Economic Geology and the Bulletin of the Society of Economic Geologists 1911-12: Vol 6 Iss 8

1911 · Historical

Economic Geology and the Bulletin of the Society of Economic Geologists 1911-12: Volume 6 , Issue 8. Digitized from IA1518511-02 .

This 1911 document, Economic Geology and the Bulletin of the Society of Economic Geologists 1911-12: Vol 6 Iss 8, is preserved in the Mountain Man Mining Library for research and reference. Original source: archive.org.

Economic Geology

With Which Is Incorporated

The American Geologist

Vot. VI DECEMBER, 1911

ANALYSES OF SOME ROCKS AND MINERALS FROM THE HOMESTAKE MINE, LEAD, SOUTH DAKOTA.

W. J. SHARWoOoD.

The general geology of the mining region of the Northern Black Hills of South Dakota, and particularly that of the Homestake Belt, has been quite fully treated in Professional Paper No. 26 of the United States Geological Survey, by Messrs. J. D. Irving and S. F. Emmons. These authors, however, made but little mention of the chemical composition of minerals and rocks. Having had opportunity during some years to make or direct analyses of a considerable number of specimens found in and about the Homestake mine, I have thought it worth while to collect the results as a supplement to that part of their paper which deals with this deposit. For permission to publish them I am indebted to Mr. T. J. Grier, superintendent of the Homestake Mine.

The Homestake ore-body, as is well known, constitutes a long N.W.-S.E. zone in pre-Cambrian rocks. These consist of phyllites, mica schists, hornblende schists and other related varieties of regionally metamorphosed derivatives into which intrusive rocks have been introduced.

As presented in the following paragraphs the chemical composition of the different rocks which are associated with the ores, is first given, and later the individual minerals of ore and

country rock are presented. It is hoped that these data may throw some light on the nature of the changes which have taken place in the country rocks during mineralization.

Rocks,

The two varieties of igneous rock, mentioned by Irving and Emmons as occurring in and about the Homestake, are readily distinguished. The rhyolite porphyry, or felsite, is compact and nearly white, near the mine it usually shows but little evidence of crystallization, but at some distance grains of quartz occur several millimeters in diameter. Pyrite is invariably present or represented by oxidation products, the latter giving a yellowish brown color to the outcrops. Manganese dendrites are also common rear the surface. It is frequently met in the mine workings, in irregular bodies having a general tendency to parallelism with the ore-bodies and rocks of the Algonkian.

The trachytoid phonolite in the mine is rougher in texture, altering more readily. It occurs in one or two relatively small dikes cutting obliquely across all other rocks in the mine, and apparently having no relation to the mineralization. It contains no pyrite except in places where.it has been apparently mineralized by the same agency as the adjacent ore.

The schistose rocks vary greatly in character and only a few types have been analyzed, some of which have been considerably altered by atmospheric action.

Analyses Of Trachytic-Phonolitic Rocks.

Analyses of the phonolite (Nos. 1 and 2) agree closely with those of similar rocks in the district and with that of Warren Peak, Wyoming (Analysis 4). In all these the ratio of soda to potash is about 1:1.25. In a number of rocks mentioned by [rving from various localities in the Black Hills (Analyses B and C), the soda is in excess, the ratio averaging nearly 2:1, but otherwise the average composition does not differ greatly from the Homestake type.

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Analyses Of Rocks From Homestake Mine. 731

1. Phonolite dike intersecting Homestake ore-bodies, taken at 1,000-foot level. The sample taken was over 12 inches across, and showed alteration throughout, but one side was decidedly lighter than the other and had apparently been more leached. Large orthoclase crystals were present. Analysis I represents the darker portion.

2. Light colored portion of same specimen.

3. Soft weathered specimen, at contact with rhyolite (see analysis 17) and slate, in cut on B. H. & Ft. Pierre R. R. near S.W. boundary of Lead City, about one quarter mile from line of Homestake lead.

4. Light green rock from surface at Windy Flat, 3 miles S.W. of Lead. Mass of microscopic feldspar and light green needles of egirite.

5. Dike crossing Spearfish Creek, S.W. of Lead. Feldspathic with hornblende needles and a little biotite.

Analyses Of Phonolites.

Specific Gravity. 2.567 2 567 — 2.557 2.624 — — SCT En ea 55:04 55-76 58.26 55.73 58.47 55-14 56.34| 58.0 pS Sere 19.22 20.49 17.98 20.06 17.83 18.08 21.06 19.6 eerie Oxide . .). si 5 3-49 1.68 3.25, — ass 2.60 Ferrous Oxide — 4.23 3.63 1.62 4.20| 4.8 Manganese Oxide ) ——- — —- 0.10 — —- — Magnesia. . os oi. 00 1.40 0.89 — £:30.. 2,27 0.32 0.33 0.3 See re 2.62 3.51 —— 2.18 2.52 3.96 3.34 1.7 MOGR c sfh.8a hin oe tek 4.32 4.15 560 — 5.38 9.273 8.3 POCMRE of xis 5 eects 6.22 5.39 749 — 6.64 4.08 4.8 Water — 110°. ! 1.90 1.77 1§7 0.40 0.10 0.63 0.07 0.4 Water +110° 2.06 1.23 ) 3.70 Carbon Dioxide 1.54! 2.37) ae A li me si SSMU 515.30 0s bed ' Trace Trace. Trace: Trace Trace

'CO. was found qualitatively. Percentage stated loss on ignition minus water found by Penfield tube.

?Phonolite from top of Ragged-top Mountain, by F. C. Smith (Irving, loc. cit.), resembles this closely in composition, but contains CaO 1.93 per cent. and ignition loss 2.15 per cent.

® Analyses of 20 phonolites, tinguaites, etc., quoted by Irving (Joc. cit.), all show considerably more soda than potash; in many cases the ratio is two or three to one. In those of Lead district the ratio is 1 to 1.25 and 1 to 1.45; and feldspar crystals examined are evidently orthoclase.

A. Trachytoid phonolite, Warren Peak, Wyoming. Analysis by U. S. G. S. in Sundance Folio. Also U. S. G. S. Bull. 228, p. 102. Called Pulaskose in Folio, Syenite-porphyry in Bull. 228. Groundmass mainly feldspar, probably orthoclase (nepheline questionable, possibly some member of sodalite group).

B. " Trachytoid phonolite," large "dike-like" sheet, Squaw Creek, Black Hills, analyzed by Flintermann; J. D. Irving, "Contr. to Geol. of N. Black Hills," page 272.

C. Average of 20 analyses from the Black Hills (including B) tabulated by Irving.

ANALYSES OF RHYOLITE OR PORPHYRY FROM VARIOUS LEVELS OF THE HOMESTAKE MINE,

The rhyolite samples taken in the Homestake mine were in most cases seemingly fresh, but differed considerably in appearance and texture. Some were very close-grained and bluish white, like dense novaculite, others yellowish brown and almost earthy in texture; such differences as were noted in composition and alteration by no means corresponded with these appearances. A marked variation was noted in the ratios of soda and potash. The potash content of some samples is remarkably high, exceeding 12 per cent.; while in Washington's " Analyses of Igneous Rocks" only two examples were found approximating this percentage. A calculation of the norm of the specimens high in potash indicates almost exclusively quartz and orthoclase with a little pyrite.

In several cases certainly, in all probably, most if not all of the lime occurs as carbonate filling minute fractures in the mass. The pyrite occurs in two forms. In some samples, notably Nos. 6, 8, 9, some of it is found like the calcite, in films or discontinuous sheets of microscopic crystals coating the faces of minute fractures. All the samples examined, when not too much oxidized, also showed apparently original pyrite scattered in minute particles through the mass. Emmons states that pyrite " occurs abundantly even in the freshest specimens."

Considerable quantities, 50 to 100 Ibs. each, of samples 6, 8,

ANALYSES OF ROCKS FROM HOMESTAKE MINE. 733 and 9, were crushed and concentrated. In the preliminary breaking down each piece was washed and carefully examined, and all fragments having fractures or faces showing pyrite were trimmed or rejected. In this way nearly all the secondary pyrite, possibly introduced during the mineralization of the ore, was certainly excluded. The pyritic concentrates obtained from the remaining porphyry showed a very little ilmenite, magnetite, and hematite, with a few microscopic zircons, and contained an appreciable amount of gold, though too little to have any economic value. It is interesting to note that the gold found in No. 9, close to an ore body, differed little from that found in No. 8, 150 feet away, the difference being within the limits of experimental error.

In the analyses all sulphur was calculated to FeS, and any iron remaining was combined as Fe,O,. In a few cases this makes the Fe,O, too high, owing to the presence of iron introduced by the use of a cast-iron grinder.

Most of the determinations in the case of the porphyries were made by C. M. Kirby. Professor M. F. Coolbaugh, of the South Dakota School of Mines, was kind enough to verify the alkali determinations in one sample (No. 7) and obtained 0.13 per cent. soda and 12.00 per cent. potash, instead of 0.28 and 12.13 as given in the table.

56. Average of mass of about 50 pounds weight, found on dump, from one of the lower levels, probably 1,250-foot. Very white and close-grained, pyrite very fine grained. Shows a little purple fluorite and some minute zircons.

7. From 1,250-foot level, in main N. and S. header, near No. 8. Compact and white.

8. From 1,250-foot level, main header west side of ledge, at a point 300 feet north of main west crosscut from Ellison shaft. and 150 ft. from body of ore.

9g. Same locality as No. 8 but close to an ore-body.

10. From 1,550-foot level, west from Ellison shaft, close to 20 feet of ore. Bluish white, very compact.

11. From 1,550-foot level, east side of ledge.

12. From 1,550-foot level, a short distance west of Ellison shaft.

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Analyses Of Rocks From Homestake Mine. 735

13, From 600-foot level, east side of ledge, corresponding approximately in position to No. 11.

14. From 200-foot level, average of a number of samples from bodies of porphyry exposed in main drift.

15. From 100-foot level, average of several samples.

16. From 100-foot level, average of a number of samples.

17. From cut in B. H. & Ft. Pierre R. R. at S.W. boundary of Lead City, near to contact with slate and trachytic phonolite (see phonolite no. 3). Yellowish white, oxidized, and stained with streaks of oxide of iron.

Nos. 14, 15, 16, 17, have been appreciably altered.

D. Quartz-orthoclasite from Thiiringerwald, called Lebachose (Liparase) in Washington's Analyses, U. S. G. S. Prof. Paper, No. 14, page 142.

E. Granite-porphyry from Rodo, Sweden (Liparose). Jb., p. 150.

In connection with the occurrence of potash and soda in the wall-rocks of ore deposits it may be noted that Lindgren! found that in the wall-rocks of California veins the effect of the veinforming waters had been to replace soda by potash. Wright? states that in the rocks of the Treadwell Mine, Alaska, the mineralizing solutions have removed potash and introduced soda, together with calcite, quartz, and sulphides. His analyses® are as follows, omitting minor constitutents :

I. Albite-diorite (Treadwell) "apparently fresh,' from 110-foot level. II. and III. Relatively unaltered rock (Treadwe!l).

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No. 95. rs. 425. MOR DEE CONG ais GMs ticker we 63.01 58.53 64.36 PRR 9.5 claietasc he aae srt aicets 18.48 17.74 18.18 ES é-0s Chee e wa haabe eS 10.01 5.69 8.06 BBE © 5% nrvivi opts we OT OER- BY 0.39 3.90 0.89 NMED 54, skovsciosbig atereinee 6 ore oe 0.32 1.36 0.73 LOR Se ee aa 2.10 0.96 0.97 Calcite. eee sees 3.80 TABOR sae 2.70

*U. S. G. S. Ann. Rep. 17, part 2, page 148. 7U. S. G. S. Bull. 287, page 114. *1b., page Iot.

Only these three analyses are given, and the inference is drawn that the wide difference between the amounts of soda and potash in two of these indicates considerable variation in the unaltered rock from point to point.

In the case of the Homestake porphyry similar differences may exist between different sheets, but at the greatest depths attained the porphyry, though fresh-looking, shows evidence in the numerous calcite-filled fractures of its having been subject to the action of water. The analyses showing low ignition loss certainly suggest two principal types, one highly potassic, the other containing about half as much soda as potash. If Nos. 11 and 13 are from the same sheet, the latter on the 600-foot level has lost a considerable amount of soda, and some potash, more than the deeper seated specimens. Soalso Nos. gand 10, both from the immediate vicinity of ore bodies, contain somewhat less potash than No. 8, which is from the same mass as No. 9 but 150 feet from the ledge. The analysis of water (No. 28), from a deep level, suggests the leaching of potash in preference to soda.

Analyses Of Slate.

18. Gray micaceous slate from. near surface, east of ledge near south end of Homestake property. Typical fine-grained " woodyard slate." Specific gravity 2.771.

19. Black slate with much pyrite from deep workings. Contains carbon, and under microscope shows chlorite, quartz, garnet, biotite, hematite.

20. Represents samples taken systematically over a distance of 1,000 feet from north to south, near Ellison shaft.

21. Samples over a length of 100 feet east to west near Ellison Shaft, in Pierce ground.

22. Samples over a length of 500 feet north to south near Highland workings.

23 and 24. Averages obtained by mixing a large number of samples.

Although pyritic all are considered wall rock except possibly

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Analyses Of Rocks From Homestake Mine. 737

No. 19. No. 18 contains no gold. Others contain more than traces but not enough to be considered even as low-grade ore.

Analyses Of Slates.

Analysis No.

Depth, Feet. Surface.| 1,900 200 200 200 100 100 Pyrite (FeSs), per cent Trace 3.51 2.90 2.20 4.87! 4.61 4.05 UCR, SUPT CONIC, se c56s<) tise ate o's 66.08 50.36 63.90 62.20 54.20| 53.90 55.20 Ferrous oxide,! per cent.., 5.55 15.45 8.20 8.11 10.58} 10.32 II.14

Manganese oxide, per cent 0.0o4| — — — —!—/]—

OUR ET OEN Gs 0.50.4 5,65 6s e103 010-5 1.30 0.68 — 2.78 Trace Trace POS, DEF CONG e606 5:55. e' eas 5.30 5.08 — fre ake aS. 25

small proportion of the iron in No. 18, and a considerable proportion in the other, is in the form of ferric oxide; some specular hematite occurs in No. 19, and hematite and limonite in the others. All iron not combined as FeS, has been reckoned as FeO.

*Loss on ignition includes some sulphur from the pyrite. In Nos. 20 to 24 some of this loss is no doubt due to water taken up through alteration subsequent to the opening of the mine workings—some of the rock sampled having been exposed to moist air for 20 to 30 years.

Black Pyritic Slate.

In the vicinity of Lead a number of seams of black slate occur, containing much graphitic matter and a large admixture of pyrite, which in some instances probably contains marcasite. The material is black and opaque in the thinnest sections, except for occasional minute seams of quartz. Those tested for gold have shown little more than traces. An outcrop of this kind occurs on the hillside above Whitewood Creek, to the east of the Homestake property, and another on Yellow Creek, below Flatiron. At the latter place a tunnel has been run some distance on a nearly vertical seam, and water running from the tunnel is heavily charged with ferrous sulphate, which is no doubt responsible for the deposit of ferric oxide noticeable on the rocks of the creek bed. The sample analyzed was taken from @& prospect tunnel between Lead and Terry. Before analysis the veinlets of

pyritic material were removed, about 50 per cent. of the mass, but some finely disseminated pyrite remained.

Brack State, ANALysis No. 25.

Per Cent. CVS lt NO Gest eM R CIEE Lier KE OKO ich a: AOFM aT Pa 11.63 ROEHL 5s a's wists e ous bots va bsp REE RES ARO EAR ci wa ask 13.50 CakonaceOUs ANBTLET gc. sis Gpcku scbise eho se oo ssc 0s FOE AE 11.08 White insoluble residue, silica and argillaceous matter 62.74 BVBUCT Tis ssn aSeicams his ean ier RR GRA pam adm than eta ces 1.0

As 13.5 per cent. of sulphur is slightly in excess of the requirements for 11.63 per cent. of iron, calculated as FeSg, it is probable that a little sulphur is combined with carbon and hydrogen in the combustible matter.

Waters.

Normal Waters From The Homestake Mine And District.

Considering the extent and depth of its workings, and the area drained by them, the Homestake mine yields comparatively little water. Much of this is surface water entering the upper workings; the occasional flows met in successive levels at greater depths are apparently also due to surface waters following a few small fissures or channels. The rock in general is however permeated by moisture, so that in drilling it has comparatively little tendency to produce dust, and air entering underground speedily becomes nearly saturated with water vapor.

Analyses of waters from the mine (Nos. 26 to 29) sampled under normal conditions, as compared with water from other sources in the vicinity, show a considerably larger proportion of lime and magnesia, and a very much larger percentage of sulphates and chlorides. In the samples taken from streams flowing from the rock in the lower levels there is also a higher alkali content.

The chlorides are accounted for partly by the percolation of surface waters conveying drainage, partly by the effects of the excreta of nearly 1,500 men and 50 horses working under-of

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ANALYSES OF ROCKS FROM HOMESTAKE MINE. 739 ground.!' The sulphates are evidently derived from the oxidation of pyrite in the ore and adjacent rocks. This tendency is also to be noted in comparing the water of Whitewood Creek (Analyses 35 to 37) with that from other outside sources; the somewhat high sulphate figure in the creek water is attributable to water coming from the mines of Terry, and its chlorine to drainage from that town. At several points on the slopes above creeks and gulches tributary to Whitewood Creek there are prospect tunnels driven on seams of black pyritic slate (see analysis No. 25), from which flow small streams highly charged with ferrous sulphate which deposit ferric hydroxide by the action of air; the boulders in the main creek bed are strongly stained with limonite from this source. The water pumped from Spearfish Creek to the reservoirs supplying the mine and the city of Lead is almost free from chloride and sulphate (see analysis No. 39), and at times neither can be detected in it.

No strictly quantitative conclusions can, however, be drawn from these analyses, as the seasonal variation is very marked, in both the volume and contents of the waters of both mine and creeks ; a rational comparison would necessitate systematic measuring and sampling for at least an entire year.

Analyses Of Mine Waters During The Fire Period.

In 1907 a fire occurring in old timbered stopes necessitated the flooding of the mine to a point above the 300-foot level. Analyses (Nos. 30 to 34) of water samples taken during the subsequent unwatering are of some interest as showing how, in spite of a vastly increased influx of water, the percentage of sulphates and of total dissolved solids was at least quadrupled. No doubt this is partly due to some of the ore having been intensely heated by the burning timbers, partly to much of the water having been warmed, but I believe principally to the opportunity given for the water to leach freely through a large body (something

At the time referred to miners worked ten hours underground. The horses were permanently stabled in the mine. More recently nearly all the horses

have been replaced by locomotives driven by compressed air, of a smaller type than those which had long been in use in the main headers.

over a million and a half tons) of more or less pyritic broken ore standing in the stopes, and also through a much larger mass of broken waste rock (both slate and porphyry, all of which probably averaged I per cent. to 2 per cent. pyrite) used as filling for other stopes. At this period practically all the flow of Whitewood Creek, swollen much of the time by melting snows, was for over a month turned into the south end of the mine by a flume leading into the Savage Tunnel, while the pumping station was run at full capacity, and its supply, drawn from Spearfish Creek, with all the smaller streams available, was poured into the open cut above the fire area, or into other openings.'

