuolumne County, 313

M

MacBoyle, Errol, cited. 263, 277

MacDonald. D. F., cited, 124

Macaulay, W. B.. cited, 260

Machado property, Mariposa County, 262

Madera Countv, placer mines in, 261

Magee, J. F., cited, 36

Magnetic separator, for sizing black sands, 77

Mahon property, Sacramento County, 281

Malakoff hydraulic mine, Nevada County, 268, 267

Malozemoff, P., Jigging applied to gold dredging, 63-72

Mammoth Mining Company, operations on property of, 315

Marine fauna, use in determining geologic age, 184

placers, 161, 168-170, 205, 207, 208, see also beach placers; possible areas con- taining, 150

sediments, Lower Cretaceous, 170 Marion dragline excavator, 37

:US i'(,A( i:k mining; for fjoi.D califoknia |RuI1. liio

Mariposa County, placer Initlei in, 261-2G2

Markets, for placer gold, 142-143

Marsh, K. A., property, Calaveras County, 252

Marshall. James, discovery of gold by, 255, 260

Martel property, Xe\ada County, 265

Martell Kavine, Kl Dorado County, 25C

Mats, used in moving dragline excavators, 37

Matches, Krangois E., diagram by, 190; quoted, 185

Mattison shaft, Calaveras County, 230

Matulich property, Amador County, 232

Max and Junction mine, Kl Dorado County, 256

Mavflower Cravel Mining Companv, operations in Placer County, 273-274

McAdams Creek, Siskiyou County, 293

McConnelJ Bar, Siskiyou County, 300

M(('ulloh property, Amador County, 232

MiKlroy mine, Calaveras County, 236

shaft, Calaveras County, 236, 237, 238

McCain. Roy, photo by, 259

Mcdeachin I'lacer Cold Mining Company, operations in Placer County, 273, 274-275; photo showing sampling of hydraulic bank, 275

McCee, W. J., cited, ISO

McCuire, A. It., partner in single-bucket dredge operation, 62

McCurk property, San Joaquin County, 283

McKinely, H. W., mining operations in Placer County, 275

McMillan and Company, operations in Tuolumne County, 313

MiQueen and Downing, operations in Amador County, 232 ; operations in El Dorado County, 256 ; f)i)erations in Sacramento County, 281 ; operations in Siski- you County, 298

Meadow Valley, Plumas County, 277

Measuring weirs, use in hydraulic mining, 98

Mechanical jig, 55, 63, 66

Mehrten Bros., operations in Calaveras County, 253

Melting furnace, in black-sand treatment, 79 Menke-Hess property, Tuolumne County, 313

Merced County, placer mines in, 262

Dredging Company, ojierations in Merced County, 262 River, placer mining on, 262 Merrill. C. \V., cited, 13, 45, 229, 258 ; quoted, 35 Frederick J. H., cited, 157 v.. P., cited, 174 Mertie, J. B., Jr., cited, 161 ; quoted, 165 Metcalf, L., cited, 96 Michigan Bluff, Placer County, 271

Midas Placer Company, operations in Calaveras County, 253 Midland Company, Inc., operations in Placer County, 275 ; operations in Siskiyou

County, 298 Milner. H. B., cited, 175

Milton placer mine, Nevada County, 203, 205

Mine and Smelter Supply Company, sampling machine made by, 33 Miners Ravine, Placer County, 272 Mining methods, placer, 11-146 Mississippi mine. El Dorado County, 257 Missouri Canyon mine, Nevada County, 269 Moccasin mine, Siskiyou County, 297 ; cost of equipment set up at, 297 ; dragline dredge

in use at, 34, 35 ; photo of dragline dredge at, 296 Mofflt, Fred H., cited, 168 Mojave desert, bajada placers in, 167, 207 ; geology of stream placers in, 157, 163, 171,

173, 207; Pleistocene faults in, 173, 204, 207 Mokelumne Tracers, Ltd.. operations in Calaveras County, 254 River, mining operations along, 252, 253

Sand and Gravel Company, operations in San Joaquin County, 282 Monarch Rand mine, Kern County, 260 Monighan dragline excavator, 34

Monit<jr, see f/iant

Montgomery property, Shasta County, 284 Monumental Creek, Placer County, 273 Mooney, Jose|)h, Ranch, F'lacer Countv, 272 Morgan property, El Dorado County, 256 Mormon Bar, placer mining at, 262 Morning Star drift mine, Placer County, 274

Morris Ravine Mining Ccjmpany, operations in Butte County, 234

Mother Lode, aerial map showing, 202 ; relation to Calaveras Central mine, 237 ; dis- trict. i)la<er mining in, 261 Mound City Cold Mines, Inc., property in Calaveras County, 239 Mountain Cold Dredging Company, operations in Amador County, 231, 232 Mud-pumping system, Yuba, description of, 59 Mulligan Ratich. Placer County, 271 Mullin and Company, operations in Tuolumne County, 313

-Hampton Dredging Company, operations In Tuolumne County, 313, 315 Munn property, Mariposa County, 261 Murdock Ranch, San Joaquin County, 282 Mutual mine. Placer County, 272

.'Uo

N

Xatoinas Company, jiy di-vcloiHiif nt by, Tl! ; dr.<lK.-s <i\viu-d l.y, ,',5 ; mining practices and eiiuipmont, 27,S-2.S0 : operations in Sacramento County, 1!TS- 280; photo showinK dredge of, 27!t iNeill, J. W., cited, U3 Neizert iiropcity, Nevada County, 265 Nevada County, placer mines in, 263-270

Irrigation Distiict, 27" Neville property, SisUiyou Coimty, 298 New Jersey mine, Placer County, 273 Newark mine, Nevada County, 269 Newcomb, R., cited, 13