In unwatering the mine some 80 million cubic feet, or 2,500,000 tons of water were raised in a period of about three months. Taking analysis No. 30 as probably a fair average of this water, it contained 2.5 & 1,115= 2,788 tons of SOs, or 1,115 tons of sulphur, representing the total sulphur contained in over 2,000 tons of pyrite. Incidentally, while making analyses of the samples of air mentioned by Yates as being taken in the mine during the progress of the fire, it was generally noted that there was a decided deficiency of oxygen—that is, the sum of the oxygen and carbon dioxide found was much below the normal 20.9 per cent. or thereabout, even after allowing for a small amount of carbon monoxide formed. This deficiency averaged at least 0.8 per cent., and is due either to the dissolving of some carbon dioxide in the water, or to the absorption of some of the oxygen by oxidation of sulphides and other ferrous compounds in the rock and ore.

The percentage of carbon dioxide in the air displaced by the inflow of water during the progress of the fire was at times very high; for ten consecutive days it averaged over 12 per cent., some samples reaching 15 per cent., while the oxygen was reduced to 5 per cent. While combustion does not normally go on in air in which so much of the oxygen has been consumed, it was no doubt aided in this instance by the proximity of highly heated

*See B. C. Yates, "The Homestake Mine Fire," Engineering News, Jan. 2, 1908, LIX., 1.

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Analyses Of Rocks From Homestake Mine. 74!

rock to the charred timbers, as tunneling in a caved stope in the fire area exposed large masses of incandescent rock. The presence of this large proportion of carbonic acid may have aided the dissolution of the alkalis, which were so abundant in some of the water samples from the deeper levels at this time, but the oxidation products of pyrite were probably more important factors.

It is unfortunate that. soda and potash were not separately determined in these samples, but the existing circumstances did not allow of elaboration. Qualitative tests on samples taken in the earlier stages of filling indicated that but little potash was then present in the water. This is of interest in connection with the great variations observed in the proportion of soda to potash in the rhyolite at different points in the mine. Some of the soda found was derived from the explosives used in the regular course of mining—the monthly consumption of nearly 150.000 pounds of dynamite,' containing about 45 per cent. sodium nitrate, or 16 per cent. Na,O, means the introduction each month of over 12 tons of soda, most of which is converted-into carbonate and left adhering to the broken rock—about a ton of milling ore being got for each pound of dynamite used. Judging from sample 5 the 2,500,000 tons of water must have carried over 1,000 tons of alkali, reckoned as Na,O. The million and a half tons of broken ore standing in the stopes had required about a million and a half pounds, or 750 tons, of dynamite, which would carry 120 tons of soda. An entire year's consumption of the explosives then in use would account for less than 150 tons of soda. A certain amount is attributable to human and animal excreta. Judging from the other analyses less than one tenth of this thousand tons of soda was present in the incoming water. Hence by far the greater part of it must have been leached from the rocks with which it came in contact.

Sample No. 30 was found to contain gold. Duplicate lots of several liters each were most carefully assayed by two different methods, parallel blanks being run on all reagents. In each case

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Analyses Of Rocks From Homestake Mine. 743

the result was a gold value corresponding to one tenth of a cent per ton (32 cubic feet) of water. The assay balance used turned distinctly with .0025 milligram.

Analyses Of Mine And Creek Waters.

Nos. 26 to 29 are samples taken from the mine under normal conditions, the first three being from streams flowing from crevices in the rock.

Nos. 30 to 34 were taken during the "fire period" in 1907, after the mine had been filled with water to extinguish a fire raging in the timbers in old stopes on the 600-foot and adjacent levels. No. 30 represents most nearly the average of the total 80 million cubic feet of water subsequently pumped from the mine, being a mixture of samples of the outflow at three points during the unwatering, at about the period when the middle of the mass of water was being elevated, the surface water then standing at about the 600-foot level.

No. 31 was taken after most of the water had been raised. No. 32 was entrapped in an electric light bulb broken by the pressure of the rising water.

No. 34 was taken from a current of water rising through the heated rock, and had a temperature of 49°C. (120°F.). All fire period samples had a strong odor, and gave reactions for ammonia, nitrates, and nitrites.

Nos. 35 to 39 represent the sources from which the water was taken to fill the mine at the time of the fire.

Results are given as parts per million (grams per 1,000 liters).

Since this paper was prepared for publication two other waters have been examined, both differing essentially from the others described.

No. 112 is a flow met in the 1,700-foot level, of perfectly clear soft water, the dissolved matter in which is nearly all sodium bicarbonate (800 parts per million), with a little silica, very little potash, and mere traces of lime and magnesia—the two latter being the essential constitutents of the ordinary mine and surface waters.

The other, No. 113, was collected from drippings below a mass of barren pyrite on the 300-level, and was essentially a strong solution of ferrous sulphate with some free sulphuric acid. Analysis indicates :

Free sulphuric acid (H2SO,) 0.95 per cent. EDS cEC HH: Cer a ae es 4.6 per cent. FeSO, 12.5 per cent. DCT Oi Fo RR ae eee 0.4 per cent.= 1.4 per cent AMON 5.5.05 oes seacws 5.0 per cent. iron sulphates 13.9 per cent

CUES CSR eee 9.55 per cent. Little lime, magnesia and soda, not determined.

Minerals. Chlorite.

The soft green mineral, apparently chlorite but locally known as talc, often occurs in masses which, when adjacent to quartz, exhibit a vermiculate structure at the boundaries. It is found also in the schists. One variety of quartz, of coarse grain and rough fracture, contains it in the form of extremely thin microscopic blades or plates.

Samples 40 and 41 are of dark green foliated and more or less contorted chlorite, associated with arsenopyrite in the " contorted ore" described by Irving. The purest material that could be separated still contained a small amount of arsenopyrite and a very little quartz.

Sample 42 occurs in masses of minute scales or plates of a distinctly lighter green color than Nos. 40 and 41. This sample was taken from a mass occurring mixed with pyrrhotite and magnesian siderite (see analysis No. 52) in a specimen of what is styled "massive ore" by Irving.?, The foreign material was carefully picked out, but a trace of the ferrous magnesian carbonate could not be removed; every trace of pyrrhotite was easily extracted by a powerful electro-magnet.

Analysis No. 43 is that calculated from the formula:

Al,O,, 2FeO, MgO, 2H,O, 2SiO,,

*U. S. G. S. Prof. Paper No. 26, pages 85 and 86. 1b.

ANALYSES OF ROCKS FROM HOMESTAKE MINE. 745 which agrees fairly well with the analysis, if we suppose part of the Al to be replaced by Fe'"'.

Analyses Of Homestake Chlorite.

Analysis No. aE Dark, as Dark, as Excluding Excluding Calculated

Found. Found, Sulphide. Sulphide. Light. Pc Silica, per cent 25.13 26.02 25.38 26.21 24.20 27.25 Alumina, per cent 24.98 23.76 25.23 23.92 20.90 23.05 Ferric oxide, per cent , Not sep. 1.88 1.89 4.27 Ferrous oxide, per cent. 32.44 30.40 32.76 30.63 32.34 32.45 Magnesia, per cent Not det. 7-99 am 8.05 9.42 9.11 Lime, per cent Trace 0.40 Trace 0.40 Trace Water, per cent 9.50 8.73 9.60 8.80 8.39 8.14 FeAssS, per cent 1.02 072 — — — TET ofl 99:90 99.52

The specific gravity of Nos. 40 and 41, after correcting for the arsenopyrite present, was 3.27 in each case. A little carbonic acid (not determined) was found in No. 42, none was detected in Nos. 40 and 41. All contain traces of MnO and TiO,, which are included with the Al,O, reported.

As these analyses do not agree with any that were found published, the molecular ratios were computed from them for comparison with the accepted formulas of some of the chlorites— silica being in all cases taken as 100.

Mo.ecutar RATIOs.

Homestake Chlorite.

a gone ge 42 amet toid. nite. chlorite ingite. stedite, Silica, per cent...| 100 100 100 100 100 100 100 100 100 Ferric Oxide ) —— 2.7 6.6 Kits 66.7 ee tee ae and ee fey eee oe Silica aa ar) in 2.00/ 2.50 2.00) 2.37, 2.17) 2.33 ish aisiseed . Racal ie Sama 3-55 2.85| 1 3. — 3-35

Hornblende (Cummingtonite).

The light brown hornblende, occurring in fibrous and radiating masses in the Homestake Mine was described as tremolite by Irving and Emmons.' In thin sections it is practically colorless or may show a faint tinge of green or brown, but it differs from tremolite by containing little or no lime and a much larger proportion of iron, while tremolite is essentially a lime-magnesia amphibole. The specific gravity of the Homestake mineral is also higher. Its composition as shown below (Analyses 44 and 45) agrees with either of the minerals anthophyllite or cummingtonite, and Professor G. D. Louderback, of the University of California, has identified it as cummingtonite by its optical properties, pointing out the very close agreement between the analysis of this and of the type mineral originally described from Cummington, Massachusetts.

Owing to the large proportion of ferrous oxide this mineral absorbs oxygen and chlorine very rapidly, and in large proportions if finely crushed. This accounts largely for the consumption of oxygen in the cyaniding of the Homestake tailings, and for the slacking and swelling of hornblendic ore in the mine.

Much of the hornblende in the Jess oxidized ore is nearly black or dark green, and contains more or less chlorite, biotite, and sulphides or oxides of iron (Analyses 46 and 47). Occasionally it is met in long soft fibers, forming true asbestos. Most of the asbestos examined has been contaminated with quartz, but one specimen from the 1,100-foot level contained portions which appeared quite pure, the fibers being fine and silky and varying in color from white to light ash gray, some of them eight inches long (see analysis 45). Some nearly pure masses of radiating hornblende of light brown color were taken from the 800-foot level. Under the microscope this appears to be practically free from quartz, but contains a little pyrrhotite, and in most areas small scales of biotite have been deposited in the angular spaces between sheaves of moderately fine hornblende needles. The

Loc. cit., pages 68 and 91.

Analyses Of Rocks From Homestake Mine. 747

ANALYSES OF HoRNBLENDE.

Hornblende

Brownish White Cummingtonite Fibrous Radial, Asbes- Radiating Cummington, Tera White Std'Texporee (Sant and

Analysis No. 1 ied vo Fibers. Brush).

phide.

44a 44 45 46 47 a G PUIINAS cst ee ee ee 1.54 1.55] 1.86] 6.87] 5.02 0.95 0.89 Manganese oxide 0.45! 0.451, 0.62 0.31 1.50: 2.77 ocd Paks ac cet 8.10 8.16] 9.86; 9.20] 9.50 10.29 10.31 SSSA ee eer, ee ee aera 0.04 0.95 Trace, 1.04 1.16 Trace Trace ei aaa gf BP lala tare Sin —-— 0.40!| 0.74 0.50 0.75 0.54 Roteah 6 6:i.kea1 seh, Rhee — Trace 0.73 —— Trace Trace A ES ge een homer: 1.682 1.707) O.— 0.14 —— 3.04 3.04 BPI bis apie sicticicoh atte $53 0.89 ° te) —

Specific gravity 3-387 3.37| 3.28 — 3.42 |Dewey

44a. 800-foot level. Light brownish white, in masses of small radial aggregates, containing a little pyrrhotite. 44b. Same, eliminating S as Fe;Ss, 800-foot level.

45. 1,100-foot level. Long-fibered white asbestos, silky, free from quartz.

46 and 47. Dark impure masses of radiating hornblende. Greenish black. Appears to contain both chlorite and biotite with iron oxide.

F and G. Analyses of cummingonite from type locality, by J. L. Smith. and G, J. Brush.

*Determined in another sample of similar material. ? Determined by Penfield tube.

portion analyzed (see analysis 44) was quite free from biotite and all visible pyrrhotite was separated by an electro-magnet. The darker specimens all contain either biotite, chlorite, or iron oxides and sulphides.

In the more oxidized portions of the mine the hornblende has altered considerably, becoming brown and soft. When masses of this somewhat altered material are thrown upon the surface by blasts in the open cut, they rapidly alter further under the influence of the atmosphere, exfoliating and forming soft green products, and finally disintegrating completely.

The following extracts, for which I am indebted to Professor G. D. Louderback, show the characteristics of the mineral species cummingtonite, as exhibited in the original type specimens.

C. Dewey!' says: "I have given the name cummingtonite to a mineral found by Dr. J. Porter in Cummington. It appears to be a variety of epidote. Its color is gray, sometimes with a faint reddish tinge, unless when acted on by the weather, when its color is yellowish. It is in indistinct prisms, with oblique seams like zoisite, and in radiated and fasciculated masses, which are composed of slender prisms. Luster somewhat shining or pearly. It is nearly as hard as quartz and sometimes makes a slight impression on rock crystal. Before the blowpipe it blackens, and a small portion melts, when the heat is very great, into a black slag, which is attracted by the magnet. Its point of fusion seems to be about the same as zoisite. After allowing for some absorption its specific gravity may be taken as about 3.42." " With quartz and garnet it forms a large mass in Cummington."

J. L. Smith and G. J. Brush, under the title " Cummingtonite —a Hornblende,"? describe authentic specimens from the type locality, contained in the Lederer Collection of Yale College, as follows: "Structure fibrous, resembling anthophyllite; luster silky; color ash-gray. It occurs in mica slate at Cummington, Mass." 'Their two analyses are given above (Nos. F and G).

Carbonates Of The Homestake Mine,

Carbonates containing varying proportions of lime, iron, and magnesia, are met with very frequently in the Homestake ore, and are perhaps most plentiful on the lower levels. The composition varies greatly, and the following analyses represent some of the extreme types. In the tabulated analyses mechanical impurities have been allowed for, and the bases calculated to pure carbonates, determinations of carbonic acid by ignition having been made to check these calculations.®

No. 48. Recent incrustation of calcium carbonate about an inch thick on the slate wall of a drift in the 200-foot level.

A Sketch of the Geology and Mineralogy of the western part of Massachusetts, etc.," Am. J. Sci., VIII. (1824), pp. 1 to 60.

2" A Re-examination of American Minerals," Am. J. Sci. (2), XVI. (1853),

pp. 41-53.

*In addition F. C. Lincoln mentions magnesite. Econ. Grot., VI.. 205.

Analyses Of Rocks From Homestake Mine. 749

Color slightly brownish. trace of sulphuric acid, 1.30 per cent. of water, and 1.34 per cent. of material insoluble in acid, were found in the sample.

No. 48B, the analysis of which is not tabulated, consisted of calcite in large clear crystals half an inch across, the rhombohedral faces of which were deeply etched, apparently by a solution of iron sulphate, a little ferric hydroxide being deposited on the upper faces. These crystals were obtained in large slabs, forming the lining of a fissure of considerable size, met in barren rock on the 1,000-foot level. It contained 99.4 per cent. calcium carbonate, and 0.6 per cent. magnesium carbonate.

No. 49. Material lining a vugg-hole in pyritic slate, found in Pierce stope 600-foot level. The portion of lining examined was about 0.4 inch thick, consisting of crystals of this carbonate, transparent quartz, some pyrite, and minute amounts of fluorite, galena and a telluride (not further identified) together with large thin plates of free gold, which were most numerous toward the surface of the crust of carbonate. The material analyzed contained 6.18 per cent. insoluble in hydrochloric acid and 0.05 per cent. water.

No. 50. Black carbonate. A black opaque material was found in a number of specimens, usually in patches filling the spaces between crystallized minerals. It apparently always contains carbonates and carbonaceous matter, sometimes evidently graphitized. Magnetite or specularite is sometimes present, the latter in a form easily mistaken for graphitic flakes. Pyrite or pyrrhotite is usually present.

The sample analyzed was apparently homogeneous, filling spaces between aggregates of radiating crystals of hornblende on the 600-foot level. Only about one third of the specimen was soluble in dilute hydrochloric acid. The dried insoluble residue was separately analyzed.*

No. 51. Pure white carbonate, resembling calcite, 700-foot level. This occurred in small masses showing repeated twinning due to strain, and cleaving to slightly curved rhombs. A very

Analysis 50B. Black carbonate, including insoluble portion.

small proportion was soluble in cold dilute hydrochloric acid; when treated with warm acid about 30 per cent. of pure quartz remained, no other enclosures were visible.

Anatysis No. 50. Caculated to 10co Parts

Found in too Parts Original. of Carbonate, Soluble in acid CaCOs 19.21 =5305 MgCO; 14.52 40.10 FeCOs 2.48 G85 MnCO; traces SiO. and AlOs 0.35 Total 36.56 Insoluble by diff. 63.44 Insoluble by weight 63.68 Found in insoluble FeS. 5.37 SiO: 37.86 Al.Os 6.50 FeO3 0.35 CaO 0.10 MgO trace Loss on ignition 10.92 less S 6 0.96, mainly combustible matter 22 Total 60.14 Undetermined 3.30

The undetermined includes alkalis, very small amounts of TiO. and MnO. and a little graphite not burned off during the ignition.

No. 52. Creamy white carbonate, near Golden Gate shaft, 800-foot level. This occurred in small masses perfectly crystallized and cleaving to well-defined cream-colored or light brown rhombs, which are somewhat strained and distorted. It was associated with quartz, arsenopyrite, and pyrrhotite, in what is termed "massive ore" by Irving. Some specimens formed rather large masses, black from included scales and plates of specular hematite and carbonaceous matter. One such mass contained coarse free gold, and fine gold was found in several specimens. This type is, judging by appearances, common on the lower levels, occurring in the "massive" and "contorted" ore, often associated with sulphides and chlorite.

No. 53. Brown carbonate, from West crosscut, Independence shoot, 400-foot level. This resembles some specimens of siderite,

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and similar specimens were found in some of the upper workings, associated with more or less oxidized and altered ore, sometimes filling cracks in barren pyrite. The particular sample analyzed was a granular aggregate of minute crystals, having a texture like that of lump sugar, and was associated with quartz, chlorite, and arsenopyrite, in rock of the average value. Under the microscope the carbonate was seen to be strained and shattered, the cracks being refilled with quartz.

Black Mica,

Very small flakes of what appeared to be biotite have been observed in a great many sections of the filling from various parts of the Homestake ore-bodies. Frequently they may be seen filling spaces between the needles of hornblende (cummingtonite), in which case they are often associated with particles of pyrrhotite. In only one instance were pieces found of sufficient size and purity to allow of satisfactory isolation. In this case (a sample of ore from the 800-foot level) a few small masses were obtained which yielded flakes about I cm. across, some of them having a roughly hexagonal habit. They were greenishblack, with resinous luster, more or less curved, the lamine flexible but not elastic, and somewhat resembling specimens of chlorite from the same deposit. They were associated with quartz and magnesian siderite, both of which showed evidence of pressure.

Small lenticles of quartz occurred between the plates, many of them adhering closely, so that only a relatively small proportion was obtained in a pure condition, about 300 milligrams being finally available.

When heated with moderately dilute hydrochloric acid the mineral is rapidly decomposed, leaving pearly laminz of silica.

It was analyzed with the following results, which, while obviously unsatisfactory, are given for what they are worth, no opportunity having occurred to obtain more of the material.

Fluorine was not determined, nor was any precaution taken to prevent its interference.

sm un mé SiO

Sili Alu Fer Ma Ma Lin Alk Wa

rit

Analyses Of Rocks From Homestake Mine. 753

Brack Mica, ANALysis No. 54.

Per Cent. Molecular Ratios. BARA kscgy tection cute sels kets 30.53 BEB ics oe du comstee 5 JN CETTE OR AP a 16.05 15.7 cai . DETLIC "ORIGE —F.0.054 wes chee 6.81 4.26 J te EEO Ferrous Oxides 28 sf as.es + 2Z DO 37.7 ) Manganese eh es Ea Rae Geet 0.25 0.35 i as 5 IPB SIA: So Satie keke ae we .areig 4.04 10.0 Dimes Pie, Ce eis 1.01 1.8 Sodaeen 2alxo cera. Bos 0.37 0.6 ) PGES BU eae Stab os 6.27 O65 73085: 3:00 3 Water (by Penfield tube)... 4.23 23.5 J

Garnet.

Garnet is frequently found in the Homestake ore, but seldom in large quantity, though it is almost impossible to examine a sample of the mill tailings under the microscope without recognizing a few particles. Great difficulty was experienced in isolating it from samples of vein matter, and all the specimens examined were much crushed and altered. It is common in some of the slate which has undergone only moderate alteration, in small grains, mostly much crushed, which are faintly pink in the unaltered portions, but are usually black from magnetite and manganese oxide which have developed in the cracks, or occasionally of lighter color owing to deposited silica.

Homestake Garnet. Garnet from Southern Black Hills, Analysis No. 55 56 Per Cent, Molec. Ratio. Per Cent. Molec, Ratio

SCAG sien cna ove 38.66 6.39 3.0 36.4 6.03 3.0 Aliaha AE 24.03 2.35 1.13 22.2 2.175 1.16 Ferrous oxide! 28.10 3.905 26.8 3-72 Magnesia 2.71 0.67 Trace — eee Not determined. Not determined.

'No separation made from ferric iron.

One sample, only moderately altered, was found in green chloritic schist from the Caledonia raise, 800-foot level, in 1907.

About 300 milligrams of light pink particles were obtained for analysis, fully 95 per cent. of the separated material having been rejected on account of enclosures.

Several specimens have been examined of a black mineral from the Southern Black Hills, often taken for tin oxide. These all proved to be manganiferous garnets, somewhat decomposed and full of cracks filled with oxides of iron and manganese. On treatment with dilute hydrochloric acid these oxides were easily removed; the residual mineral was pink, but in some cases contained free silica. One such sample, after treatment with acid, contained 16.7 per cent. MnO. Another specimen was associated with microcline, an analysis of which agreed exactly with that of typical microcline or orthoclase. This garnet, after extraction with dilute hydrochloric acid, was analyzed and the result is given for comparison with that of the Homestake mineral.

Fluorite.

Purple fluorite occurs very sparingly in the Homestake Mine, though it is common in the siliceous ores of the Black Hills. Two modes of occurrence have been noted.

1. It is not uncommon in the white porphyry near contacts with slate in the neighborhood of ore-bodies. Patches of minute crystals occur in fractures in the porphyry near such contacts, and occasionally it is found in the mass of the slightly altered rock. It is found more frequently in the friction breccia between the porphyry and pyritic slate, usually as small patches in the interior of fragments of altered porphyry.

2. In one instance a number of minute but perfect cubic crystals were found scattered in the calcitic lining (analysis No. 49) of a vugg on the 600-foot level, together with large flakes of free gold and a little telluride and galena.

Tellurides.

While tellurides have been recorded by F. C. Smith! and others as occurring in the siliceous ores of the Potsdam series, I believe *Trans. Am. I. M. E., XXVII., 404.

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Analyses Of Rocks From Homestake Mine. 755

none have ever been noted in the Algonkian schists, except in the one specimen last mentioned. Here a telluride containing bismuth, but not further identified, occurs in contact with coarse free gold in the carbonate (analysis No. 49) lining a vugg in pyritic slate in the Pierce ore-body, 600-foot level.

Other Minerals Recognized.

A single example of galena was found in the form of a few small cubes, occurring with fluorite, etc., in the vugg just described. The largest of the crystals were about 0.5 X 0.5 X I mm.

A few minute crystals of sircon were found in concentrating the sulphides from a large sample of porphyry from the lower levels of the Ellison shaft (see analysis No. 6).

Orthoclase was recognized in a few specimens of ore, as pointed out by Irving, but the amount obtained was insufficient for analysis.

Barite was recognized in the form of small grains concentrated out of certain mill products but was not seen in the ore itself.

Magnetite in microscopic octahedra was found in one or two slides cut from carbonate ore, and in concentrates from rhyolite.

Hematite in thin transparent scales occurs in carbonate in some of the massive ore.

Black oxides of manganese occur as dendrites in the porphyry and filling cracks in garnet.

Quartz was not analyzed, except one transparent specimen, of coarse grain, which left only a trace of residue when vaporized with hydrofluoric acid. Most samples contain visible enclosures.

Graphite was identified in a schist and in thin flakes in a mass of carbonate. It, or some graphitoid mineral, occurs in considerable quantity in some of the schists and certain portions of the ore. See analyses 19, 25, 50.

Pyrite.

Pyrite is abundant in much of the unoxidized ore of the Homestake mine, but is apparently unconnected with the value

of the ore. It occurs in several varieties and under conditions which make it probable that there have been several periods of deposition, or that its deposition has gone on for long periods together. While pyrrhotite can rarely be seen on the interior of particles of pyrite, it is very frequently seen attached to the surface of them, or near and curving round them.

An analysis was made of selected pieces taken from the West crosscut from Golden Gate shaft, 800-foot level. After crushing and removing siliceous matter, the pyrrhotite was removed as far as possible by a magnet, leaving a residue of apparently clean pyrite. A little pyrrhotite was evidently present in this residue, as it yielded hydrogen sulphide on treatment with very dilute hydrochloric acid.

ANALYSIS OF Pyrite No. 57.

Found, Calculated for FeSo, BD RCUNG BTAVALY 56 scone seuss e 4.83 Insoluble, per 'cent .0.55...005.5 2.56 SRO RPE COPNE suits.c5 ain wip wis ebaeice 46.31 MORE: ET ONE. .5.05.5.ui's case Sees 51.26 ISEDDEr. OFT CONE. 655s 00cs sca ssa he> .07 eeenic, Per GANG. Ls. Oh es trace SOA ET HOON ios swat aie aby bea trace Calc. to pure sulphide: IQ aha. Sunes vee aay cree oeNe ate 47.47 46.58 PORINAT 6 lo cath nists zaldens whee Sado ouN eS 52.53 53-42

The composition calculated for pure sulphide corresponds to that of a mixture containing about 94 per cent. by weight of FeS, and about 6 per cent. of FeS.

Pyrrhotite,

Pyrrhotite occurs plentifully in much of the Homestake ore, frequently associated with pyrite. On the whole it seems to be more abundant than pyrite in the lower levels, while the reverse is true in the less oxidized portions of the upper workings now remaining. It usually occurs in irregular grains scattered through the ore or rock, or else so mixed with pyrite or arsenopyrite as

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ANALYSES OF ROCKS FROM HOMESTAKE MINE. 757 to make it difficult to obtain a pure sample. Occasionally masses of considerable size are found associated with white quartz. It was apparently overlooked by Irving and Emmons, who state? "Beside gold the only other metallic minerals are pyrite and pyrrhotite,' but this was doubtless because their observations were almost entirely confined to the upper levels. While not readily distinguished underground, it is easily identified by its brown color, by being readily attracted by the magnet, and by dissolving freely in dilute hydrochloric acid. Most specimens on dissolving leave a residue of fine grains or flakes of pyrite, occasionally of arsenopyrite, with a little free sulphur.

Fic. 411. Mass of chlorite with pyrrhotite and occasional arsenopyrite, and lenticles of carbonate (CA) and quartz (Q). No pyrite recognizable.

Some specimens show a decided tarnish. Two such were tested for copper, yielding 0.04 and 0.05 per cent. Several specimens free from tarnish yielded mere traces. In two specimens which were carefully tested no nickel was found; a trace was found in another. The gold contents of selected samples of nearly pure mineral ranged from 0.025 to 0.10 ounce per ton, or say 50 cents to $2.00 value per ton, which was much below the average of the ore from which they were sorted. Arsenic can be detected in some specimens, from a trace up to 0.1 per cent., probably occurring as admixed arsenopyrite.

One characteristic mode of occurrence is shown in Fig. 411,

*U. S. G. S. Professional Paper No. 26, page 68.

which is one type of Irving's "contorted ore." A number of instances of its association with gold and with arsenopyrite appear in other figures.

A sample from the B. and M. shaft, 1,250-foot level, west crosscut, north drift, which contained a large percentage of nearly pure material, was roughly crushed and then sized by passing over sieves of 10, 20, 30, and 40 meshes per linear inch. Each fraction was separately concentrated, again crushed, and, the clean pyrrhotite picked out by a magnet. A few large tarnished fragments were separately treated. Another sample was taken from the Golden Gate shaft, 800-foot level. A third very clean sample was obtained from the mill.

PyYRRHOTITE. Analysis No. 58 59 60 61 62 63 Locality. 1,220-foot Level. 800-ft. Uncerlated tain, for Larger On 10 20 to 30, Through 20 to 30 cl Insoluble per cent 1.36| 3.32] 1.8 1.68 6.18 0.88 ETON DET COME. ows ce saescacs 59.90! 57.6 58.0 59.5? 56.14 59.5 Copper per cent 0.04 |S. ser.) Mote... 6 Ar. 0. Arsenic per cent Tr. Tr. Tr. Sei} TY. ar. Gold, oz. per ton 0.05; 0.05) 0.05 0.06 0.10 0.025 Sulphur per cent sees 39.55! 40.13| 40.94) 38.65 39.68 40.0 39.594

*In this case a little iron oxide passed into solution.

The clean mineral is therefore nearly pure Fe,S,; the finer grades yielding a slightly larger proportion of sulphur, owing to the presence of a little pyrite. The specific gravity of three specimens was found to be 4.54, 4.56, and 4.40.

Arsenopyrite.

An analysis was made of selected pieces of apparently clean arsenopyrite, many of them showing the characteristic crystalline

*U. S. G. S. Professional Paper No. 26, page 68.

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Analyses Of Rocks From Homestake Mine. 759

form and striations, which were found imbedded in dark green chlorite, on the 800-foot level. Under the microscope some

Fic. 412. Pyrrhotite, arsenopyrite and pyrite in mass of chlorite containing quartz.

pieces show fractures and slight displacement of the fragments, and a few minute enclosures of pyrrhotite are visible on polished faces. Pyrrhotite occurs in the chlorite near the surfaces of the arsenopyrite crystals, appearing in a plane section as curved streaks more or less nearly parallel to the boundaries of the crystals or curving round their angles. It was removed as far

ARSENOPYRITE, 64 A. 64 B. aie one Calculated for

Anaiptie Mo Per Cent. Soluble FeAss.

Found, Portion. Insoluble, mainly quartz. 00+ 1.80 — a CS ASSES aSOn gi nat Re rush Sal rare eran ear 35.10 35-74 34.32 RUMBLE h cove Wie: severely: cobra ste state: ofl cee ts fede 20.86 21.24 19.67 RI as ols 015s when secre eta techie None od —. Arsenic (by difference) eee00+ 42.24 43.02 46.01 Gold (ounces per ton 1.40) 0005 -0048 — pee

Silver, not determined.

Specific Bravity esesseeeeeeeees 5.87

as possible from the powdered material by an electro-magnet. A little gold was also visible (compare Fig. 423 and 425).

A quantity of ore from the same place, averaging 0.20 to 0.40 ounce per ton, was crushed, sifted through sieves of 10, 20, 40, and 100 meshes per linear inch, and each fraction was separately concentrated. The pyrrhotite was removed by a magnet and apparently clean arsenopyrite remained with a little siliceous gangue. No free gold was visible on panning, but after treatment with nitric acid a little could be seen. Each portion was assayed in triplicate, and determinations were made of sulphur and insoluble.

Arsenopyrite Concentrates,

Analysis No. 65

ee OE a ae eee Fraction. Onxo 10-20 20-40 40-ICo Through 100

SREER EES 9 5 50 00550105 6S 9 5x6 —O8r eq 1.06 0.96 0.525 Sulphur, per cent 18.75 20.24 20.35 18.66 7.92 Arsenopyrite per cent. calc.

at 21 per cent. sulphur 89.25 96.6 '969° BBig 37.95 Gold, calc. as ounces per ton

of clean arsenopyrite 0.907 1.70 1.093 1.08 1.39

A rich sample of highly arsenical ore from the same place carried 2.42 ounces of gold per ton, and showed free gold on panning after treatment with nitric acid. When some of this ore was crushed to 30 mesh and shaken with mercury it yielded the greater portion of the gold as amalgam.

A considerable number of samples from various points, carrying gold and arsenopyrite, were tested in the same way with similar results, showing that at least a majority of the gold was present in the free state.

Ores. General Composition Of Lode Matter.

In no way probably can a better idea be gained of the general composition of the lode matter than from analyses of typical mill runs of ore. The following represent the results of sampling runs of at least 50,000 tons, while one is a composite of over

tior size om

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Analyses Of Rocks From Homestake Mine. 70)

750,000 tons. As some of them have been computed by apportioning a number of analyses of smaller runs, or of classes of sized material, most of the percentages have been rounded off by omitting the second decimals.

The "insoluble residue,"' obtained by treatment with acids, averages very nearly 1.2 X silica. "Iron soluble in acids," including sulphides, oxides, and part of that in silicates, averages 0.75 X total iron.

Analyses Of Runs Of Ore.

7 Lg 72 73 74

Analysis No,

|Surface Ore. Pyritic. patie Paie ghey

DECC BIAVILY os cen cecees 2.85 3.0 2.95 2.95 About 3.0 Sulphur, percents os. ds veces 0.17 3.40 2.40 3.65 2.2 BRON RET OODLE. 6:9: 6.414) 6.60:0 0 18's 16.85 17.0 16.0 20.15 16.95 ECR, 290T CORE. 6/6660 cS bss 55.8 55-75 55-7 50.78 54.0 Alumina, per cent 8.45 6.56 7.7 9.7 9.9 Iron sulphides! (FeS.FeS:z), per

MME. ccc cack saab ees raat 0.32 7.4 5.2 5.75 4.8

Iron oxides,? per cent 23.1 B93 17.6 22.7 27.7 Magnesia, per cent 1.5 4.3 3.05 2.45 4.1 EAIBO, VET CONE, .5.0.5.5:4 siers-s o's 1.8 1.9 1.8 sag i 2.0 SOUR: PEP CONE. 6.0:8's ehoreienete v's O.5 Potash, per cent... des ovis veas aso — ma — 2 Water at 130°, per cent. 2.1 ; o— 1.7 0.2 Water above 130°, per cent... ano ee eee 6 8 Carbonic acid, per cent.4 3.9 ! "68 ee

Sulphur is arbitrarily calculated as FeS2-FeS (54 per cent. Fe, 46 per cent. S), except in No. 70, where it is all present as FeSo.

?Tron not combined as sulphide is calculated % to FeO, 4 to Fe.O; (4FeO, Fe.0; 75 per cent. Fe, 25 per cent. O), except in No. 70, where the proportions of Fe' and Fe"' are reversed. In the presence of pyrrhotite and appreciable quantities of manganese dioxide and wood-fiber it was impracticable to make a determination of ferrous iron.

Of the silica in No. 73 approximately 15 per cent. is quartz, as estimated by separation with Sonstadt's solution. In the other cases the percentage of quartz is higher, probably 20 per cent.

Water above 130° is by Penfield tube. Carbonic acid is determined directly in No. 3; in No. 70 it is taken as loss on ignition minus water by Perifield tube minus 4 of sulphur.

The material represented by analysis No. 70 was exclusively fully oxidized ore from the open cuts and upper levels. The others are mainly ore from the unoxidized zone, but all include more or less surface material.

In comparing the analyses cited, one cannot avoid being struck with the high average percentage of iron in the slates and in the majority of the minerals, which is reflected in the composition of the average ore samples tested. This high average iron content is strikingly brought out by plotting the various analyses on a dia-

Silica 50% Constituents 100 %

Fic. 413. Trilinear coordinate diagram showing composition of the principal constituents of the Homestake ore, and accompanying rocks, with regard to iron, silica, and other components.

gram with trilinear coordinates, the apices indicating respectively iron, silica, and all other components (Fig. 413). From this may be seen how relatively small is the variation in the general com-posit

previ numl on tl porti as sv

almc is an whe:

min abso For thro

bee: of rec smi sho sev ber bor

Analyses Of Rocks From Homestake Mine. 763

position of the ore from period to period, the analyses of ore previously tabulated, both oxidized and unoxidized, as well as a number of others analyzed, all falling within a very limited area on the diagram. It is also noteworthy that by far the greater portion of the iron is present in the form of ferrous silicates or as sulphides, the latter probably containing it in the ferrous state.

One result of the presence of so large a proportion of iron is the relatively high specific gravity of the ore, which averages almost exactly 3.0. This again, it may be incidentally mentioned, is an appreciable factor tending to low cost in mining and milling, when, as is usual, calculations of cost are based on the tonnage of ore broken or milled.

An incidental disadvantage of the large proportion of ferrous minerals is their tendency to absorb oxygen, which element is absolutely essential to the solution of gold in the cyanide process. For this reason it is necessary to force large volumes of air through the moist tailings at certain stages of the treatment.

Copper In The Homestake Ore.

Copper occurs only in very minute proportions in the Homestake ores. The statement of Emmons, the authority for which was not given, that concentrates contain only 0.05 per cent. of copper, has been amply verified. The highest percentage found in hand concentrates from typical sulphuretted ore has been 0.05 to 0.06 per cent. in one specimen of pyrrhotite, which showed a brilliant tarnish. Most other samples yielded mere traces. The amount contained in the native gold is extremely small.