Nichols Estate Company, property in J'lacer County, 27 7 Niece mine, Nevada County, 269 No. 5 Channel, Calaveras County, 237, 238, 240 Noble, E., and Sons, mining operations in Madera County, 2G1 Nordberg-Butler shovel, as used in Calaveias Central mine, 244-245 North Bloomfield, Nevada County, 26:i ; Mining Company, 202, 260

Columbia, Nevada County, 203

Cow Creek, Shasta C<ninty, 284

Fork hydraulic mine, Trinity County, 310-311

San Juan, Nevada County, 263 Northern Dredging Company, operations in Siskiyou County, 298 Northwest Development ComiKiny, operations in Sacramento County, 281

dragline excavator, 37 Nozzles, water discharge through, 105 Nugget Bar i>roperty. Trinity County, 305 Nuland property, Calaveras County, 253 Xuner property, Calaveras County, 253 Nunes property, Siskiyou County, 298

Occidental drift mine. Placer County, 272

Ohio Plat, Tuolumne County, 315

Okoro Mines, Inc., operations in Siskiyou County, 298

Olson, K. S., operations in Shasta County, 284

Omega mine, Nevada County, 265-260

Ophir district, placer mining in, 272

property, Yuba County, 315 Ore buyers, laws regulating, 143

Orick I'lacers, Inc., operations in Humboldt County, 258 Orlomo Company, operations in El Dorado County, 256 Oro mine, Placer County, 273

Trinity Dredging Company, operations in Siskiyou County, 298 ; operations in Trinity County, 311 Orono intervolcanic channel, 274 Oroville area, as source of gold, 5'2

Gold Dredging Company, operations in Butte County, 234 Osterman property, San Joaquin County, 282 Otter Creek, El Dorado County, 257

P. & H. dragline excavator, 37

Iacific Coast Aggi'egates, Inc., operations in Sacramento County, 282

Gas & Electric Company, 270, 285, 289

Placers Engineering Company, operations in Amador County, 232 Page buckets, used on dragline excavators, 37

Paleontologic criteria, determination of age of placers by, 184, 185 Palmyra mine, Nevada County, 269 I'an, description of gold-, 21-22 ; photo showing use of gold-, 14

-American Engineering Company, 279 ; cited, 63, 65, 71, 73, 79

-American Pulsator Jig, recent development, 69, 73, 74 I'anob Gold Dredging Company, operations in Placer County, 275-276 Pantle Bros., dry-land dredge used by, 49 ; operations in Placer County Paragon mine. Placer County, 273, 274, 276 Pardee, J. T., cited, 169 ; quoted, 169 Parker Ranch, Nevada County, 265

Parks Bar Company, operations in Yuba County, 315 Parmenter property, Trinity County, 305 Patchen property, El Dorado County, 256 Patman, C. G., cited, 139 Patsy mine, Kern County, 260 Pearch Creek, Humboldt County, 25 8

mine, Humboldt County, 258-259 ; photo showing, 259 Peele, Robert, cited, 9 7 Peninsular Ranges, placer mining in, 157 Penn property, Calaveras County, 253 Penrose property, Mariposa County, 261 Pension mine, Amador County, 232

350 PLACER M1NIN< 1 OR OOM) IN CALIFORNIA Bull. 13;")

Perrin Ranch, Nevada Ciuiity, 208, 26U I'erschbaker mine, Butte Cuunty, 233 I'erry Idlt-r, di scription of, 5!) ; photo showing, u8 Petroleum industry, use of new exploration methods by, ir>4 I'hillips property. Trinity County, 3oy , , . . ,

Phoenix river boat used for first drediing attempt m ("alifornia, ;) 1 , :2 i'hysiographic criteria, determination of age of placers by, ISj geology, in study of gold-bearing streams, 207 map of California, 158 terms relating to streams, 194-195, 197 Physiography, 153, 159 Picacho iiasin placer mine. Imperial County, 2o'J

lode mine. Imperial County, 259 Piedmont Dredging Company, operations in liiitte County, 234 I'ierano mine, Calaveras County, 230 Pierce, C. C, property, Mariposa County, 2i;2

J. T., Ranch, Aladera County, 2til Pillsbury, (J. B., cited, 145

Pilot Dredging Company, operations in Nevada County, 2tir,, 270 Pine Grove reservoir, Nevada County, 2ti5 I'ingree Ranch, Nevada County, 2G.S, 2G9 Piombo Bros. & Company, oi>erations in Butte County, 234 IMoneer Dredging Company, operations in Shasta County, 2S4 mine, old. Sierra County, 287 Project mine, operations in Sierra County, 2S7 Pipe, details for shipping, 101 ; photo showing installation for hydraulic mine, 100 Pipelines, cost and method of laying, 102, 103; i<ressure boxes on, 102; type used in

hydraulic mining, 100-105 I'ipes, flow of water through, 103, 105; type used for flumes in British Columbia, 99;

use of joints and valves on, 10_2 Placer burials, as means of preservation, 171

concentrators, operations in Kern County, 2(Hi

County, dredging on Middle Fork American River, 25<; ; drift mining in, 157 ; placer

mines in, 271-275 Development Company, cited, 71 ; operations in Butte County, 234 Exploration Company, operations in Butte County, 234-235 ; operations in Trinity

County, 311, 313 gold geologic processes in formation of, 173, 174; jigs used in recovery of, 63;

marketing of, 142, 143 jig, 55, 63, 66

machines, small-scale, 31-33

miners, number of small-scale during 1930's, 15

mining, small-scale, as supplementary work, 13-14, 18 ; districts, legislation regard- ing, 336; methods, 11-146; small-scale methods, 13-33 production, table showing ratio to lode production, 158 Properties Company, operations in Stanislaus County, 304 Realty Corporation, mining operations in Placer County, 272 reserves, geologic classifications of, 152 types, characteristics of the principal, 163, 165 Placerita Canyon, Los Angeles County, 260 I'laceritas Mining Company, operations in Amador County, 232