On the other hand two small specimens of native copper have been reported from the shallower workings at the northerly end of the property. No doubt these are the result of comparatively recent secondary concentration. The tendency of even very small percentages of copper to concentrate by leaching was well shown in the case of a few tons of pyritic quartz, which was left several months exposed to the weather, and then showed a number of patches of green efflorescence, colored by copper carbonate. The original material averaged about one third quartz

and two thirds coarsely crystalline pyrite, a little magnesian siderite occurring between the masses of pyrite and some granular mispickel in the quartz. Occasionally, where recent seepage has taken place in the mine, small patches of malachite may be noted in cracks in the slate, together with limonite and crusts of calcium carbonate.

During and immediately after the fire of 1907, while work was confined to the thoroughly oxidized red surface ores, the copper in the solutions at the cyanide plants, and in the resulting precipitates, increased to several times its normal proportions. This does not necessarily mean that these ores contained more than an average percentage of copper; it was probably due, at least in part, to the fact that the carbonates and other oxidized compounds of copper are much more readily soluble in dilute solutions of alkaline cyanides than are the sulphide minerals.

The following table shows the proportion of copper to gold recovered in the metallurgical processes, as compared with that in the visible free gold of the ore, the former being summarized for a period of eight months working under normal conditions. The entire amount thus recovered is however very small—less than one part per million of ore crushed.

Ratio oF Copper To GOLp IN BULLION.

. Base Metal Ratio ae In free gold concentrated from ore by Trace up ) Total base metal, PRIA DART bake viens batcstetheett to 0.005 if partly copper. In mill bars from amalgamation of free gold on copper plates 05. 0.018 —— Principally copper. In refined bars from precipitation of cyanide solutions by zinc 0.034 Principally copper. In unrefined precipitates obtained from cyanide solutions by zinc 0.240' Copper only.

*This ratio varies considerably from time to time, generally tending to decrease as the proportion of unoxidized ore increases.

The copper found in precipitates is evidently derived from minerals in the ore, or partly from incidental sources such as the copper-cased caps or detonators used in blasting. A calculation based on the quantity of these used during the eight months under

cons mor nide fron

ing

The of i

sou bee:

stal in V yiel asst abs disc

der wit spe gol

wh site

sta

Analyses Of Rocks From Homestake Mine. 765

consideration showed that they would actually account for a little more metallic copper than was found in the entire mill and cyanide products for that particular period. A very little also comes from the amalgamating plates themselves.

On the 200-foot level a small amount of a recent gelatinous deposit was found, which had a bright blue color. Upon airdrying it lost about nine tenths of its weight. An analysis (No. 75) of the air-dried residue indicated approximately the following composition:

4CuO, 2SO3, 3SiO., 12H,O.

There was also a small proportion of CaO and CO,, and a trace of iron.

Carbonate and black oxide of copper occur on croppings to the southwest of the Homestake, and other copper minerals have been reported from a small vein on the northeast.

Free Gold.

Free gold occurs in many different associations in the Homestake deposit, sometimes as comparatively rich ore, but oftener in very minute quantities, the average ore for many years having yielded not more than 7 parts of gold per million. Its invariable association with silver in the form of an alloy, and the almost absolute freedom of the visible gold from base metals, will be discussed later.

Irving' describes its occurrence in leaf form and without evidence of crystalline structure in quartz, and also in chloritic ore with quartz, but in neither case associated with sulphides. One specimen from the chlorite is mentioned as containing a leaf of gold about one half inch wide and one sixty-fourth inch thick.

Lincoln? mentions three specimens of free gold, the smallest of which weighed about 150 mgm., and an occurrence with magnesite, quartz, and chlorite.

Devereux® says "I have seen larger pieces from the Homestake quartz than any I have known to come from the cement"

*Loe. cit., pp. 68 and &6.

Economic Gro.ocy, 1911, VI., 203-205. Trans. Am. I, M. E., X., 470.

or basal conglomerate. On another page he discusses the seemingly favorable influence of porphyry on the occurrence of gold in its vicinity, and on its free-milling character.

The accompanying illustrations (Figs. 415 to 426), which have been drawn to scale with an Abbé camera lucida, show a number of occurrences of free gold, in some of which it would not be readily seen with the naked eye in an unprepared specimen. On a polished surface it is however easy, after a little practice, to see with the unaided eye a particle of gold less than .oo1 inch (say .02 mm.) across, and to identify it positively with the aid of a pocket lens and a fine needle. A sphere of this diameter would weigh about .000,002 grain or .000,15 mgm. It will be seen that in most of the cases illustrated a little pyrrhotite occurs near or in contact with the gold. This is noteworthy in view of the fact that concentrated pyrrhotite is generally poor in gold (see analyses 58 to 63). Carpenter' states that "beds of pyrite often pass into pyrrhotite, and in so doing they always cease to be goldbearing." The deposits he had in mind when thus writing were probably not of the Homestake type. Arsenopyrite is also conspicuous in a number of these ores with visible gold. Rickard? says "the pay ore usually carries sulphides, of which iron pyrite, pyrrhotite, and arsenical pyrite are most noteworthy, and of which the last is more particularly the comrade of the gold." This is borne out by assays of some of the arsenical ore and concentrates, but on the other hand arsenopyrite is found in some barren lode matter, and, as mentioned by Irving, pyrite and arsenopyrite are often wanting in the relatively rich portions of the ore. No single mineral, or association of minerals, can be pointed out as essential to the finding of gold, as is evident from an inspection of the sections shown.

Gold Arsenopyrite Pyrite Pyrrhotite Carbonate

@Oo0O0

Fic. 414. Key to sulphides, etc., in following figures.

*Trans. Am. I. M. E., XVIL., 573. *"Stamp Milling of Gold Ores," 1897 ed., page 98.

Fi

pyrrl into

of ¢

Analyses Of Rocks From Homestake Mine, 767

e5 iLL

MM LL:0S5 incw

Fic. 415. Typical chloritic quartz (CQ) with transparent quartz (Q), pyrrhotite and gold. Gold is in small grains in the dark quartz and extends into adjacent dark green chlorite.

Smm

Fic. 416. Back of same section, about ys inch (1.5 mm.) thick. Large flake of gold in contact with small grain of pyrrhotite, in chloritic quartz.

T°?

AGGREGATE OF ex © ARTLY Re oV.AC

Fic. 417. Gold with quartz in mass of hornblende. Hornblende in radiating aggregates, at this point invaded and largely replaced by quartz, with occasional pyrite and scattered masses of iron-magnesium carbonate.

Pyrite

i' SOLD & TELLURIE

Fic. 418. Gold in large flakes, some showing crystallized surfaces, some associated with a telluride containing bismuth, and all occurring in a layer of clear crystalline calcite forming the lining of a vug. Between the cale@te and the matrix of pyritic slate is a layer of clear quartz with pyrite masses show-

A few minute cubes of fluorite and galena were also present.

The telluride in the lower portion of the cut is shown by diagonal shading crossed by broken horizontal lines.

ing cube faces.

and

tere

Analyses Of Rocks From Homestake Mine.

wim. "05 INCH

Fic. 419 Grain of gold with pyrrhotite in iron-magnesium carbonate (CA) and very coarse-grained transparent quartz (Q). " Massive ore.'

"05 Inch

Fic. 420. Small grains of gold with a little pyrite and pyrrhotite, in scattered carbonate, with coarse-grained transparent quartz and arsenopyrite.

MAWES ARSENOPYRITE Fic. 421. Small grain of gold with transparent quartz (Q) and pyrrhotite. in mass of chlorite (C). Much pyrrhotite present in very irregular masses, and arsenopyrite showing crystal outlines and small enclosures of pyrrhotite.

Fic. 422. Grains of gold at contact of pyrrhotite with crystals of arsenopyrite in dark chlorite. No quartz observed.

of a

Analyses Of Rocks From

Homestake Mine. 771

25MM... .10 INCH Sn

Fic. 423. Grain of gold and accompanying pyrrhotite filling crack in crystal of arsenopyrite in mass of dark chlorite. Much pyrrhotite present in irregular masses, and some pyrite in compact grains. No. quartz observable.

f 4. ARSENOPYRITE

y/ 5 / / 4 " / &

03 'iN /§ Ee . f Ls a Nef A ©) ° N / ; + BS 2 SS f f pou LS

1.0 4 0 SSS ee NG ie MM, INCH Ma en

Fic. 424. Same gold grain as shown in Fig. 423, more highly magnified.

Fic. 425. Gold and accompanying pyrrhotite filling crack between small masses of arsenopyrite. The grains of arsenopyrite, a few of them showing crystal outlines, and a little pyrrhotite in irregular masses, are disposed along the border of a mass of chlorite (C), at its contact with chloritic quartz (CQ), which is almost opaque with the enclosed chlorite. Beyond this is a larger area of quartz (QC) containing minute blades of chlorite, giving it a pale green color. In thin sections this quartz shows many seams of lighter green or colorless quartz, showing several periods of fracture and recementing. In the mass this quartz, containing chlorite blades, is rough and saccharine.

-L.o5 MM~ INCH

Fic. 426. Same occurrence of gold as in Fig, 425, more highly magnified.

M: decre reasc clusi or ul since hand redu eight ore i ore; to g! impr perce of a

Ai porti of w form

In large

Analyses Of Rocks From Homestake Mine. 773

Ratio Of Silver To Gold.

Mr. Emmons pointed out that in later periods there had been a decrease in the average value of the ore mined, as compared with that obtained in the early history of the mine; and discussed the reasons for such a change, concluding with the statement, which still holds good, " As yet it cannot be said that there is any conclusive evidence of a decrease in value with depth in the sulphide or unaltered zone."! Even in the few years which have passed since this was written various changes have occurred: on the one hand there has been the upward tendency of the wage scale, the reduction of the working day from Io or 12 hours to a uniform eight-hour shift, the increase of the average depth from which ore is raised, and slight variations in the character of the deeper ore; on the other hand changes in engineering practice tending to greater efficiency, increase in the capacity of the plant, and improvements in metallurgy enabling the extraction of a higher percentage of precious metal and therefore the treatment of ore of a grade formerly too low to admit of economical handling.

At the same time he called attention to variations in the proportion of silver to gold in the bullion produced, giving a table of which the essential portion is here reproduced in a modified form.

Table I.

Period Ratio Gold" TID SG Tesh CURSO Le aca S1i's aioe Dale chine hia a wiea antes .204 NO, eal ad ENO LED ovat q:s ,0-8 essa 6 Che winbipem areata seins .215 1882 , MEME Re 6 cous S:5'clece p e's;0i0's 9-4 e.ove tice eertt islets .217

(During this interval silvered plates were introduced into the mills. W. J. S.)

1897 tT Sere eee eee er .233 1898 2 2 SOAR COREL IN APH ae NE Mem Rear 251 1899 MOSMAN ie a sese sas coe biaoe Nath casbraldvarn eforwretciecatina 258

He went on to say:

In considering the earlier and later groups of years the decidedly larger ratio of gold in the upper over the lower levels would be accounted for by the superior solubility of the silver, in consequence of which a

*U. S. G. S. Prof. Paper 26, page 63.

larger proportion would have leached out, but in the last three years in the lower levels there appears to be a slight, though not absolutely certain, tendency for the proportion of silver to still continue to increase. It will be of interest to observe in the future whether this tendency still continues with greater depth. ... The other columns in the table were arranged for the purpose of determining whether there was any uniform change with depth in the proportions of gold and silver in the bullion. ... The figures are deduced from proportions of gold and silver which are tabulated in the reports for each bar of bullion. ... The average during one or more selected months has been given to represent the character of the bullion during the year. The bullion is remarkably free from impurities other than silver, the average of such impurities being less than 2 per cent.

The question thus raised merits further consideration. There are several possible explanations of a change in the ratio of silver to gold in the bullion produced, which was noted above as showing a marked increase between the output of the early eighties and the later nineties, and which in 1898-99 seemed to Mr. Emmons still to have an upward tendency. Of the several causes which may contribute to such a change it is not surprising that Mr. Emmons discussed only the one which was naturally most obvious to a geologist rather than to a metallurgist, and which is placed first among the four that suggest themselves here, and that he connected the increasing silver solely with the increasing depth of the workings.

1. To quote Emmons's words: "the superior solubility of the silver, in consequence of which a larger proportion would have leached out" of the ore in the upper levels when exposed to atmospheric waters.

2. Possible variations existing in the silver-gold ratio of the grains of native gold in different parts of the ore-bodies, or in different ore-bodies successively worked. Such differences may exist in the horizontal as well as the vertical distribution of the precious metals, or between the contents of the middle and exterior of an ore-body, and might be due to variations in the composition of the mineralizing solutions at succeeding periods, or in the nature of the precipitants.

larg trac

ing

and the

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mo! flov the whi gol lar

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sibl sok fro thu rec cip of

prc

dot mo ing cot

Analyses Of Rocks From Homestake Mine. 775

3. Changes in metallurgical practice whereby a somewhat larger proportion of silver, as compared with gold, may be extracted from the ore than in former times.

4. Changes in metallurgical practice whereby silver, not belonging to the ore, is introduced into the bullion.

It is perhaps best to take up these possibilities in reverse order, and to begin with a brief outline of the metallurgical practice of the Homestake mills.

Outline of Metallurgical System.

After a preliminary breaking at the shaft mouth, the ore is crushed fine by stamps, 1,000 in number, with the addition of about 10 times its weight of water and a minute proportion of mercury. A small amalgamated copper plate in each five-stamp mortar catches part of the gold; the pulp then passes a screen and flows first over a row of amalgamated plates of plain copper, and then over two or three similar sets of plates, the upper surfaces of which have been first silver plated and then amalgamated. The gold amalgam collected by the various plates is removed at regular intervals, and most of the gold is collected in this form. The tailings are then separated by classifiers into about 60 per cent. of relatively coarse "sand" and 40 per cent. of fine "slime," each of which is collected separately, freed from water as far as possible, and treated with a weak solution of alkaline cyanide to dissolve most of the remaining gold, which is finally precipitated from solution by means of zinc dust. Over 4,000 tons of ore are thus treated daily, and about 94 per cent. of the contained gold is recovered, some 70 per cent. as amalgam and the rest as " precipitate," each product being refined separately. A small amount of silver accompanies the gold in the ore and in the various products.

In taking the amalgam from the silvered copper plates, as is done every day or two, a small portion of the plating is also removed, slightly increasing the proportion of silver in the resulting bullion, while in the course of time the coating of silver becomes thin and less efficient. After several years' use the plates

are therefore electro-silvered again, but before re-plating any remaining silver and amalgam are mechanically removed, and the coppery mixture thus obtained is refined, yielding bullion high in silver. If this is worked up with the regular mill bullion, the ratio of silver to gold in the product is correspondingly further increased.

Prior to 1896 silver-plating had not been in use; it was introduced in 1897 and the early part of 1898, since when it has been constantly practised, and the area of copper thus plated has been somewhat increased from time to time. The amalgam obtained from the silvered plates is a relatively small fraction of the whole—possibly one fifteenth of the entire value.

Changes in Metallurgical Practice Whereby a Larger Proportion of Silver may be Extracted from the Ore, as Compared with Gold.

It has been repeatedly observed in stamp-mill amalgamation that there is a tendency for bullion obtained from the amalgam caught nearest the stamps to have a smaller proportion of silver than that obtained on the plates at a greater distance from the battery.1. Generally the coarser gold is caught in the mortar or at the head of the outside plates, the finer at the more distant points. If therefore the finer particles have had more silver re-remarkable

instance of this kind is recorded by Keijiro Nakamura, metallurgist of the Besshi Copper Mines, Japan (Mining and Scientific Press, Dec. 29, 1906, XCIII., 790). At the gold mines of Sado, Japan, gold occurs as a natural alloy with silver, in the ratio of 580 to 420, and the beach gold, resulting from erosion of the same deposit, has the same ratio. In the stamp mill the bullion from the mortars contains gold and silver in the ratio 1: 3, and the silver increases with the remoteness from the battery until, after passing various amalgamating devices, some of the amalgam contains twelve times as much silver as gold. This is ascribed to the gradual decomposition of argentite by mercury, in its passage over plates, pans, etc.

Similar but less extreme effects have been noted by A. J. Clark (Trans. Am. I. M. E., XXIX., 459) in the milling of Homestake ore, and by R. T. Bayliss (Trans. Am. I. M. E., XXVI., 38 and 1049) at the Drumlummon Mine, Montana. In the latter ore silver sulphide and complex sulpharsenides occur together with free gold. The late A. L. Collins also observed the same tendency at Black Hawk, Colorado, and at the Reynolds mill, North Carolina (Trans. A. I. M. E., XXVI., 1042, and XXIX., 1041).

Nn

Analyses Of Rocks From Homestake Mine. 777

moved by natural atmospheric leaching than the coarse ones, one would expect to find a smaller proportion of silver on the more remote plates. Actually we find the reverse. It has been suggested that the anomaly may be due to the presence of silver minerals, sometimes unrecognizable, which are more slowly affected by contact with mercury than is the readily amalgamable native gold.

The gradual increase in the area of copper piates used in entrapping amalgam in the earlier years of milling, and before the era of silver-plating, may have contributed to the slightly increased proportionate catch of silver which was noted by Emmons for successive years in the earlier periods. See Tables I. and II.

During recent years (since 1899) another factor has come into play—the introduction of cyanide leaching; this has materially increased the relative production of silver, but cyanide bullion was not produced during the periods discussed by Emmons, and it has been carefully eliminated from the data considered in the present paper. It will of course profoundly affect any future similar comparison based on the total bullion output of the mine, as the cyanide bullion has a much higher silver-gold ratio than that of the average mill product.

Changes in Metallurgical Practice Whereby Silver, not Belonging to the Ore, May be Introduced into the Bullion.

As noted above, the practice of electro-plating a portion of the copper plates with silver, which facilitates the catching of the finer particles of gold, was actually introduced into the Homestake mills during 1896-97, and is still in vogue.

To exhibit adequately the influence of this prattice, and also to throw some light on the preceding and next succeeding sections of this discussion, the following table was prepared. This shows the silver-gold ratio of bullion obtained by amalgamation for periods including those discussed by Emmons, and some later years, but also giving as far as possible data for separate mills, treating ore at one time from different ore-bodies or different portions of ore-bodies, but which were later incorporated with the present Homestake company. Further, the figures were obtained

by averaging longer periods, usually one or two entire years, except when shorter terms are mentioned; this obviates errors due to occasional variations which may creep in when one considers the output of a month or two only. Braces indicate the consolidation of the mines or mills.

Table Ii. Silver

VALUES OF RATIO or IN BULLION OBTAINED By AMALGAMATION.