Placers, age of, 183-186 ; characteristics of principal types, 163, 165-170 ; diagrammatic cross-sections showing transitional stages in development of, 162 ; forma- tion of, 65 ; geologic classification of, 161 ; geologic processes in modifica- tion of, 171, 173 ; preservation of, 171 ; sampling of large, 31 ; table showing cysfB of prospecting for, 224 bajada, 161, 166

beach, 161, 168-170; Pleistocene and Recent origin of, 205, 207 depleted, 151 desert, 197 eluvial, 161, 163 eolian, 161, 167

glacial-stream, 161, 165

stream, 161, 163 Platinum metals, buyers of, 1930, 139, 140; in beach sands, economic Importance of, 169 ; recovery In dragline dredging, 45 ; separation, 77, 78, 131-135, 137-140; significance in placer deposits, 219, 223; tools for separation of, 21 Pleistocene, Red Bluff formation, 36 ; and Recent placers, 207 ; erosion, effect on Ter- tiary channels, 159; placers, 157. 165, 166, 201, 204, 205 I'lumas Countv, placer mines in, 277 Pole riffles, 123

Polk Ranch, Madera County, 261 Pontoons, for hull construction, 35, 59 Potholes placer mine. Imperial County, 260 Potter Ridge district, placer mining in, 261

Poverty Hill Proi'erties, Sierra County, 286, 287, 289 ; photo of dredge under construc- tion, 286 mine, Nevada County, 269 I'owell mine, Nevada County. 269 Power, for California dredges. 55 : for dragline dredges, 4 3 ; for single-bucket dredges, 62

-winch for dragline dredge, photo showing. 40 Prather. W. W., U. J. Alders and, mining operations in I'lacer County, 271 Preservation of placers, descriptions of various methods of, 171 Primitive gold recovery methods, photo showing, 14

I'rincess Tines property, Yuba County, SIT) ,„ , . .

rroduction of poid, lS4S-i;t14, talile showinR, lG-17 ; 1033-43. table showing, 35 Prospecting, for l)iiriert rliannt'ls, Ifil Public domain, placer niininp on, 20-21

lipsources Code, extract from, 33fi Puddling box, description of, 2S Pulsator jipr, 73, 74, 79

Pumpelly, Pvaphael, cited, 171 . , .. . . oo o-

Pumps, in draprlinf dredge upi rat u.iis. 4..; in mining, S.., Hi

pravel. used in llrilish Coliimliia, lOS

binvv diitv, in sampling: machines, 31 Putnam pnMi<rty, San Joaquin County, 2S2

liiaker Hill, Nevada County, 2i;!t Quart7, Hill mine, photo showing, IH

placers, operations in Calaveras County, 2r>3

property, Calaveras Cf)unty, 2'>') Quaternary, placers of the, 151, ir)7, 1C6, ISfi Quicksilver, method of carrying, 130; price of, 12ft; use in recovering gold, 31, 42,

f.;i, 70, 115, 120-13."), 130, 222. 223 Quincy district, i)lacer mining in, 277

R. & M. Mining Company, operations in Calaveras County, 253 ; operations In Yuba

County, 313 Raeburn, C, cited, lir, Rais Ranch. Shasta County, 2S4

Ralford Mining Company, operations in Calaveras County, 253 Rand Cold Dredging Associates, operation.s in Kern County, 260 Raiulsl)urg district, placer mining in, 260, 2S2 Ray Angle i)roi)erly, Butte County, 235 Recalp Comijany, operations in Placer County, 272 Recent and Pleistocene placers, 207 Red p.luff formation, barren gravels in the, 30

Dog Canvon, Nevada County, 200 mine, Nevada County, 209, 270

Hill mine, Trinity County, 307, 311

Raven property. El Dorado County, 256 Redding, dragline field southwest of, 3fi

Creek, placer mining on, 311, 313

mine, drawing showing Ruble elevator at, 108 ; phf)to showing Ruble elevator at, 110 Reddings Creek I'lacer, Ltd., operations in Trinity Countv, 311-312 Reed, Ralph D., cited, 171, 188

property, Calaveras County, 253 Rehberger property, Trinity County, 305 Reiner mine, Calaveras Countv, 23G

shaft, Calaveras County, 238 Relief Hill mine, Nevada County, 2G6, 207-268 ; photo of, 268 Reserves, placer, geolo.gic classification of, 152 Re.servoirs, for hydraulic mining, 00, 100, 112 Residual placers, geologic explanation of, 163

Retort, amalgam, drawing showing, 138; used in gold extraction, 136, 137 Rex mine, Trinity County, 313 Richards, H. M., operation.s in Tuolumne County, 315

R. H., cited, 77, 160 Richter, William & Sons, ojierations in P.utte County, 235 ; operations in Nevada County, 206 : operations in Sierra County, 289 ; photo showing dragline dredge of, 280 Packard, T. A., cited, 161 Ricketts, A. H., cited, 143, 323, 333 Ries, H., diagrams by, 177 Riffle claim. Sierra County, 287

-tables, used with dragline dredge, 42 Riffles, black-sand concentrates in, 77, 70 ; cleaning, in dragline recovery, 45 ; con- struction and use in hydraulic mining, 93, 115, 117 ; construction and use in rockers, 23: drawing showing block-type, 122; drawing showing dredge- and wooden block-type. 122; suitable for fine gravel, 127; suitable for shallow sluice streams, 125 : theor.\' of gold-saving by means of, 121 ; types suitable with undercurrent, 127 ; u.se in dip-box, 28, 29 ; use in sluicing, 29-30

dredge-, 123; drawing showing cross-section, 43

Hungarian, 45, 53, 115, 123

iron, 118, 124, 125 ; -.screen, 125

Jones, 73

lumber, 123

mercury trap, 53, 127

miscellaneous, 127

peeled-pole, 123

rubber, 33, 60, 125

:{.-,-J I'I.A(i:i< MININC I'OK (iOl.l) IN (AI.irOHNIA |BnlI. 13.")