Home: High: end. ie 8Gale-

Period. stake. land Terra, wood. Smet. donia.

EG h6 PA wi oh Ahie6 6.00 6-0/8 Aa OHO E SO 0.196 0.175 — — — ER inka 4 afk dds ssp te ee oh 0.207 0.176 0.175 SUR INS he aie sa pccis 6,5 6 spa aok hs oe 0.197 0.184 0.198 0.218 —— SNES WiaS' eu chin Sb ated kCS%6is be wee Ok 0.193 0.197 0.210 0.233 PUMRREM CM Sitetivs 5 Ss/sius S65 bv oe wha emi 0.210 0.221 0.210 — 1896: four months prior to use of silvered

1898: four months next after installation Y

MAELO LAER 0 nso. 0 8.19: 0 ¥00°9 4:08 0.232 0.242 BO00s Mipit MOMENG. 6s oi ieee elec chee' 0.267! RRR eats sak b 30 vic's.c0as Rae bA0S oe © 0.265

calculation, deducting the average silver introduced by electroplating, based on several years' experience, indicates a net silver ratio of about 0.215 for the amalgamable gold of this period. The bullion obtained by cyaniding mill tailings during the same period showed a silver-gold ratio of 0.433; this bullion varies from time to time, the ratio ranging from 0.33 to 0.45.

The most obvious features in this table are: first, a rather sudden increase in the ratio very early in the operation of each mill; then a very slight upward tendency, until the introduction of silvered plates when a very abrupt rise occurs; finally (compare Table I. for 1898-1900) the ratio remains practically constant from 1900 to the present time.

Variations in the Silver-Gold Ratio of the Grains of Native Gold Occurring in Different Parts of the Ore-Bodies, or in Different Ore-Bodies Successively Worked.

Such differences in horizontal rather than vertical distribution are certainly suggested by the following table adapted from W.

e

a

Analyses Of Rocks From Homestake Mine. 779

B. Devereux on the authority of G. H. Hewitt,) giving a series of average assays of bullion from mines on the Homestake lode, ranging from south to north, prior to 1882.?

Table Iii.

FINENESS OF MILL BuLLIon Prior To 1882.

Gold. Silver. ! Base Metal. Ratio Tica' Homestake? (fo 0106s 820 170 10 0.207 BUIBHINA 5.0 acs bods vat 830 155 15 0.187 MENA 6.5 oo 68. bre Rap Wis Fela Bah 825 160 15 0.192 DeGd Wood so. 5. Sycica. sles laste 850 140 10 0.165 A Ce oe er ee 820 170 10 0.207

At this time no complication was introduced by the silvering of mill plates, so that the ratio of silver to gold should represent

"Trans, As TOM CE. OX, A605.

7 A similar variation has been observed in the Witwatersrand mines, ranging from east to west. As electro-silvered plates are not in use on the Rand, the ratio of silver to gold is not affected by the amalgamation. The copper

Gold. Silver. Copper. pn Silver Amalgamable Gold Gold' Cyaniding Gold Rand May Consolidated 884.0 113.4 2:5] 0:5; -)osray*t 1.81 POE err wis cists oiecs 6.0: 926.0 67.4| 6.3 0.3 0.073 Lancaster Gold: Rand Battery Reef loro.0| 85.7! 3.5 0.8 0.094 a Mines Princesses oic-si6s seas 924.0] 72.9 33 0.8 0.079 Roodeport United: Main Reef 1970.0] 29.8| o. 0.2 0.031 3.02

found depends to a great extent on the detonators used in mining the rock milled, and hence tends to appear high in mines having hard rock or narrow stopes.

The above figures are on the authority of Dr. J. Loevy (Sudafrikanische Wochenschrift, Berlin, 1899, No. 371, and Jour, Chem. Metall. and Mining Soc. of S. Africa, Dec., 1904, V., 152) except the last column which is taken from G, Andreoli (Jour. Chem. Metall. and Mining Soc. of S. Africa, Sept., 1904, V., 73). Andreoli states that the gold of the westerly Roodeport district has not only a much higher percentage of gold than the older Rand mines but is coarser, as evidenced by the larger percentage of gold found in

closely that of the original native gold, at least part of the 1 or 1.5 per cent. of base metal being derived from the copper plates.

A comparison of the different columns in Table II. for any given year, especially comparing the Caledonia or De Smet with other mills, shows a similar variation. The De Smet mill was formerly supplied with ore from the most northerly portions of ground worked, and the Caledonia from an ore-body situated considerably to the east of the other workings. Some further data are given in Tables V. and VI.

Differences in the Proportions of Silver and Gold in the Particles of Native Gold in the Ore Obtained from Different Levels.

Such differences, if actually found to occur, might be attributable to differential leaching of the two metals by surface waters, but might also be explained by differences in the conditions of

Assays Of Placer Gold.

Ratio,

Gold. Silver. Silver Gold Placer gold panned from gravel in bed of Silver| Creek, Lewis & Clarke County, Montana. W.} J. Sharwood. Coarser grains, about 5 mgm. each 828 143 0.173 Medium grains retained by 60-mesh sieve 820 158 0.193 ae CETONIET GOMER). 5.5 0 .cls 6a sce v0 g sesh eos 1 838 I51 0.182 Gold from cement or conglomerate of Black Hills) "fossil placers.'"" W. B. Devereux, Trans. A. I.| M. E., Vol. X., p. 465. oe RD pee So ES Se py Acre hock" 902 98 0.109 Pe Ff SPR ere CRAP e tree ceo: 803 107 0.12 EDs okes 3s 46.6.5. 5 0.05 S6s SSS SAAT SRE O17 83 0.09TS Pinos SHON ORIG Mie 5 ss Si NA ea es O15 85 0.093

retorting the amalgam, and also by the larger proportion of gold recovered by amalgamation as compared with that obtained by treating the tailings by the cyanide process. The coarser gold therefore is of higher " fineness," or contains a less proportion of silver—a condition the reverse of that noted in placers and agreeing with that recorded below in the case of the Homestake deposits.

F. B. Miller has noted a regional change in the silver-gold ratio of the gold of the eastern Australian provinces, the silver increasing northward from Victoria to Queensland,

St .,

ra

eS ee

Analyses Of Rocks From Homestake Mine. 781

original precipitation of the precious metals in different horizons. If such leaching took place to any considerable extent, samples gathered at horizons separated by several hundred feet ought to show appreciable differences in the ratio of gold to silver. Moreover the smaller particles of gold, exposing a relatively larger surface than the coarser grains, ought to lose rather more silver and show a lower silver-gold ratio. This condition has been reported as occurring in the placer gold of several localities. Ross Browne, Jr., and Hoffmann have described it in the case of the placer gold of Sierra County, California, and W. B. Devereux has noted it in the case of the " fossil placers" of the cement or conglomerate of the " Potsdam" ores of the Black Hills.

As a number of ore samples from various parts of the Homestake mine are panned daily for the purpose of estimating the free gold contents, it was an easy matter to obtain the accumulated pannings from different horizons. Several such series were saved and examined, and the results obtained with the most complete of them are summarized in Table II.

Table Iv.

Native GoLp FROM DIFFERENT Horizons, HoMESTAKE.

Horizon. No. Size of Grains. per per per Silver

eee eT - Surface ES EME DE o6: bnd tote 9:50.28 05. Vane. oho 5, bieleVedors! tre 831.0 169.0 , Trace 0.203 Workings 77, \|Medium (on roo-mesh) 823.0 177.0 Trace 0.215 98) PINE ATHFOUGN TOO). 60.6508 ee ce 819.5 176.2 4.3 0.215

and 600 80 |Medium (about 50-mesh) 832.0 163.0 5.0 0.196 Levels 8x |Medium (on 100-mesh) 829.0 163.0 8.0 0.197 82 ee REMrOUGH 200) 6 66 600865 540 823.0 173.3 ls eg 0.210

and 900 84 |Medium (on 100-mesh) 834.0 160.7 5.3 0.193 Levels 85 [Fine CERYOURD TOO) os .00.0.8 0 00 sue 830.0 167.5 3:8 0.202 S00 aiitli|'y Bb BE ie cites et antes oteiau a teed 847.0 158.8 0.2 0.189 Deeper 87 |Medium (on 100-mesh) 834.0 150.3 6.7 0.191 Levels 88 Fine CENSOUGN. TOO). vc ccccvecs 823.0 166.8 10.2 0.202! True average of all pannings. sseeeseeees 835.0 161.0 4.0 0.193

2 Total amount of this fraction was very small, making it difficult to clean and increasing the possible errors.

The samples examined constituted the entire pannings saved from daily tests in two weeks' work, those from different horizons being kept separate. The larger pieces were picked out, the remainder being separated (after washing as clean as possible) by sifting through a sieve of 100 meshes to the linear inch. Adhering quartz and sulphides were got rid of by boiling in hydrofluoric and dilute hydrochloric acids. The small amount of sulphide on the coarse pieces was scraped off, the finer lots were cleaned by amalgamating with pure mercury, cleaning the amalgam and rapidly expelling the mercury by heat. All assays were run with gold and silver proofs corresponding in weight and fineness.

The total "fineness" in precious metal of the coarser particles is remarkably high, the total base metal per 1,000 ranging only from a trace to 0.3—this including not only the copper, etc., which is actually alloyed with the gold but also any sulphide, quartz, etc., sticking to or enclosed in the gold, which may have been overlooked. The slightly lower fineness of the "medium" and "fine" particles may be partly due to unremoved impurities, but there is undoubtedly a larger proportion of silver to gold in the smaller particles. A blackish stain on some pieces of gold proved to be due to arsenopyrite; rio tellurium was found here or in the accompanying concentrates.

Table Iv 2.

AVERAGE OF ONE WEEK'S PANNINGS FROM ALL Parts OF MINE.'

No. Size of Grains. ' Gold. Silver hare} Ratio pig 89 |Very coarse (20 to 40 .) 839.5 157.8 2.7 0.188

92 Fine (between roo-and 200-mesh) .. 813.5 164.7 21.8 0.202 n ot clean) 93 Very fine (through 200-mesh) 797.0 161.0 42.0 0.202 n ot clean)

The extreme care taken in making these assays makes it improbable that the error should amount to more than 0.5 per 1,000

This was a preliminary series, the fractions not being as carefully cleaned as the foregoing.

Oq

Si

th

Analyses Of Rocks From Homestake Mine. 783

in the gold, or I in 1,000 of the silver. If, however, an error of as much as 2 parts per 1,000 should occur in each, and in opposite directions, the ratio would be affected only by 3 units in the third decimal place; thus, in the first item, if the values, instead of being 831 and 169, were 829 and 171 the ratio would become 0.206 instead of 0.203. Experimental error cannot therefore account for the considerable differences noted in these results.

From the 400-foot level downward, there is no general increase in the proportion of silver alloyed with the visible free gold. The silver ratio however certainly increases with the smallness of the particles.

In the surface workings from the 300-foot level upward, the assays of pannings indicate the remarkable condition of a higher proportion of silver to gold than in the unoxidized ore, which is contrary to the theory suggested by Mr. Emmons. A possible explanation lies in the fact that some of the ore from near the surface is of an essentially different character, and was probably affected by the same mineralization which produced the Cambrian ore, some of which overlies the Homestake ledge, and which contains silver in much larger proportions than the normal Homestake gold.

Assays of "refractory" or "siliceous" ore from the Cambrian strata partly overlying portions of the Homestake lode have shown a much larger proportion of silver, and there is abundant evidence of their being mineralized independently. For instance the average of 20 cars of selected ore, taken from these Cambrian deposits near the Homestake lode some years ago gave:

No. 94. Ounces per ton: Gold 1.00, Silver 8.33; ratio 8.33.

The ratios for individual cars ranged from 1.5 to 18.5, and the gold from 0.55 to 1.55 ounces per ton.

Out of a number of assays of samples from the Cambrian in the same vicinity the following may be cited as extremes:

Cambrian Siliceous Ores.

No. asana al besa Ratio Gold. Silver. °

It is quite possible that the solutions which mineralized these overlying strata may also to some extent have influenced the upper portions of the nearly vertical Homestake deposit.

Table V.

Native Gold From Different Ore-Zodies.

Base Metal Rati Silver

No. Gold per Silver per '° 1,000. per 1,000. ts) Highland ore body, upper levels: DD atl DAIEO 6 vn chs vis3.60 8 4 spose 830.0 165.5 4.5 (0.199)! 100 MMARINEL G veo scale' sea est bios 828.5 160.8 j; 10.7 0.194 Ty Se ee rrr k tT forte 822.0 158.0 20.0 0.192 Caledonia ore body, upper levels:! 102 OO SB RS ee sate 827.0 169.0 4.0 0.204 103 Medium and fine ! 818.0 T7158" JS0:8 0.210 104 (Coarse crystalline flakes from vug. 600 level, Fierce ore body 802.5 160.5 37.0? 0.200

Amount of coarse material available was too small to allow of sufficiently exact determination of this ratio.

*Some tellurium included here, owing to imperfect removal of adhering minerals.

A further comparison was made between pannings obtained from the Highland and the Caledonia ore-bodies, reserving only such samples as came from the upper levels of each. A sample was also examined of coarse flakes of crystalline gold, evidently the result of secondary concentration, found in a vugg lining, associated with calcite, quartz and a telluride (Fig. 418).

It is rarely possible to make direct comparisons from actual mill production, but at one period an opportunity occurred to segregate fully oxidized surface ore from the unoxidized in one

Analyses Of Rocks From Homestake Mine.

Ratios oF SILverR TO GOLD IN SOME ORE SAMPLES.

Ounces per Ton.

mill, and to sample separately the products results are given in Table VII.

in Amalgam. Gold

all the gold very fine: From copper plate in first row.! Gray unoxidized ore of average grade; part of the gold coarse:

From copper plate in first row.!

AMALGAMATION OF ORES oF Two TyYPEs.

Rata Sve Gold. Silver. Gold (EEE CS ES CG RET B'S) Ea ae a eee ieee are eras 6.40 1.72 0.27 |Caledonia open cut, average of 10 samples..| 0.47 0.27 0.575 |Caledonia open cut, average of 10 samples.. 0.72 0.36 0.500 |Average ratio of 20 samples — — 0.54

from each. The

Bullion Fineness.

Plain copper plates, no extraneous silver introduced here. High percentage indicates coarse grains of gold.

Silver.

Silver Gold*

Ratio

With the low-grade red ore less than 10 per cent. of the gold

was found in the mortars, and the amalgam from this source

"retorted" about the same percentage as that on the first copper plates, indicating the absence of any coarse gold. The ratio of

silver to gold was nearly the same in each case (.196 and .192) silver being low.

With the gray ore (in this particular case probably three times as rich as the red) one third of the gold was found in the mortars, and the amalgam from this source "retorted high" in precious metal, thus confirming the presence of a considerable proportion of coarse gold. The battery bullion, containing coarse gold, had a lower silver-gold ratio (0.224) than that from the

copper plate (0.242), indicating the presence of a larger proportion of silver in the finer particles of gold. Both these ratios are higher than in the case of the oxidized ore of the parallel mill run. This latter fact tends to confirm Mr. Emmons's contention that some silver has been leached out of the surface ore, but is not conclusive, as the two classes of ore came from two different sections. The difference in the silver-gold ratio of the two lots of amalgam from the gray ore confirms the results of Table IV., showing that the finer gold particles from any given zone contain a larger percentage of silver than the coarser grains. The total fineness in precious metal of the bullion from oxidized ore is lower than in that from the gray, indicating the presence of 1.9 to 2.2 per cent. of copper, etc., in the former bullion, as against 0.7 to 1.6 per cent. in the latter; this may be due to the presence of a little native copper in the oxidized surface ore.

General Conclusions as to Changes in Silver-Gold Ratio.

Consideration of the above data leads to the conclusion that changes which have been made in the principal metallurgical operation (amalgamation) are alone sufficient to explain the increase observable in the ratio of silver to gold. The introduction of electro-silvered plates corresponds with the sudden rise in this ratio for the period 1896-98, when an interval of little more than a year showed as great a change as the preceding ten or fifteen years. The slight general rise perceptible prior to 1896 is partly due to increase in the area of copper plates used in catching the gold, and probably in part to an actual change in the ratio in the ore treated. Since 1900 no decided upward tendency can be noted. Part of the general rise, and fluctuations, and also the variations between different mills, may be traced to variations in different ore-bodies, not necessarily to different horizons.

As regards the leaching effect which naturally tends to remove silver more rapidly than gold from the upper horizons, an examination of the isolated grains of native gold shows no such tendency; while there is little doubt that such leaching has occurred, the gold examined from the upper levels actually contained more

Analyses Of Rocks From Homestake Mine. 787

than the average proportion of silver—most probably owing to its being mineralized from a different source, which has thus masked any of the leaching effect anticipated by Emmons.

As the finer particles of visible free gold show more silver in proportion to the actual gold, and apparently more base metal, than is found in the coarser grains, it is very possible that the still finer particles of gold, non-amalgamable and invisible even with a microscope, but which are dissolved by a cyanide solution, may contain a still higher proportion of silver. Unless this is the case there must be some finely divided silver mineral present.

Since the ratio of silver to gold is slightly below 0.20 in the coarse grains, slightly higher in the fine visible particles, about the same in the gold caught by amalgamation in the mortars and the first copper plate, about 0.215 in the entire amalgamation product if we allow for silver introduced in the electro-plating, and about 0.43 in the cyanide product, it is probable that both these conditions exist, the cyanide obtaining part of the additional silver from very fine and invisible gold particles, and part from silver minerals occurring separately from the gold.

Summary.

Analyses of material from the Homestake mine include:

Trachytic Phonolite almost identical in composition with the pulaskose of Warren Peak, Wyoming.

Rhyolites with 68 to 71 per cent. silica, 14 per cent. alumina, and about 2 per cent. pyrite, but differing somewhat in the proportions of potash and soda. One type contains 12 per cent. potash, another about 3.6 per cent. soda and 6.4 per cent. potash.

Schists or slates with 50 to 66 per cent. silica and 12 to 16 per cent. alumina.

Mine waters containing bicarbonates of lime and magnesia, together with sulphates, the latter, as well as alkalis, being enormously increased in the case of water introduced into the workings after a fire.

One, the deepest flow met in the mine, contained little beside bicarbonate of soda. Normal surface waters differ in containing

the bicarbonates of lime and magnesia in rather less proportion than mine waters, together with a little silica, and with very small amounts of sodium compounds, chlorides and sulphates.

Chlorite with over 30 per cent. ferrous oxide, differing essentially in composition from recognized chlorites.

Cummingtonite, ferruginous hornblende agreeing closely in composition with the type mineral from Cummington, Mass.

Carbonates with widely varying proportions of calcium, magnesium, and iron.

Black mica with 27 per cent. ferrous and 6.8 per cent. ferric oxide.