Riffles — Continued

steel. 118. 124. 125

stf.nc, 124

'iim-pi'bble, ?,0

w I<-n-l.l..<-U. -.UK 12n-124 : diinviiiKs of. 122. 12.-!. 124 Uiin Cam 1 MfflniiiK Company, operations in Amador County, 232, 233 Rio Dt-vtlopmoiil Company, oix-rations in Tuolumne County. 313 River Pine Mininr Company, ojurat ion.s in Amador County. 232, 256; operations in

Kl Dorado County, 2.'ir. Rivers, diaj.'ram sliowinu di.wn-faiiltini; of lieil, 20.'. ; diagrams showing action of erosion

and snciioii iddi.s in, 177 ; ma;;netic mithods of tracing channels, 227 Rizzi Ranch, I'lae. i Connty. 271 Roaring llivir, .Shasta <'omit, 2S I : dredge, ruhlitr siil)stituted for iron in riffles. 42;

Kr. Cmnpany, .Shasta County. 2r,0 Robio lCst;ile, n)iniiig operations iii I'lacer County, 27"

Ranoli, Calaveras County, 2.'.:! Robinson Ranch, I'laetr County, 272 Rock Canyon Creek, 1*1 Dorado County, 2',:.

Rocker, di-scription of, 22-2<;, 2'.i : drawing showing construitlon f)f knock-down, 24 : drawing showing iiarts used in consti net ion of, 2.". ; photo showing use of. 14 Ropers Ranch. Placer County. 2 72

Romanowitz. Charl.s .M., niirl.cl-Iinc drrduiufj, r,l-GO Kosa.sco property. Tuolumn'' Countv, 31:' Rose. I. K.. photr) by, 27.'.

mine. Nevada Count.v, 2r.9

property. .Siskivoti Countv. 2;tS ; Vulia Countv, .11.". Pvos.-villc Cold Dr.dging Company, operations in Placer County. 276 Ross pro|i,iiv, Trinitv Countv. :'.(i."i Rossi property, .Sacramento County, 2S1 Rolting.-r property, Hutte Cf)UiUy, 2:!.". Rf)Ugher-jig, (18, 69. 7.'5, 74 ; i)hoto showing 4-cell block. 74 ; concentrates, necessity and

methods for testing. 67 : treatment of. 68, 69 Roughness coefhcient ii. table showing values of, 96 Roulard. V.. property, l-'resno County. 258 Ruble elevator. <lrawing showing. lOS; photo showing, 110 Ruby channel. 291

mine, Si.rra County, 2S.S, 2.S9-292 ; cited, 81, 89; photo of, 2S8, 289; photo of gold nuggets frfim, 290 Ripley Ranch, Amador Count y, 2.T2 P.ush Creek, Trinitv Countv, :!(I9 Russell. Isra<-I C, cited, 1 .S'7

Ranch, .Shasta Connty, 2S4

Sacchi. Spellenborg, and Kubli, operations in Siskiyou County, 298 Sacramento County, i)lacer mining in, 278-282 mine. Placer County,- 273 ]{iver, recovery of gold from, 28.T -San Joaquin drainage, hydraulic mining on, 203 Sailors Rar, Sacramento County, 2S1

Salmon River. North , placer mining on, 275, 293, 298; South Fork, placer mining on. 294. 298 district, jilacer mining in. 29.S

<;old Dredging Company, operations in Siskiyou County, 298 Mining Company, oiterations in Siskiyou County, 29:!, 29,s-:;o0 Salyer mine, Trinity County, :{12 : photo of liyilraulic mining at, 1(",6 Sampling, for hydraulic mining, 220; machine, I'hoto of Bodinson, 30; placer deposits,

31, 162, 219 Sampson, R. J., cited, 167, 259, 260, 282

San Andreas Cold Dredging Company, operations in Amador County, 232; operations tn Calaveras County. 253 Hernardiiio County, placer mining in. 282 Ruenaventura Mission. I.os Angeles County. 260

Carlos <:old Dredging Comiiany. operations in Nevada County, 270 Diego County, placer mining in, 157 Domingo Creek, placer mining on, 251 Kernamlo Mission, Los Angeles County, 260 Krancisipiito Canyon, T.os Angeles County, 260 (Jabrii'l Canyon, Los Angeh-s County, 260 district, i)lacer mining in, 260 Mission, Lr.s y\ngeles County. 260 Cruco Companv, operations in Shasta County, 285; and C. 10. Cruwell, operations

in San'.Ioa.piin County, 2S3 .J.ia.piin Countv. pla<er miniug in. 2.S2-2S3

Mining Conii>aiiy, operations in Merced County, 262 River, placer mining on. 257

Valley, drawing showing delta formation in. 198 Juan Cold Company, operations in Nevada County, 266-267 ; water-rights of, 267 Ridge, Nevada County, 266 Sand-drag, photo showing, 76 Sanguinetti Ridge, Tuolumne County, 313

IXDEX 3r)3

Santa Cruz, photo showing placer mining of beach sands at, 168

Felicia Canyon, Los Angeles County, 260 . „, „„ , j i

Sawin, Herbert A., Becker-Hopkins single-bucket dredge, 61-62 ; Deep gravela dredged successfully, 317-322 ; and Romanowitz, C. M., Biicket-hne dredfftng, 51