Garnet, ferrous-alumina type.

Pyrite, arsenopyrite and pyrrhotite; the latter agreeing with the formula Fe,S,.

Quartz, belonging to several periods of deposition and varying greatly in purity and coarseness of grain.

Orthoclase, zircon, barite, hematite, magnetite, graphite, fluorite, galena, and a telluride of bismuth were identified, the two latter in a single occurrence: native copper, and a basic copper sulphate; black oxides of manganese.

Average lode matter, representing runs of many thousands of tons of ore of several types, and reflecting the high ferrous contents of prevailing minerals.

Native gold, practically free from base metal but containing silver in nearly constant proportions, approximating 0.20 silver to one of gold.

The ratio of silver to gold was carefully investigated, and proved to vary slightly in different ore bodies, for instance the Caledonia gold contains a little more silver than the Highland at about the same horizon. Some surface ore contains more, some slightly less, than the average proportion of silver to gold. Below the 300-foot level assays of panned gold show no appreciable change in the silver ratio with the greatest depths attained.

The coarser grains of gold contain relatively Jess silver than the finer visible particles. Assays of ore show the presence of

Analyses Of Rocks From Homestake Mine. 789

more silver than is normally alloyed with the gold contained. After removal of visible free gold and its alloyed silver by amalgamation, alkaline cyanide solutions dissolve further gold with a larger proportion of silver (Au: Ag==1:0.43). Hence some unrecognized silver mineral is probably present in a state of extremely fine division.

ORTHOCLASE-BEARING VEINS FROM RAWHIDE, NEVADA AND WEEHAWKEN, NEW JERSEY.

Austin F. Rocers,

Lindgren' was the first writer to emphasize the occurrence of orthoclase as a vein mineral. He describes the mineral from Silver City, Idaho,? and from Cripple Creek, Colorado.* Spurr mentions it from Tonopah, Nevada. Vein orthoclase has also been recorded from several localities in Germany, Austria, Norway, New Zealand and Mexico.

Large orthoclase crystals from veins in the Valenciana silver mine at Guanajuato, Mexico, were described by Breithaupt,® who gave the name valencianite to this variety on account of the abnormal angles.®° Lindgren suggests the name valencianite for vein orthoclase. Valencianite has the same habit as adularia, usually pseudorhombic with dominant and and often subordinate Valencianite is a better name to use for vein orthoclase than adularia for the orthoclase of veins is not usually clear and glassy like the typical adularia.

The object of this paper is to describe two occurrences of vein orthoclase, one a quartz-orthoclase replacement vein from Rawhide, Nevada, the other calcite-orthoclase fissure veins from Weehawken, New Jersey.

I. A Quartz-Orthoclase Vein From Rawhide, Nevada.

Among a suite of lavas and tuffs collected at Rawhide, Esmeralda County, Nevada, by Mr. H. W. Turner, mining engi-

20th An. Report U. S. G. S., part 3, p. 167, 1900.

Prof. Paper No. 54, U. S. G. S., p. 187, 1906.

'Prof. Paper No. 42, U. S. G. S., p. 86, 1905.

Schweigg. Jour., Bd. 60, p. 322, 1830.

*In the University collection there is a specimen of valencianite from Guanajuato. It consists of large (3 cm.) crystals which on account of the curved faces and pearly luster greatly resembles dolomite. The forms are and with very small faces of

Orthoclase-Bearing Veins. 791

neer and geologist, and presented to the geology department of Stanford University, there was found a peculiar quartz-orthoclase rock. This rock was called a dike in the field, but careful examination of a thin section proved it to be a vein. The hand specimen (No. 12) shows white, almost opaque, valencianite crystals (2 mm. in size) in a matrix of quartz. It looks something like an excessively silicified porphyritic rhyolite with the phenocrysts of orthoclase intact.

For notes on the occurrence of this vein and on the geology of the region I am indebted to Mr. E. C. Templeton, who made a study of the rocks and ore-deposits of Rawhide and obtained additional material for the University collections. Rock specimen No. 12 was collected from the surface above the tunnel on the Proske lease by Mr. Turner. Mr. Templeton could not find a rock identical with this but obtained somewhat similar

Fic. 427. Valencianite in silicified tuff (x 200). q—= quartz, v valencianite. material, evidently from the same vein, at a point fifty feet east of the Proske shaft on the southwest slope of Balloon Hill. Balloon Hill is capped by a rhyolite flow and surrounded on its lower flanks by a silicified rhyolite tuff or dacite tuff. The material described occurs as a single narrow vein up to 17 cm. in width. The vein cuts the silicified tuff, has a vertical attitude, and can be traced for only about fifteen feet. It is evidently a replacement vein rather than a true fissure vein for no comb structure, banding, or brecciation is apparent. It is not very

different from the tuff in appearance and the boundary between the two is not well marked.

The tuff is extensively silicified, consisting principally of secondary quartz and minute valencianite crystals (Fig. 427) with subordinate epidote in fine greenish-yellow aggregates. As the only original minerals are a few remnants of biotite, orthoclase, and plagioclase it is difficult to determine the original character of the tuff. It was probably rhyolitic or dacitic. A low power lens shows white or yellowish angular rock fragments in a rather clear ground-mass and some specimens show fragments of pumice and perlite in the slide. The tuff is usually massive but is sometimes banded white and gray or has a very fine texture.

The rhyolite capping Balloon Hill is a light grayish porphyritic rock showing flow structure. There are phenocrysts of quartz and sanidine but the ferro-magnesium minerals have apparently been replaced by secondary quartz. Secondary quartz is also prominent in the rhyolite and one specimen (No. 21 from Balloon-Mascot lease) contains minute crystals of valencianite which are also secondary.

The vein material consists essentially of quartz and valencianite. Some specimens contain cavities with small valencianite crystals of prismatic habit like Figtire 428 (an orthographic pro-ae

m b

mi ee oe So

Fic. 428. Valencianite. Fic. 429. Quartz.

prismatic quartz crystals terminated with the positive unit rhombohedron {1011} alone, were observed (Fig. 429). Thin sec-

Orthoclase-Bearing Veins. 793

tions of the vein material are represented by Figures 430 (No. 12) and 431 (No.2). The valencianite crystals have a rhombic crosssection with symmetrical extinction. The valencianite is rather

Fic. 430. Quartz-valencianite vein. g—= quartz, v=valencianite. ( X 40.)

Fic. 431. Quartz-valencianite vein.

cloudy, due to incipient alteration to both sericite and'kaolinite. Sericite in minute shreds with high order interference colors occurs in the centers of the crystals while towards the border there is an opaque white mineral which is probably kaolinite.

The valencianite is sometimes optically normal but in some crystals shows interesting optical anomalies. These crystals in polarized light are divided into four sectors which extinguish in diagonally opposite pairs. The extinction angle, measuring from the short diagonal is from 5° to 7° as shown in Fig. 432.

Fic. 432. FIG. 433. Fic. 434. Fic. 433. Valencianite bordered by albite. Fic. 434. Valencianite bordered by albite.

For these observations the large Fuess microscope with rotating nicols (No.VIa.) was used with excellent results. The view that orthoclase is triclinic but submicroscopically twinned receives some support from these observations.

Some of the valencianite crystals have a clear outer zone of albite in parallel position as illustrated by Fig. 433. The extinction angle, measuring from the short diagonal, varies from 8° to 15°, the maximum for albite in the zone [oor :100] being 16° The albite extinguishes in opposite pairs the same as the anomalous orthoclase. In other cases there is clear colorless albite on the exterior in parallel position as shown in Figure 434. At Kirebinsk in the Urals albite' is found in parallel position with adularia. Albite has also been found as a vein mineral in California, North Carolina, and Australia.

A partial analysis of the vein material (specimen No. 12, which contained no albite) made by Mr. H. F. Humphrey, assistant in mineralogy at Stanford University, gave the following results: K,O—4.10, Na,O=0.28. As the sericite and kaolinite are very trifling in amount it may be assumed that all of the alkalies are present in the feldspars. The analysis of the rock calculated from the percentages of the alkalies is as follows:

1 Hintze, " Handbuch der Mineralogie," Bd. II., p. 1466.

Orthoclase-Bearing Veins.

SiO. 90.70 Quartz 73.41 Al,Os 4.92 Valencianite 26.59 Na:O 0.28 100.00 K.0 4.10

This analysis is abnormally high in silica and low in alumina for an igneous rock. In Washington's Tables of Igneous Rocks? the highest silica percentage is 83.59 and only nine are above 80 per cent. The valencianite recalculated gives K,O— 15.48, Na,O=—1.04. A small soda percentage is characteristic of both valencianite and adularia and distinguishes them from other varieties of orthoclase.

The quartz occurs in the interlocking anhedra typical of vein quartz. It also shows optical anomalies. Between crossed nicols the quartz exhibits a radial structure with wavy extinction in sectors. Sections parallel to the c-axis, which are rather elongate and give the highest interference color for the

Fic. 435. Fic. 436.

slide extinguish in opposite quadrants, the extinction position in the two parts being only about 5° or 6° apart as represented in Fig. 435. Some sections are practically dark between crossed nicols and give a positive interference figure in convergent light. Irregular equidimensional sections, presumably slightly oblique to the c-axis, extinguish roughly in alternate sectors 30° apart,

1 Prof. Paper No. 14, U. S. G. S.

ideally represented by Fig. 436. It is difficult to interpret this optical behavior. Perhaps there are two interpenetrant parts, each occupying half of a dodecant and biaxial, but apparently uniaxial by superposition. Optically anomalous vein quartz from Cripple Creek has been described and figured by Lindgren.'

The only other minerals occurring in the vein are pyrite, in very small amounts and epidote in greenish-yellow aggregates. Mr. T. N. Turner, assistant in metallurgy at Stanford University. made an assay of the vein material and found 1.4 oz. of silver and 0.5 oz. of gold to the ton.

Ii. Calcite-Orthoclase Veins From Weehawken, New Jersey.

A number of years ago the writer collected specimens from veins in the diabase near Weehawken, New Jersey (on the Hudson River, opposite New York City). These veins are narrow, varying from 2 to6 cm. in width. They have a vertical attitude and are true fissure veins with banded structure and definite walls. The principal constituents of the veins are valencianite and calcite sometimes with quartz and with subordinate albite, pyrite, chalcopyrite, ilmenite, titanite, and apatite. Some of them contain valencianite with a narrow band of quartz in the

Fic. 437. Vein from Weehawken. valencianite, c—calcite, quartz, diabase. The small crosses represent pyrite crystals. center, while others have calcite in the center of the vein. The widest vein, illustrated by Fig. 437 (natural size), is 6 cm. wide and is more or less symmetrical. There is a narrow zone of valencianite nearest the walls and then a wide zone of cleavable calcite and in the center, valencianite and quartz. Pyrite is scattered all through the vein. Other veins are made up almost

1 Prof. Paper No. 54, U. S. G. S., p. 179, 1906, Fig. A, plate XVIII, and Fig. C, plate XVII.

Orthoclase-Bearing Veins. 797

entirely of a porous mass of valencianite crystals. Calcite has apparently been dissolved out of these specimens.

The valencianite of these veins is opaque flesh-colored like ordinary orthoclase in appearance but with the habit of adularia. The dominant forms are and with subordinate and sometimes The habit is short prismatic or

Fic. 438. Carlsbad twin of valencianite. c (001), x (101), m (110).

tabular parallel to +. The crystals are about 3 mm. in length. Penetration Carlsbad twins are common. Figure 438 is an orthographic projection of a twin.

In thin sections the valencianite is very cloudy, almost opaque. Albite is often present in spots in the valencianite and around .ts border. Lindgren noted a similar occurrence at Cripple Creek.? In a few cases albite occurred as independent crystals and was identified by the extinction angles of polysynthetic twins. The albite is clear and colorless and perhaps secondary. Several veins of almost pure albite in gray cloudy tabular crystals were observed.

The quartz in thin sections shows optical anomalies something like those described for the quartz from Rawhide, Nevada.

Pyrite occurs in octahedral crystals with subordinate pyritohedron and diploid {432}.

Chalcopyrite was noted in several specimens as small anhedra.

Ilmenite occurs in crystals with elongate cross-sections.

Titanite is prominent in some of the veins as well formed crystals with adamantine luster. It occurs intimately associated with ilmenite and also independently. This is perhaps the first record of titanite as a distinct vein mineral though it is common enough in clefts and seams of schists and gneisses.

Prof. Paper No. 54, U. S. G. S., p. 183, 1906.

Calcite occurs in large cleavable anhedra.

Chlorite is probably represented by a fibrous radiated yellowish green mineral.

A specimen from Bergen Hill, New Jersey, obtained from the Foote Mineral Company, shows the relation of these veins to datolite and the zeolites. A 2% cm. vein of reddish valencianite (Fig. 439) showing a little of the country-rock on each side had

Fic. 439. Section of vein from Weehawken (nat. size). valencianite, datolite, c—calcite, diabase.

been fractured (naturally) transversely across and crystallized datolite had been deposited on the fractured surface. A seam of datolite had also penetrated the vein showing clearly that the datolite and zeolites are later and probably independent of the period of vein formation. On another specimen of this kind crystals of apophyllite were found..

The diabase itself is probably the source of the vein materials. The titanium of the titanite and ilmenite is thus easily accounted for. Analyses! of the diabase of this region show K,O percentages varying from 0.39 to 2.10 and thus the. valencianite is accounted for.

Lindgren? accounts for the rarity of orthoclase in mineral veins by the abundance of carbon dioxid in thermal waters, saying that "under such conditions the more stable compound— muscovite or sericite—would be formed... ." This seenis reasonable as a general explanation but it fails in the case of the Weehawken occurrence, for in these veins the calcite must certainly have been deposited from carbonated waters. Moreower, the valencianite and calcite are usually intimately associated.

An. Report of the State Geologist of New Jersey for 1907, p. 121. 2 Am. Jour. Sci. (4), vol. 5, p. 420, 1808.

The Barite Deposits Near Five Islands, Nova Scotia.

CuHarLes H. WARREN.

It is the object of this paper to record briefly some observations made by the writer several years ago while on a visit to Nova Scotia,' relative to the mode of occurrence and probable origin of the barite deposits located near the village of Five Islands. This village is situated on the north shore of Minas Basin, an arm of the Bay of Fundy, about twelve miles east of Parsborro, the nearest large town, and opposite in a northeasterly direction from the celebrated Cape Blomidon. The bay just below the village, with its five, rugged, volcanic islands at the entrance and the high mass of Gerrish mountain to the eastward, forms what is justly considered one of the most picturesque spots in Nova Scotia.

Geology.—Triassic sediments with associated basalt flows from a narrow strip along the northern shore of Minas Basin to the eastward of Five Islands. At the village this strip is quite narrow and terminates along the shore a short distance to the westward. The relations of the sediments to the volcanics have been described and figured by Dawson in his " Acadian Geology." Few places are to be found where the characters of a lava flow and its relations to the underlying sediments are more beautifully shown than along the shore-line of Gerrish Mountain, itself a basaltic mass, and the chain of the Five Islands which are in fact the dissected remnants of a basaltic stream that ran from near the base of Gerrish Mountain to the westward over the Triassic sandstones. Other features of interest to the Geologist are: numerous vein-like segregations of magnetic iron-ore, often

*The writer here desires to express his thanks to Mr. A. R. Bayne, of

Boston, Mass., and Five Islands, N. S., for the opportunity of visiting this locality and for many courtesies received at his hands.

heavily charged with copper minerals, that lie in the basalt near its contact with the sediments; and numerous veins of gypsum traversing the sandstone in all directions.

Going north from the village, one comes in the course of about a mile into the edge of the Cobequid Hills, which extend in an easterly direction across this portion of Nova Scotia. A band of sediments are met with almost immediately on entering the hills which have been determined as Devonic but not subdivided by Fletcher.1 This band is here about a mile wide and extends with considerable variations in width for several miles to the east and west. The rocks are: slates, slatyquartzites, and quartzites of somewhat variable color and grain. At least one bed or lense of limestone occurs in them (on the west bank of the North River of Five Islands). Similar sediments occur more extensively developed further north and elsewhere in this range of hills. The core of the range appears to be composed of igneous rocks, chiefly a reddish syenite and darker colored dioritic rocks. These are intrusive into the devonic but not into later formations.

Several streams rise back in the hills, which here attain a height of about goo feet, and flow in a generally southerly direction to the Basin. Their channels lie between steep, rocky, and often precipitous banks until the streams pass out of the hills and wind across the recent gravels near the shore. Along the steep banks of one of these streams, known as the Bass River of Five Islands, where it cuts across the band of devonic sediments above referred to, some two miles north of the village, are located the principal deposits of barite with which this paper is concerned.

This particular band of sediments is characterized by steep dips, are often sharply folded and, in places, strongly faulted and brecciated. The fissures and brecciated portions are filled with a variety of minerals, chief among which are specular hematite, pyrite, chalcopyrite, limonite, ankerite, calcite and barite. There appears to be a more or less well defined line of major faulting and brecciation with subsequent mineralization, which extends

Report of the Canadian Geol. Survey, Vol. V., Pt. 2, 1890.

Barite Deposits Near Five Islands. 801

from a point somewhat west of the Bass River as far east as a point on the Great Village River north of Londonderry where it attains its greatest strength. According to Dawson ('' Acadian Geology") it can be traced for a distance of some seven miles and follows closely the general strike of the devonic strata at or near their contact with the igneous rocks. Dawson has furnished us with an interesting and picturesque description of the portion of the faulted zone as exposed on the Great Village River at the iron mines near Londonderry. The ore there is chiefly limonite and has evidently been derived from the alteration of ankerite which forms the cementing material of a fault breccia in the slate and quartzite. Barite also occurs lining fissures and as compact veins in the ankerite. Dawson and also Fletcher have expressed the opinion that the barite on the Bass River as well as that on the East River of Five Islands, lies on the same zone of faulting.

The Bass River Deposit—The occurrence of barite here is first mentioned in Howe's " Mineralogy," published during the early part of the last century. Since then they have been referred to by Dawson and Fletcher and still more recently they have been briefly described by Mr. H. Spencer Hutchinson,' a mining engineer of Boston. The mineral appears to have been mined on quite an extensive scale some 60 years ago and intermittently since then, although serious trouble with the titles caused abandonment of operations until recently. The property is now in a position to resume active mining operations.

Measured north and south along the river the principal outcrops of the barite occur within a zone estimated to be about 300 yards, although beyond this zone to the north there are said to be several showings of the mineral for 34 of a mile. The richest showings at present lie on the western bank of the river which rises at this point to a height of from 200 to 300 ft. above the bed of the stream. Some strong veins have been exposed on the eastern bank which is much lower in the immediate vicinity of the river rising, however, to a height corresponding to that of the western bank at a somewhat greater distance from the river.

Mineral Industry," 1907.

The barite occurs first, in the form of veins and masses of greatly varying size enclosed in what at first sight, appears to be nothing but talus or drift lying in the depressions between rocky ledges or shoulders on the steep (30 degrees) banks of the river; and secondly, filling large and small fissures and brecciated zones in the devonic slates and slaty quartzites or quartzites. A closer inspection of the enclosing material of the first-mentioned mode of occurrence, shows that it consists of angular fragments of the rocks found in the immediate ledges, held in a matrix consisting of finer material of the same character. The whole mass has been quite thoroughly leached by solutions but is now rather firmly cemented by a calcareous and siliceous cement. Many of the fragments, which vary in size from mere grains up to pieces a yard or more in diameter, have been reduced to a light colored, putty-like material. Such appear to have been originally slate. Others, originally quartzite, are harder but still thoroughly leached ; other fragments show dendrite stains. In one place at least, this enclosing material appeared to pass gradually into the brecciated but unaltered country rock; again it seems to lie upon the solid ledge. The writer reached the conclusion that this material represents a modified, ancient fault breccia more or less mingled superficially with surface detritus.

Through this material the barite is found in the form of irregular veins and detached masses. The latter vary in size from nodules as large as one's fist up to masses a foot or two in their largest dimension. The veins vary from 3" to 3 or 4 ft., or in places where two veins coalesce, a thickness of 6 to 8 ft. may be seen. Several veins may be followed in the old tunnels for 50 or 60 ft. in length without pinching out and it appears that some veins were followed for much greater distances in some of the old workings. Their course is more or less irregular, but the general trend is highly inclined.

The barite of these veins or masses is remarkably pure and uniform in character and throughout is of the massive crystalline type, consisting of closely packed, tabular crystal plates from %" to %" in thickness and often several inches in length and

Barite Deposits Near Five Islands. 803

breadth. The plates are commonly arranged with a slightly divergent habit forming groups or clusters. Open spaces are common, and in these, freely developed tabular crystals of great beauty and complexity of form are developed. The points from which the crystallization of the groups started are quite irregular, sometimes being near the margin, again near the center, and their growth seems to have determined the irregular outer surfaces of the veins and masses. The growth of the veins evidently took place along a general line of deposition, the crystallization beginning at innumerable points. In the pockets are often found crystallizations of calcite, the habit of the crystals suggesting that of the well-known crystals from Joplin, Mo. The prevailing color of the barite is white, grading into a pale yellow or becoming nearly colorless in some of the pockets. In the massive portions an occasional reddish stain may be seen. 'This seems to be due to the oxidation of minute grains of pyrite or chalcopyrite, minute specks of which may sometimes be seen in the barite. The total amount of impurity even in the crude mineral is small, insignificant from a commercial point of view. An analysis, made on a sample of unsorted material taken from an ore bin is given by Mr. Hutchinson (Joc. cit.) and is as follows:

Seep ward ites sampler ake sale ewe pepletlh ea eataleneetens 08.54 10 SE SCE MORI She none 95 AlO; bWk sh 6. © 0. 0.0/8 8: 0.b 410.68: 6,8 50.68 /4.0:8,040,5,670 0050.8 CO ee a 6 ae ee .02 ad heise ahs bce ete de cee COMEN te ble Koco eee 22 aig es tan beuieh eter aehen Bares lees ed tie ata eet 02 FeS: TrCerrer er ere ee Tee ke ee re ee ee a ee .07 1 0) Se a Rell a ete OR eae Smee Me a RN ha Saree iia 15

In at least one place near to southern edge of the barite-rich zone these veins may be followed directly down into a fissure or broken zone in the slate and this relation to the country rock is doubtless a general one. The vein in the slate at this point deserves particular notice. It has been uncovered for a distance of some forty feet, with a width of about twenty. It lies in the slate quite near to the river and follows a fissure or broken zone

in the fresh unaltered slate rock. To the south it passes underneath a rocky shoulder and is thought to have been again met with some few yards on the other side. To the north its extent is still unknown. The filling of the fissure consists of barite and perfectly angular fragments of slate like the walls. The barite is exactly like that above described and constitutes something over one-half by volume of the whole. The slate fragments vary in size from mere grains up to fragments two feet through. Their edges and corners are perfectly sharp and the slate shows no evidence of solution or alteration.

The barium bearing solutions apparently followed along a broken streak in the slate depositing the mineral between the fragments, gradually forcing them apart as it grew and so enlarging the fissure. That the slate fragments can represent residual material and that the barite has replaced the slate by solution seems hardly possible in view of the angular and perfectly fresh character of the enclosed fragments. Small stringers of barite also branch off from the main mass and run out into the surrounding slate.

At another point a little to the north and well up toward the top of the cliff another large fissure may be seen in the slatyquartzite. This is some six feet in width and of unknown depth and was entirely filled with barite. The mineral has been mined out for some fifty feet into the hill but fragments or it may still be seen on the walls and a solid face of mineral is said to be still standing at the back of the tunnel. As to how far those veins extend with depth cannot be determined from any data at hand but the strength of the larger veins referred to gives promise of considerable depth. The numerous outcrops of barite clear to the top of the slope and beyond it on the western side of the stream, also the outcroppings on the eastern side, all point to the presence of other fissures than those to be actually seen in the underlying rock.

Deposits to the East of the Bass River—Going east from the river, barite outcrops at various points in the soil and in exposed ledges. Some of these have in fact been worked by the in-

Barite Deposits Near Five Islands. 805

habitants in the past and considerable barite has undoubtedly been taken out. The outcrops seem to be more or less numerous for a distance of about two miles, or as far as the East River of Five Islands. At one point on the banks of this stream where a bold ledge of reddish quartzite occurs, barite may be seen filling numerous small fissures and cracks in the quartzite. Somewhat further down the stream on the eastern side, a vein of considerable size occurs. This is exposed in an old tunnel for about fifty feet. One wall is well defined, the other is more or less broken, and irregular and fragments of the greenish, slaty wall-rock are enclosed in the barite. The character of the mineral is much the same as that previously described.

Origin of the Barite——It seems improbable to the writer that the barite has resulted from deposition by hot waters arising from deep-seated sources. The sudden cooling and relief of pressure that would be likely to accompany the escape of such solutions into open fissures or brecciated rock material, would be more likely to produce a fine-grained or compact, barytic sinter than the coarsely crystalline material here met with. The coarse crystalline structure in the present instance seems to argue in favor of a slow deposition from circulating vadose waters which derived their barium content from the surrounding or overlying rocks.

A short glance at the published analyses of sandstones, shales, etc., shows that the barium is generally, if not always, present in small amount and sometimes in notable quantities. Thus Dr. Clark! gives a composite analysis of 253 sandstones by H. N. Stokes showing BaO, 0.05 per cent.; of 51 paleozoic shales showing BaO, 0.04 per cent.; of 27 mesozoic shales showing BaO, 0.06 per cent.; of middle cambrian shale showing BaQO, 0.06 per cent.; and of several roofing slates showing BaO, 0.04 to 0.08 per cent. A chemical analysis by the author of a specimen of quartzite and of fresh black slate, both selected at a distance from any visible barite from the ledges on the Bass River, gave BaO, 0.18 per cent. (BaSO,, 0.27 per cent.) and BaO,

Bull. U.-S.G2S.,tNo..430:

0.08 per cent. (BaSO,, 0.13 per cent.) respectively. These figures are in agreement with those cited from other sources. It is of course possible that the barium content of other portions of these rocks may be considerably higher, for sandstones are known in which a considerable portion of the cementing material consists of barium sulphate.?

The per cent. of barium shown to be present in the enclosing and adjacent rocks could serve as a source of barium for the veins if a sufficiently large volume of the rocks were leached. The crudest kind of an estimate based on the per cent. of barium present in the samples analyzed and the amount of leached, fragmental or altered rock material at present associated with the barite deposits on the immediate banks of the Bass River makes it quite certain that these alone are quite incompetent to have furnished more than a small portion of the mineral now in the deposit. We must therefore look for the supply of barium either in an upward extension of the faulted and brecciated zone, now removed by erosion, or in extensive portions of the more massive parts of the devonic rocks and perhaps to other strata now wholly removed. Among such strata it seems not unlikely that carbonate rocks formed a part. Indeed, the large quantities of ankerite found in the eastern part Of the fault-zone rather lends support to that view that carbonate rocks were to some extent concerned in furnishing the minerals found in the zone.

The exact method of solution of the barium and its deposition must be in the present case largely conjectural. If, however, the barium was collected by the leaching action of vadose waters acting on the surrounding or overlying rock-material it does not appear probable that the barium could have been dissolved out as barium sulphate to be deposited again at greater depths where presumably the solubility of the salt would have been greater on account of the higher temperatures. It is more reasonable to suppose, as has been suggested by several authors for other deposits, that the barium was originally dissolved as bicarbonate and, mingling with sulphate-bearing waters, reacted at greater

*See F. Clowes, Proceedings Roy. Soc., vol. 46, p. 363, 1889.

Barite Deposits Near Five Islands. 807

depths to form barium sulphate which thereupon crystallized along lines of flowage.

A brief examination of the somewhat scanty sources of information relative to barite deposits shows that there is a general similarity, and indeed, in some instances a very close similarity, between the Five Island deposits and those of certain other localities.1 The enclosing wall-rocks appear to be sandstone, quartzite slates or limestones and the barite occurs either in fissures, along fault zones, contact planes, or as residual replacements of the rock itself along fissures and cracks. On the whole there seems to be little doubt that barite deposits, other than those definitely connected with metallic deposits of magmatic origin, have been formed by deposition along fissures or brecciated zones from vadose waters which derived their barium content from the surrounding or overlying formations.

*Among the deposits particularly in mind in this connection are: those of Richlands, Tazwell Co., Va. (" Mineral Industry," 1908; Waynesboro, Pa. (Bull. U. S. G. S., No. 225, p. 515); Cheshire, Conn.; and several other deposits in other parts of Nova Scotia and Cape Breton. The latter are not described in the literature and are known to the writer only through accounts given by parties who have visited them.)

Discussion

This department has been established by the editors in order to afford to those interested in questions. relating to economic geology an opportunity for informal discuss'on. Contributions are cordially invited either in the form of discussion of more formal papers appearing in earlier numbers or bearing upon matters not previously treated. Letters should be directed to the Editor, Sheffield Scientific School of Yale University, New Haven, Conn. The full name of the author should be attached to all communications.

Additional Factors In The Origin And Accumulation Of Oil.

Sir: In reading the very interesting and welcome historical article by M. R. Campbell on the "Origin and Accumulation of Oil" in the Economic Geotocy for August, 1911, I have noticed the following omissions as to recent contributions, apparently overlooked by the author.

1. The deviations from horizontality of the reservoir from other reasons than deformation. R. S. Blatchley in Bull. No. 16 Ill. Geol. Survey states, "Some question has arisen as to whether these minor arches are true anticlines of deformational character or whether they represent merely thickening or thinning of particular beds or, again, whether they result from unequal settling during the consolidation of the sediments. Locally any or all of these factors may account for the conditions." My own experience in the Mid-Continent Field convinces me that much of the structure of our oil-bearing sands is to be attributed to these causes, rather than true deformation.

2. The importance of the extension of the anticlinal theory to monoclinal conditions is not adequately brought out. The anticlinal theory as here discussed overlooks for the main part the great importance of the very common limitation in size of the reservoir so that it fails to reach the crests of either anticline or syncline and the existence of such pools in monoclines where there is no significant arrest. Griswold and Munn seem to have

Discussion. 809

been the first to definitely formulate this principle. '' Where the area of porous rocks is limited the accumulation will occur at the highest point of the porous stratum (where saturation prevails)." The importance of this limitation was dwelt upon in my "Methods of Prospecting, Development and Appraisement in the Mid-Continent Field" in the Oil and Gas Journal, Feb. 20, 1910, and it has been formally added by Clapp to his classification in the Oil and Gas Journal for April 27, 1911, as " Monoclinal dips. Where the accumulations are due to thinning out or change in texture of the sand in some direction."

3. The fact that this "thinning out or change in texture" is not hap-hazard and therefore that the shape of the body of the oil-bearing sand shows some degree of regularity in any one horizon and district. This becomes a matter of practical importance in those horizons where the bodies of sand capable of bearing oil have predominantly an elongate shape, especially common in the Mid-Continent Field. In order to emphasize the importance of shape I have suggested that the term sand-body be adopted, from the analogy of the word ore-body, to describe the reservoir, 1. ¢., continuous mass of sand or sandstones sufficiently porous to be capable of containing oil and gas in commercial quantities regardless of whether it contains gas, oil, water or air in its several parts. While from incomplete data very many elongate (more or less irregular to be sure) sand bodies may be cited in the Mid-Continent Field I have sufficient records to show that the oil pool crossing the eastern ends of Osage lots 62 to 68 is elongate because of the shape of its sand body rather than because of any deformation. In this case the limiting lateral dry holes are not water or gas wells but are dry because the productive sand is " pinched out." In my article cited above there is a discussion of the practical importance to the prospector of learning these "trends" as well as the deformation, and also a discussion of the consequence of the meeting of one of these "streaks" and an anticline at an angle. The tendency to assume that an elongate pool is as a matter of course anticlinal, should, be guarded against, especially in the Mid-Continent Field. Different

sand horizons have sand bodies of different prevailing shapes and the skill of the prospector lies largely in recognizing these peculiarities. American geologists have lagged behind the Europeans who have used this knowledge effectively at Pechelbronn in Alsace, as shown in Engler and Héfer's " Das Erdol," pp. 219-220.

4. This opportunity is taken to add some suggestions as to the role of barrier beaches and salt marshes in the origin and accumulation of oil. The south shore of Long Island is very low and edged with sedgy marshes. For a long distance a barrier beach of sand similar in texture to our best oil sands lies from one to three miles from the shore. The intervening lagoon communicates at occasional inlets with the ocean. It supports a rich flora of eel grass and alge and an accompanying fauna. The resulting deposits are black and gray muds and clay, often odorous with the decay of plants and animals. The conditions are just such as would be expected to produce elongate sand bodies, contiguous to organic shales.

In the event of such a shore subsiding, the beach would leave a bed of sand extending in over the lagoon muds and covered by offshore deposits. With a regular shore line and a suitably paced subsidence the march would be so regular as to leave a relatively uniform sandstone bed. In the event of a more irregular subsidence the barrier beach built up on the lagoon muds would occasionally be caught as pod-shaped sand bodies in the shales. Offshore bars and "spits" carried out past points as at Sandy Hook and Cape Cod or swinging across the mouth of bays would also contribute sand bodies of more or less elongate shape where not later worked over by wave action. Where tide inlets cut across such structures there is interruption with the misplaced sand often more thoroughly graded than on the shore proper and thrown out in fans laterally. Many of the irregularities of oil sands including small areas of unusual coarseness may be attributed to such causes.

There is a long shore-line having barrier beaches and included lagoons, as may be observed by following the shore on a good map, say from Portland to Key West. But it is not only these

Discussion. 811

types of sand deposits which are significant but their associations with the muds of the lagoons rich in organic remains.

C. B. Morrey (Geol. Survey, Ohio (4) Bull. 1, p. 313) has referred to the role of bacteria in organic decay and hence in the origin of oil. He fails, however, to distinguish between the following types of bacterial decay, a distinction which is all important in this connection.

(a) Sub-trial decay. The bacterial flora here accomplishes so complete an oxidation that there is a minimum of coal or oil formed. The carbon is largely dissipated.

(b) Fresh water decay. The bacterial flora here also oxidizes so actively that only limy deposits remain, giving us marl.

(c) Bog-water decay. The action by the bacterial flora in this case is such that while there is some formation of methane (marsh gas) the plant remains are in large part not oxidized, but preserved as peat, lignite, or coal.

(d) Salt-water decay. The bacterial flora in this case while more actively oxidizing animal materials affects plant remains in such a way that there is less methane formed and the heavier hydrocarbons (oil) rather than coal are formed, not as a direct immediate result, but as an ultimate one.

One hesitates to offer any additional unsupported ideas in this theory-rich and data-poor field. I can only urge the bacteriologist and bio-chemist to investigate decay in salt water. The distillation experiments seem to have been always on fresh animal or vegetable tissues. The geologist has reached a point where the bordering sciences must lend a hand. However, we need still more a physicist to investigate the dynamic interaction of oil and salt water in sandstones and shales.

River Sands.

The Chester Hill pool mapped by Bownocker in the Geol. Survey, Ohio (4) Bull. 1, p. 128, is so extremely sinuous in its shape as to apparently preclude beach action and to suggest a river deposit which escaped the usual "working over" in the advancing shore, by a rapid subsidence.

Roswett H. JoHNnson.

Sir: In an article, entitled " Historical Review of Theories by American Geologists to account for the Origin and Accumulation of Oil," which appeared in Economic Grotocy, Volume VI., No. 4 (p. 379), I made the following statement :

"This limiting condition is found in moisture in fine-grained rock, but to whom should be given the credit of the discovery the writer does not know. Day doubtless observed it, but failed to state it in any of his publications."

Recently my attention has been called to a paper by Day in The Transactions of the American Institute of Mining Engineers (Vol. XLI., pp. 219-224), in which he states clearly that moist clay and other fine-grained rocks are impervious to oil. The quotation given above agreed, as I supposed, with Day's oral statement, but evidently I misunderstood him, and, for the time being, had lost sight of his paper read before the American Institute. To David T. Day, therefore, belongs the credit of the discovery of one of the conditions which may have affected the accumulation of oil.

M. R. Campbell.

Reviews

The Natural History of Coal. By E. A. Newert Arper, M.A., F.LS., F.G.S., Trinity College, Cambridge. Cambridge Univ. Press, 1911, pp. 163.

The publication of this booklet, written in untechnical language is an index of the popular interest in the subject treated. The present work comprehends discussions of the various aspects of the formation of coal, including the deposition of peat and the conversion of the original "mother substance" into coals of different kinds. To cover so wide a field the presentation must necessarily be brief.

The formation of coal has been the subject of so manv theories that it is difficult to invent a new one. Practically all the basic patents were issued perhaps a generation or more ago, so that for the students of the present day there is little left except to search for valid specifications. Slight amendments, new and important applications of some of the early ideas, and, above all, the real demonstration of an idea, are perhaps the best that can be hoped for. Unlike most of his predecessors, Mr. Arber has largely contented himself with summarizing the opinions of others rather than expounding any new theories or enforcing his personal views. On some of the mooted questions it is slightly difficult to determine what he really thinks, possibly because he is awaiting further evidence. In a few cases, however, he does not take cognizance of all the facts at present available.