Scandia mine, Sisl<lyou County, 294-297 ; photo of dragline dredge at, 295

Scavenger jig, 68, 69, 73, 74

Scharr property. Trinity County, 305

Schwab claim, Placer Colinty, 274

Schwartz and Pedrazzini property, Butte County, 235 property, Butte County, 235

Scott paver, placer mining on, 298, 303, 311

Scotts Flat, Nevada County, 266 . ,

Screens, as feeder to undercurrent, 30 : for sizing black sands, 77 ; in Denver mechanical gold pan, 31 ; in dip-box, 27, 28 ; in long torn, 29 ; in rockers, 23, 26 ; standard size used on jigs, 66 revolving, in bucket-line dredges, 53, 55 ; in dragline washing plant, 38, 41 ; in G-B portable placer machine, 33 ; in Monighan dragline excavator, 34 ; in sampling machines, 31 wire, in Denver mechanical gold pan, 31

Scrubber, in G-B portable placer machine, 33 ; -section, in Denver trommel-jig unit, 31

Sears, Harry, cited, 236, 243

Sedimentation, stream, 153, 154

Seiad Valley, placer mining in, 300

Setter property, El Dorado County, 256

Shady Creek, Nevada County, 265

Shaft-sinking, for testing placer deposits, 221

Shafts, use in drift mining, 81, 82, 83

Shanahan Bar, Trinity County, 313

Shasta Countv, placer mining in, 283-285 Dam, 283, 297

Dredging Company, operations in Shasta County, 254; operations in Siskiyou County, 300

Shepard, Francis P., cited, 171

Shingle Springs, El Dorado County, 255

Shirttail Canyon, Placer County, 272, 274

Shuster. E. A., cited, 153

Sierra County, placer mining in, 285-292 ; Ruby mine, 81

Nevada, age of placers in, 183 ; block diagram showing effect of tilting on stream cutting, 199; diagram showing down-faulting of riverbed, 205; diagram showing epochs of Tertiary gravel deposition, 177 ; drainage system in, 187; drift mining in foothills of, 81, 82; erosion in early Tertiary time, 194; fossil plants in, 184: fossil vertebrate bones in, 185; geologic map showing topography of, 156 : geology of gold provinces in, 200-201, 204-206 ; geology of placer deposits in, 150, 152, 153, 159, 163, 173, 194, 204, 206; glacial placers in, 165, 166; gold in natural river sluices, 179; origin of gold in, 173 ; placer reserves in, 152 ; Pleistocene faulting in, 201, 204, 205, 207 ; stream deposition in, 191 ; stream patterns in, 197, 205 ; stream piracy during Tertiary time, 195; Tertiary placers in, 157, 163, 171, 173, 183, 200, 206, 207, 208 Northern, ancient channels of, 155 streams, glacial influence on, 205

Silva property, Siskiyou Countv, 298

Simpson, E. C, cited, 157

Sinclair Ranch, Calaveras County, 253-254

Single-bucket dredge, description of Becker-Hopkins, 61-62

Siskiyou County, dragline dredge operations at Moccasin mine, 34, 35 ; dry-land dredge operation in, 50; eluvial placers in, 163; photos showing mines in, 164; placer mining: in, 293-303

Six Bit Gulch. Tuolumne County. 313

Slab Ranch, Calaveras County, 236, 237 ; shaft, 239

Slate Creek, Yuba County, 315

Slichter, diagram by, 198

Sluice, photo showing, 126

-box concentrates, separation of gold and platinum from, 131

-boxe.s, 21 ; as rocker part. 23 ; at hydraulic mine, photo showing, 116 ; design and construction. 117; factors considered in determining width, 119; gold amalgamation in, 133 ; grades described, 120 ; handling of boulders in, 113, 114; in long tom, 28, 29; influence of grade on capacity of, 120, 121; influence of grade on prold recovery from, 121 ; maintenance of, 118, 119- 120; operating cost, 128; operating methods, 115, 117, 128; photo show- mg, 126 ; table giving size and capacity, 119 ; undercurrents installed with, 127; use in hydraulic mining, 115, 117; use with Giant, 112 short, 27 ; photo .showing, 27 -tailing, method of testing, 67

Sluices, double purpose explained. 117; grade and size govern daily yardage, 112; improved operation in bucket-line dredging, 57 ; installation of jigs on, 69-71 ; drawing showing jig arrangements, 70 ; use of auxiliary, in treating concentrates, 1 32 : use in hydraulic mining, 93, 113, 114 ; used with dragline dredge, 34, 38, 41, 42 ; used with dry-land dredge, 49, 50 ; use of mercury in. 117, 130, 131

Sluicing, description of, 29-30 ; in drift mining, 81

:{r)4 I'LACr.K MININC von COM) IN CAMKORNIA |P.ull. liM

Sm:ill II. .p,- niiiH", ria.-.T (..imtv,

-scuU: phircr mining' iiiftlxxls applitil tn l.laik >aii<l, Sinartsvillc- ilistrirt. pla< miiiinp in, Ml.'. Smith, Ciiuit, property, Siskiyou ('minty. 21(4

U. S., II. A. Smith and It. I. Smith, Dperatioiis in Trinity Ccunty. 312

.1. 1'., cited, 1.S8

I.. A., abstract from rei)ort by, 2tH-2il.'i

mine, Nevada founty, 2r.9

-Nnlti rman ("onipanv, operations in San .loarjuin t'ounty, 2s:; Smiths 1--I.it, i;i Dorail.i County, 2."..'.

I'oint. ria.-er <'oiiiity, :j74 .SnelliiiK dislrlet. placer niinintr in, 2f,2

i:<il(l Dredcinj; Cc.nipiin.v. operations in .Merced County, 2<i2 Solar! property, Ca la eras County, 2r,:',

South Ynl.a .Miniiif,' and I elopnu-nt Company, operations in Nevada County, 2r,.-. Southern l'a( ilic Kailroad, 276

SpilinK, in drift mining:, .S5, St., ST : in loose j;rou?id, drawings showing, S4 Spillways, on <1anis, <lit<'h'S, and reservoirs, SpririK Creek, Nevada Cfninty, 21(7 Spud Patch mine, San I'.ornardino Cr.unty, 2X2 Spurr, J. K., cited, KIS : diagram l.y, )7ti Stackers, used with draf;line di-edne, 4:!

Staj,':i" Mining Company, operations in Cala\eras County, 2'>.' Stanislaus County, placer niininR in, :'.04

Kiver, placer mining f)n, :!04 Starl)U<"k propt.Tty, 101 Dorado County, 2r)(i Starr mine, Ne\ailu County, 2119

Steep Hollow, Nevada County, 203; Creek, Nevada County, 2(i!t Steffa. Don, cited, 2.-)l ; quoted, f>:i, 85, 86 Stevenson, David, quoted, 188

Stewart Cravel Mines, operations in Tlacer County, 270-277 Stockton Ueservoir property, Calaveras County, 2.">:5 Stoll, (',. property, I'lacer County, 275 Stone riffles, 124

Strai) Ravine, Placer County, 276 Stratton property, Mariposa County, 2f.l Straub Manufacturing Company, cited, 7;t Strawberry Valley district, placer inininp in, 315

Stream deposition, 153, 17S-1S1, 1!tl-l!t4, 200; drawinj? showing several period.s of, 107; peoloRic explanation of. ]!tl-l!t4 ; of prold, 178-1. SI

erosion. 171, 178, 1S7, 1SS, l!i7; ReoloKical explanati<.n of, 187, 188

meandering. diaKi'am showing oxbow loops in, l'.i2

patterns. KeoloRic stiuly of, 181, 195, 107

piracy, diagrams showiiifr stapes in, IftO

placers. Keolopic exi.lanation of, 163, 105; Pleistocene fault origin, 204; Quater- nary oriRin, 151 ; Recent origin, 151 ; Tertiary, 208

pollution laws, effect on bucket-line dredging, 51

retention of gold, 178-181

sedimentation, 153

transportation, 188-191 ; of gold, 178-181 Streams, life history of, 180-200; physiographic terms relating to, l!t4, 195, 197 : Sierra Nevada, glacial influence on, 205 ; subdividing or anastomosing, diagram showing, 192 .Structural control, of streams, 195

criteria, determination of age of placers by, 183, 184 Stuarts Fork, lJast Fork of, placer mining on, 305 Sullivan angle-compound cf)mpressors, use in <"alaveras Central mine, 241

Creek, Tur>lunme County, 313 Sultana mine, Calaveras County, 237

Sumpter X'alley Dredging Company, i)liot<) supplied li.\ . 70 Suimuir Dredging Comi)any, operations in I'.utle County. 2:;5 : operations in Vul>a

County, 315 Sunshine mine. Trinity County, 307 Surveyors Mistake mine, Siskivou County, 30o Sutlers mill, di.scovery of gold at, 260

Swanson Mining Corporation, operations in Trinity County. 312 ; photo supplied by, 100 Sweetland, Nevada County, 263 Sweetwater Creek, 101 Dorado County, 250 Symons, Henry H., cited, 21 ; table of gold production, 10-17

Table Mountain, 185, ISO, 19!i, 202, 203, 20 4

Tadpole Creek, Shasta County, 283

Tailings, jig recoveries from, 67, 73 ; method of testing, 67, 73 ; photo showing stacking

with giant, 117; storage possibilities in hydraulic mining, 146; used for

road-bullding, 53 Tanner pro])erty, Calaveras County, 253 Taylor mine. Nevada County, 269

Tehama Dredging Company, o|)erations in Shasta <'ounty, 285 Tennessee Manxman drift mine, Sieira County, 292

M.V)

T::r!:[a;'d;a;!ranSl.';";:;l:;i'tio..s showing deposition. 177; placers in. 151. 152. 175, ISO. 20G

Oontral Hill cliannt;!. phot.. showinK, l;.l

channel and its delta, early map showing. 1 .(. ,,;.,,.v -.r ,i..v,.i

opment, 15!, Ifil; Sierra Nevada, 150, 1;>(, lb3, Id, l<.i, 183. 20(i. U,

gravels, economic signilicance of, 157, 159 ,-o ir-,.

physiography, relation to ancient-channel problem, li.3, 15 J

sediments, as bedrock in dragline operation, 3C

stream-piracy, 11(5

stream-placers, reserves in, 207, 208 Test pits, method and cost of running. 221 Testing set. for jigs, photograph showing, 72

tailing losses from dredges. 0(1, G7 Texas mine. I'lacer County, 273 Theller, J. H.. cited. 121 Tliew-Lorain dragline excavator, 37 Thoenen, J. K.. cited. 37 Thomas, diagi'am by. 177

property, Nevada County, 2G5 Thompson, J., cited, I'JO

J. F. Estate, property of. 27G

W. C. mining operations in Calaveras County, 253-254 Thorne property. San Joaquin County. 282

Thurman and Wright, mining operations in Calaveras County, 253, 254 ; operations in Mariposa County, 261 ; operations in Merced County, 2G2

C. H., cited, 254

Cold Dredging Company, operations in Shasta County, 284-285 ; photo showing. 284 Thursday No. 1 mine, Trinity County, 308 Tickell, F. G., cited. 175 Tiedemann mine. El Dorado County, 257 Tightner formation, 291, 292

'J'imber mats, for moving dragline excavators, 37 Timbering, in drift mines, methods of, 85, 86, 87, 88, 91 ; in loose ground, drawings

showing, 84 Tin, jigs used in recovery of. 63 ; stream-, tools for separation of, 21 Titan amalgamator, used with jigs, 7 4 'Jolman. C. F.. cited, 16G

Tomboy Gold Mines, operations in Calaveras County, 254

Tonopah-Belmont Development Company, lease of Vallecito-Western mine to, 24 8 Tout property. Trinity County, 313 Trabucco property, Mariposa County, 261, 262 Tractors, caterpillar, used with dragline dredges. 38 Trailer, as mounting for sampling machines, 31

Transportation, problems in mining bajada placers, 166 ; stream-. 178. 179, 181. 188-191 Treble Clef mine, Amador County, 233

Trebor Corixjration, operations in Mariposa County, 262 Trimble property. Trinity County, 305 Trinity and Klamath River fish and game district, legislation concerning, 334

County, buried placers in, 171; bucket-line dredge operations in, 54, 55; placer mining in. 305-313

Dredge, operations in Trinity County, 312-313

River, photo showing hydraulicking of bench-gravel deposit, 166 ; placer mining on, 258, 305, 309, 310, 313 ; bed, photo showing effect of early hydraulic mining in, 160 Trommels, construction and use in dragline dredging, 41 ; for dragline dredge, photo

showing, 40, 42 ; in Denver mechanical gold pan, 31 Tucker, W. B., cited, 259, 260, 282 Tungold mine, Kern County, 260

Tungsten, jigs used in recovery of, 63 ; tools for separation of ore, 21 Tuolumne County, photo showing andesite and breccia overlying volvanic-ash beds, 170 ; photo showing lava flow, 154 ; placer mining in, 313, 315 Gold Dredging Corporation, operations in Stanislaus Countv. 304 River, placer mining on. 304. 313

Table Mountain, aerial mosaic photo and index sketch of, 202, 203 ; diagrammatic geologic cross-section of, 199 ; geology of, 185, 186 ; photo showing surface of, 204 Turner property, Mariposa County, 261, 262

Twin Bar Mining Corporation, operations in Fresno County, 258 Two Channel mine, EI Dorado County, 257 Tye property. Trinity County, 305

Uncle Sam mine. Placer County, 273

Undercurrent, description of, 30; definition of, 115, 131; method of gold recovery by.

127, 128 United States Bureau of Mines, geophysical studies by, 227

Debris Commission, 273

Geological Survey, investigation of valuable minerals in black sands by, 77

Mint, instructions for shipping gold and silver to, 143 Upper Narrows debris dam, Nevada County, 263, 266, 267 Utica mine, Calaveras County, 237

IM.ACDK MINI.VC lOK (iOM) IN CAl-IKOUN IBull. l.M

Viil UaiRli, Ciilax . I as Connfy, 2r.2

Villdor DitilKiiiK I'oiiiimiiy, photo showing workiiiK-s of, I'lO

\'iilU'<ito Mining ('iimpanv. Inc., operations in Culavt-ras County, 247, 248, 2r)l

-\V'sti-iii min', drifting operations, 81, 83, 88, 247-2r>l, 254; geoloRy, 248; history. 2r.l ; jotalion, l*4N; prii<lu( tion, 248, 250-251 ; washing plant of, 249-250 Van Dyke, Modrdl, and W'arnt r, mining operations in l-l Dorado County, 257

Wagenen, T. K., <it.<l, 1 1 Vanciel, C. K.. operations in Calavt r.is County, 254 ; operations in Stanislaus County, 304 Ventura mine, Kl Dorado County. 257 Vesa Creek, Siskiyou County. ;tO() Victor mine, Calaxeras County, 2:!C Victory No. 2 mine. Kern County, 200

Viking Dredging Company, operations in Trinity County, 311, 313 Vincent, J., projierty, Sacramento t?ounty, 2S1 Volcanic ash, as roof in drift mine, 88 Volcano drift mine. Placer County, 27 7

Mining Company, Dtd., operations in I'lacer County, 277 Von der llellen. Wm., Dry-land dredge operations in Siskiyou County, 50

and Welilter, operations in Siskiyou County, 300

W

Wallace Bros, mine, Trinity County, 311-312

dredge, photo of, 230 Walloupa mine, Nevada County, 2G9 Waltz prop'rty, Mariposa County, 261, 2G2 WaMilaiid, Dart, cited, 227

War Production Hoard, limitations on gold mining, 34. Sit. 203. 268, 272, 289, 294, 315 Washing i)lants, in dragline dredge operations, 38 ; in drift mining, 81 ; in dry-land dredge operations, 50

all-steel, 39 Washington mine, Nevada County, 269 ; Placer County, 273

Water, duty in hydraulic mining, 112 ; flow through pipelines, 103, 104 ; heads required in hydraulic mining, 110, 112

current, drawing showing effect of stream-bed irregularities on, 155

rights, in hydraulic mining, 109, 146 ; on San Juan Gold Company holdings, Nevada County, 267

supply, cost of, in dragline dredge operation, 43; determined by seasons, liiH; legislation protecting domestic, 335-336; imi)ortance in hydraulic mining, 93, 94, 146; use in small-scale placer mining, 19, 26 Watkins, A. G., & Sons, operations in San Joaquin County, 283 Watt, diagram by, 177 Weaver Crock, Trinity County, 313

Dredging Company, operations in Trinity County, 313 ; photo showing dragline dredge of, 312 M'eaverville district, plac.r mining in, 305, 307, 313 Webber, Benjamin N., cited, 161, 200; quoted, 166, 167 Weber claim. Placer County, 27.4 Welsh, Jack, Ranch, Stanislaus County, 304 West mine, Nevada County, 269 Western Gold, Inc., operations in Nevada County, 267-268 ; photo of Relief Hill mine, 268

placer mine, Nevada County, 266-267 What Cheer mine, Calaveras County, 254 Wildcat Creek, Siskiyou County, 293, 303

Wilfley tables, used in black-sand treatment, 77, 79, 80 ; used in dragline dredge clean- ups, 4 5 William von der Hellen Mining Company, operations in Siskiyou County, 300 Williams, G. S., cited, 93

R., property. Mariposa County. 261

Bar Dredging Company, operations in Yuba County, 315 Wil.son, K. B., cited, 130 Wiltsee, K. A., cited. 234 Wiii.mler, N. D., cited, 96, 112

Winches, used with dragline dredges, 37, 41 ; used with hydraulic dredges, 114 Winchester claim, Placer County, 274 Wolf Creek, Nevada County, 267

vein, 292 Wcilliull Dredging Corporation, oi)erations in Calaveras County, 254 \\o,,(l strips, in riffles, 30

Woodbury, W. K., f)perations in Trinity County, 313 Wooden block riffles, 122, 123, 124 Woods Creek, Tuolumne County, 315

Works Progress Administration, report on small-scale placer mining, 13 Wriglit, W. Q., cited, 181 Wulff property. El Dorado County, 257 Wyandotte Dredging Company, operations in Nevada County, 268-269, 270

proierty, Butte County, 235

nf)?

Yager Ranch, Amador County, 233

Yale and Allyn property, Calaveras County, 254

You Ket, Nevada County, 269, 270

district, placer mining in, 253, 269 mines, Nevada County, 269-270

Mining Company, operations in Nevada County, 270 Young & Son Co., Ltd., operations in Calaveras County, 25 4 Yreka, City of, property, Siskiyou County, 298 Creek, Siskiyou County. 300

(lold Dredging Company, operations in Siskiyou County, 300-303 ; photos of dredges, Yuba bucket-line dredge, photo showing, 5 4 ; Trinity County operations, 55

Consolidated Gold Fields, bucket-line dredges in California, 56; cited, 71; opera- tions in Butte County, 235 ; operations in Merced County, 262 ; operations in Siskiyou County, 303 ; operations in Stanislaus County, 304 ; operations in Trinity County, 305 ; operations in Yuba County, 315-322 ; photo of dredges, 314 County, placer mining in, 315-322 ; single-bucket dredge being rebuilt in, 62 jigs, on bucket-line dredges, 55

Manufacturing Company, cited, 51, 61 ; descriptions of dredges built by, 303, 307 ; experiments with portable pontoons for hulls, 59 ; photos by, 230, 284, 286, 314, 316, 320 mud pumping svstems, description of, 59 No. 20 dredge, photos of, 316, 320

River, aerial photo of dredged strip on, 150 ; damming of, 263 basin, placer mining in, 315 Middle Pork, water-rights on, 267 South Fork, use of water from, 265-266

Zernitz, Emile, diagrams by, 198 ; quoted, 197 Zig-zag riffles, in sluices, 30

- — :;;tmer borroweb

MhB -.9

2003,

H( 1 7 1998 1 Rf CWEU

M 3 01996

Received

m - 9 1558

Mar 1

Psl

Jun3

R£i'

f*5

May 2 A 1993 Mm

200?

Psl

wR

Becewedi

Mr

htm*

PSt UcAUFOBNlA, DAVIS

04613 (5/97)M

University Of California Davis

3 1175 02237 1499

lJSL-itJiiiifiiiM

Placer Mining for Gold in California (Bulletin 135)

State Of California

Department Of Natural Resourci<3

Division Of Mines

Placer Mining For Gold In California

Letter Of Transmittal

Contents

Section Ii. Geology Of Placer Deposits 147

Section Iii. Prosi'Ecting And Sampling Placer Deposits— 217

Section Iv. Placer Mines By Cotnties 229

Appendix. Laws Affecting Placer Mining 323

Illustrations

Abbreviations

Ars

E.

H.

M.

M.D.

N.

R.

S.

S.B.

T.

W.

Section I

Placer Mining Methods

Small-Scale Methods

5.874J62 23.487.604 1 51.818,604 113.643.986 117.664.005

Iis

Small-Scale Methods

B

S2--'

Small-Scale Methods

A,

8Mai.L-Scat.E Mf.Tiiods

:V>

Siall-Scale Methods

Dragline Dredging

Division Of Mines

Bui-L. 135. Plate

19.S3

Si, 924

G8

Dragline Dredging

,1 M,

Cross Sect/On

Of R/Ffles

F

$50,(Kk) .$71,(Hm

Dry-Land Dredges

Placer Mtnino For 001,0' In California

Bucket-Line Dredging

Plackr Mining For Ooij) In California

2 S

Im.A< Fr Mining For Gold In Camfornia [. 135

Becker-Hopkins Single-Bucket Dredge

Jigging Applied To Gold Dredging

Hs

-Lateral Sluices

Rougher Jig

Scavenger Jig

I§

Shh

Notes On Jigs For Gold Dredges

Notes Ox Jigs For Gold Dredges Collins

Treatment Of Black Sand

Drift Mining General Description*

.S4

Vertical Section

1 " H

H

I I I J

Plan

88 Placer Mining For Gold In California [. 1M5

A Synoptic Presumption Regarding California'S Drift Mines

Hydraulic Mining

R

1 : 1 Ih : 1

Hydraulic Mining

1.S11 0.0()2S1