Like most British writers, Arber appears, in describing the conditions of the formation of peat, to have centrally in mind the bogs of Great Britain and the North Temperate Zone, in which the topographic and climatic conditions are, geologically speaking, abnormal and widely variant from those prevailing during the deposition of the broadly extended coal fields of the earth. Some peat students may not agree with him that "the occurrence of peat depends not only on the prevalence of particular climatic conditions, but also on the existence of a special type of vegetation in the district." It is interesting, too, to note that in citing Lyell's and Shaler's descriptions of the Dismal Swamp he refers to the "soil" of that swamp, which he does not appear to regard as a peat. This "soil," he seems to think, contains very little megascopic vegetable debris, whereas, in fact, the logs and stumps in it are so

numerous that it is difficult to ram a steel rod down to a depth of 6 feet.

The statement that "the Tertiary lignites consist chiefly of Angiospermous woods" is quite at variance with the observations in this country, where the carbonized woods in the Tertiary lignites of North Dakota, Montana, Arkansas, and Texas, and in the Cretaceous of the Coastal Plain series are found to be dominantly Gymnospermous. The autochthonous, or growth-in-place, theory for the accumulation of the vegetable debris in the coals is accepted by Arber for most regions and most coals of the ordinary or humic type, though he appears to discredit the evidence of the erect position of the stumps found in the roofs of coal beds as valid proof in general of their growth in place. Regarding this point the reviewer, without citing other lines of evidence, is constrained to remark that only in the rarest circumstances could the water immediately following the submergence of an autochthonous peat have been deep enough to float large trees in an upright position over the area of normally thick peat.

The theory of transformation of peat to coals of different grades through the agency of pressure-metamorphism is discussed by Arber, who, however, while admitting that it may have happened in many cases, is, on the whole, disposed to believe that the question of whether the mother substance should become anthracite, bituminous, or coal of other grades, may have been largely predestined in the early stages of the coal-forming process, namely, in the conditions of deposition and the kinds of plants contributed. Thus, he says " The nature of the vegetation undoubtedly determines the character of the product, and Paleozoic plants were almost entirely distinct from those which contributed to the bulk of any modern fuel." In leaning toward the explanation that anthracite and other high grade coals owe their quality to peculiar kinds of vegetation, an attitude remarkable for a paleobotanist, Professor Arber seems to be influenced by the conclusions of Strahan and Pollard, as set forth in their discussion of the analyses of the coals of the South Wales coal field, reviewed in No. 3, Vol. IV., of this journal. The point of view of the author is, however, fully explained in his statement (p. 69) "If the peat-to-anthracite theory holds, it is curious that we find no true humic or anthracite coals in the Cretaceous or Tertiary period." He seems to lose sight of the facts (1) that coals of the highest grades do occur in the Tertiary and Cretaceous, and in relatively large and important areas; (2) that the essential 'constituents of plant tissues are the same in all periods—the carbohydrates, fats, resins, waxes, etc., contained in the ancient plants are not essentially different from those of the plant living today; and (3) that in the same formations coals of the same vegetable origin are found in the western Cretaceous and Tertiary of the United States to pass, as the result of regional metamorphism,

co — me — 45 45 Fe oe CU lUlCU,

ao fr wn A Ww

a2 H+ 7A OO oF

es a © fe

Reviews. 815

from lignites or subbituminous coals into bituminous coals of high grade, and in some instances even to anthracites.

The algal nature of the vegetable remains characteristic of the kerosene shales and bogheads, and described by Renault and Bertrand as Reinschia and Pila, is accepted by Arber, who notes, however, Jeffrey's argument that they are spores rather than alge. In this connection the reviewer digresses to point out that the question at issue is mainly a botanical one, although naturally it concerns also the chemical changes undergone by the organic ingredient materials, a subject on which we are still in profoundly deep darkness, where we will remain until the highly varied and numerous hydrocarbon combinations actually existing in the different coals themselves shall have been determined. Economic-. ally the essential point is that these bodies, whether alge or spores, unmistakably impart special and very important characters to the coals in which they occur, these characters being very distinct when the bodies predominate in the substance of the coal.

The booklet is illustrated by about two dozen figures, relating mainly to the types of plants and the conditions of their occurrence. Additional illustrations showing actual microscopical sections of coals, other. than bogheads, would have greatly enhanced the interest of the work.

In critically reviewing a work of such necessary brevity on a subject so broad and complicated, it is easy to dwell on its faults or on differences of opinion, and so to lose sight of the valuable service of con- Scientiously compiling from the voluminous literature a well-proportioned statement of ascertained fact differentiated from mere testimony and clever but conflicting arguments.

Davip WHITE.

Coal Resources of Iowa. Iowa State Geol. Surv., Vol. XIX. Annual

Report, 1908, with accompanying papers.

The Coal Resources of Iowa is the real subject of the 19th volume of the reports of the Geological Survey of Iowa, for the greater part of its 800 pages is given to the economic geology, analyses, and tests of the coals and peats in the State. A short introductory chapter by S. W. Beyer on the Mineral Production of Iowa fer 1908, very fitly heads the volume.

In Iowa the coal field, which extends through twenty-three or more counties, is estimated to cover 19,000 square miles, not counting areas overlain by the Cretaceous or by the higher, and practically barren, marine series known as the Missourian. Two-thirds of the area is rated as potentially productive. With the exception of a small area in the Missourian in the southwestern part of the State, the workable coals

are confined to the Des Moines series in the lower divisions of the Pennsylvanian. This is divided into the (basal) Cherokee formation of shales, sandstones, clays, thin local limestones, and coals, not exceeding 500 feet in thickness, which is capped by a formation, apparently less than 150 feet thick, known as the Appanoose Henrietta of Missouri), mainly composed of limestones. This formation, unlike the Cherokee, was laid down on an even floor and at a widely extended water level. Its strata, including the Mystic coal, are conspicuous for their regular bedding over a large area. The Pleasanton formation, chiefly shales and sandstones, in all less than 200 feet in thickness, and carrying several very thin coals, tops the Des Moines. Most of the coal mined in Iowa, which ranks ninth among the states in production, comes from the Cherokee shales, chiefly their lower part,—that is, from beds of Upper Pottsville and Lower Allegheny age.

In late Pottsville time the Pennsylvania sea, invading the Iowa region, covered a fairly well developed topographic relief; consequently the lower beds of the series are mostly confined to the valleys and hollows of the old surface. In these very irregular and restricted depressions the coals were sometimes laid down close together, and, though often of considerable thickness locally, they are lenticular and disconnected, as well as highly variable in stratigraphic interval. Almost invariably they thicken down the slopes of the basins, frequently disappearing wholly on the rises. Comparatively few of these basins are known to contain over a thousand acres; most of them probably carry workable coal under less than 500 acres. The shales and sandstones, as well as the coals of the basal Cherokee, vary extraordinarily and are often horizontally intergraded, so that within short distances it is frequently impossible to identify sandstones or coals, either in drill records or outcrops. The variability of the beds, and the generally thick covering of the drift, averaging over 100 feet through most of the coal field, render correlation of the lower coals practically impossible. They also necessitate very close drilling and consequent large expense. The result is that most of the mines in the State are on or near the water courses where the coal measures are exposed or :sily reached, though undoubtedly these regions are not richer tha:: the extensive intermediate areas which, for the reasons just stated, have remained almost untested.

The thickest coals of the State are the lenticular beds, sometimes but a few feet apart, in the lower portion of the Cherokee in the " basins," where they are said to be worked usually in thicknesses of from 4 to 6 feet, the maximum being found in a lens 16 feet thick in Marion County. Here the coal is rather impure. Mining, however, is often continued, especially for local use, in beds much thinner; and the Mystic coal (in the Appanoose formation) which, like its accompanying limestones, is

Reviews. 517

remarkably regular in thickness, bedding, and extent, being known over at least 275,000 acres within the limits of the State, furnishes a large production (16 per cent.) from a thickness approaching 30 inches. The thin coal in the Missourian of Taylor, Page, and Adams counties, is said to have been mined in Nodaway County, Missouri, at a thickness of 12 inches. Most of the mines in Iowa are very shallow, the deepest being 315 feet.

The descriptive part of the report, embracing about 400 pages, by Henry Hinds, treats the economic geology of the coal field. Within the county unit each basin is discussed with reference to exposures of the beds, number and thickness of coals, stratigraphic sections, developments, mining conditions, equipment, and methods, etc. The data relating to several counties is, unfortunately, largely compiled. In view of the fact that this paper is early work the results are most creditable. Criticism, if made, might touch upon a lack of detailed description of the physical characters and structure of the coal itself as mined or in the bed.

Following the economic description of the coal field are short chapters giving the results of the tests, chemical and otherwise, of Iowa coals in the laboratories of the U. S. Geological Survey at the St. Louis Exposition, and presenting an excellent review, by James H. Lees and A. W. Hixon, of the chemical analyses of a large number of Iowa coals, representing nearly every coal-producing county in the State, as reported by various analysts. As might be expected, the greater number of the analyses are not accompanied by calorimetric determinations. Mr. T. E. Savage points out that the average sulphur of the Iowa coals tested at St. Louis is 4.67 per cent.; the average calorific value 6,144 calories (11,066 B. t. u.'s); and the amount of coal required in the producergas test to generate one electric horse-power-hour is 1.75 pounds, whereas the same work required 4.95 pounds under the boiler. The coal used for the producer-gas test contained 17 per cent. of ash.

The geographic and economic descriptions of the peat deposits of Iowa, by S. W. Beyer, accompanied by about 300 proximate analyses, mostly with calorimetric determinations, appropriately forms a part of a volume on the coal resources of the State. This chapter is supplemented by an article of 50 pages by Professor Pammel on the flora of the northern Iowa peat bogs. Other chapters germane to the general subject include an excellent History of Coal Mining in Iowa, with a bibliography of the literature on Iowa coals by James H. Lees, and the Stratigraphy of the Missourian Coal Measures by G. L. Smith.

Davip Wuite.

Scientific Notes And News'

D. F. McDona_p, geologist of the Isthmian Canal Commission, is in Washington and Boston on furlough from his work in the Canal Zone.

Hoyt S. GALE, of the U. S. Geological Survey, left Washington the first of January to visit the survey's deep drilling test at Fallon, Nevada, where an attempt is being made to find a deposit of potash salts, and subsequently will go to Portland, Oregon, and Coeur d'Alene, Idaho.

E. S. BAsTINn returned to Washington the middle of December after completing the field work on the geology of Gilpin County, Colorado, and adjacent areas. He was assisted in the -work by J. M. Hill, of Washington, and C. W. Henderson, of Denver.

G. C. Matson has returned to Washington after spending the summer in an investigation of the Upper Tertiary of the Gulf Coastal Plain in southwestern Mississippi and southern Louisiana. :

R. W. Pack returned to Washington, January 4, from California, where he has been for several months studying the Kern River oil field.

How.anp Bancrort, of the U. S. Geological Survey, who spent the past summer in an extensive trip. through Peru, Bolivia and Chile, examining mining properties, expects to go to Colorado the latter part of January.

Ort and gas men will be interested in the announcement that the U. S. Geological Survey has in press a bulletin, No. 4714, containing the following papers: The Campton Oil Field, Ken-

Geologists, mining engineers and others interested in applied geology are invited to keep the editor informed of new investigations of mining districts or scientific studies undertaken by them, together with such other scientific and personal items as may come to their notice.

Scientific Notes And News. 819

tucky, Oil and Gas Development in Knox County, Kentucky, The Fayette Gas Field, Alabama, by M. J. Munn; The Powder River Oil Field, Wyoming, by C. H. Wegemann; Geology of the San Juan Oil Field, Utah, by E. G. Woodruff; Notes on the Geology and Possible Oil Resources of the South End of the San Joaquin Valley, California, by Robert Anderson.

PRELIMINARY figures of the Director of the Mint indicate a domestic gold output of $96,233,528 in 1911, against $96,269,100 in 1910, and a domestic production of silver in 1911 of $31,787,- 866 against $30,854,500 in IgIO.

Dr. Davip T. Day, of the U. S. Geological Survey, has gone to Vienna, Austria, to attend the meeting of the International Commission of Petroleum Testing Methods.

Mr. Horace WINCHELL lectured to the Geology Club of the University of Minnesota, December 7, on "The Secondary Enrichment of Ore Deposits."

J. E. Spurr has accepted the position of Vice-president in Charge of Mining and Advising Engineer for the Tonopah Mining Company of Nevada. His new offices will be in Philadelphia at 571 Bullitt Building. Mr. George H. Garrey will take up the geological work for the American Smelting and Refining Company, of which Mr. Spurr has had charge for the last six years.

D. W. OHERN, professor of geology at the University of Oklahoma, has been appointed director of the Oklahoma Geological Survey to succeed Chas. N. Gould, who has resigned to enter private work. The survey is at work on the oil, lead and zinc, granite, and iron resources of the state and separate reports will be issued on each of these products in the near future.

E. R. Buck ey, after three years with the Wisconsin Geological Survey, seven years as director of the Missouri Bureau of Geology and Mines, and four years professional service as a mining expert, announces that he has opened an office as a consulting mining geologist and engineer at 1364 Peoples Gas Building, 122 Michigan Avenue, Chicago, IIl.

820 Scientific Notes And News.

Mr. Myron L. Futter, for many years a geologist on the United States Geological Survey, and in charge of Artesian water investigations in the Eastern States from 1903-1907, and Mr. Frederick G. Clapp, also formerly of the Geological Survey, but more recently consulting specialist in oil and gas at Pittsburg, have organized an association known as the Bureau of Associated Geological Engineers with offices at 131 State Street, Boston, and 331 4th Avenue, Pittsburg. The Pittsburg office will take over and continue the extensive practice of Mr. Clapp in the oil and gas fields, while the Boston office, under Mr. Fuller, will handle all other branches of geological engineering including water supplies, cements, and ore deposits.

At the November conference of the mineralogical department of The Brooklyn Institute of Arts and Sciences, a lecture by the president of this department, C. Roe Gardiner, with Tiffany & Co., was delivered on " The Diamond."

Proressor H. L. Faircuixp, of the University of Rochester, has been elected president of the Geological Society of America.

Tue Rev. T. A. Benprat, of Turners Falls, Mass., has been appointed instructor in the department of geology at the University of North Carolina, his appointment taking effect on January 4, IQI2.

THE value of the total mineral output of Alaska in 1911 is estimated at $20,370,000, compared with $16,883,678 in 1910. The gold output in 1911 is estimated to have a value of $17,150,- 000; that of 1910 was $16,126,749. It is estimated that the Alaska mines produced 22,900,000 pounds of copper in 1911, valued at about $2,830,000; in 1910 their output was 4,241,689 pounds, valued at $538,695. The silver production in 1911 is estimated to have a value of $220,000, compared with $85,236 for 1910. The value of all other mineral products in rg11, including tin, marble, gypsum and coal, was about $170,000, an increase over that of 1910. By using the above estimates for the output of 1911, the total value of Alaska's mineral production since 1880, when mining first began, is found to be, in round

Scientific Notes And News. 821

numbers, $206,600,000, of which $195,950,000 is represented by the value of the gold output. The total production of copper in Alaska since 1901, when systematic mining of this metal began, is about 56,700,000 pounds valued at about $8,170,000.

Bureau of Mines. New Publications. (List 7—December,

Bulletins.—Bulletin 6: Coals Available for the Manufacture of Illuminating Gas, by A. H. White and Perry Barker, 1911, 77 pp., 4 pls. Bulletin 16: The Uses of Peat for Fuel and Other Purposes, by Charles A. Davis, 1911, 214 pp., I pl. Bulletin 19: Physical and Chemical Properties of the Petroleums of the San Joaquin Valley, California, by I. C. Allen and W. A. Jacobs, with a chapter on Analyses of Natural Gas from the Southern California Oil Fields, by G. A. Burrell, 1911, 60 pp., 2 pls.

Reprints.—Bulletin 21: The Significance of Drafts in Steamboiler Practice, by W. T. Ray and Henry Kreisinger, 62 pp.; reprint of United States Geological Survey Bulletin 367. Copies will not be sent to persons who received Bulletin 367. Bulletin 26: Notes on Explosive Mine Gases and Dusts, by R. T. Chamberlin, 67 pp.; reprint of United States Geological Survey Bulletin 383. Copies will not be sent to persons who received Bulletin 383. Bulletin 29: The Effect of Oxygen in Coal, by David White, 80 pp., 3 pls.; reprint of United States Geological Survey Bulletin 382. Copies will not be sent to persons who received Bulletin 382. Bulletin 30: Briquetting Tests at the Fuel-testing Plant, Norfolk, Va., 1907-8, by C. L. Wright, 41 pp., 9 pls.; reprint of United States Geological Survey Bulletin 385. Copies will not be sent to persons who received Bulletin 385.

The Bureau of Mines has copies of these publications for free distribution, but can not give more than one copy of the same bulletin to one person. Requests for all papers can not be granted without satisfactory reason. In asking for publications please order them by number and title. Applications should be addressed to the Director of the Bureau of Mines, Washington, mf.

822 Scientific Notes And News.

THERE has just been issued from the press a new publication by the West Virginia Geological Survey, Morgantown, W. Va., an important volume which those interested in oil and gas have been eagerly expecting for several months. This volume is described in the following extract from the printed circular of the Geological Survey.

" Detailed County Report, on Wirt, Roane and Calhoun Counties, 573 pages -+ xx, with case of 3 maps—topographic, geologic and soil—published under date of July 1, 1911, and ready for delivery in October. Besides the detailed study and description of all the rocks, minerals, soils streams, industries, etc., found within the area, the geologic map gives also the true location of all the oil and gas pools developed up to July 1, 1911, and shows by structural contours the several anticlinal and synclinal arches including the southern extension of the famous burning springs or volcano anticlinal. Price, with case of maps, postage paid by the Survey, $2.00. Extra copies of geologic or topographic map, 50 cents each. Send remittance to the West Virginia Geological Survey, Morgantown, West Virginia, Lock Box 448."

Index To Volume Vi.

[Nore.—In this index the titles of principal papers and the -headings of departments, as Discussion, are in italics.]

Abella, E., on gold in Mindanao, 134

Absence of concave surfaces, 648

Accumulation of oil and gas, 142; conditions for, 377; mode of, 12

Accumulations of oii and gas in formations having moncclinal dips, Notes on the occurrence of (Clapp), 1-12

Accuracy, in geologic surveying, 182; of fie'd assays of water, 347

Active rocks, 327

Adam, J. W. H., on classification of ore deposits, 329

Adams, F. D., on flow of rocks, 312

Adams, F. S., The iron formation of the Cuyuna Range, 60-70, 156-180

Addiasseurch, A., on copper deposits of Khirgiz Steppes, 569

Addicks, on composit.on of anode mud, 28

Adularia, 788

Africa, copper deposits of, 575

Air conditions in the Colorado mine,

Albite, 792

Albite-diorite, analysis of, 736

Albit'c rocks, 55

Allan, A., Recent literature on economic geology, 85, 197, 415

Alloys, of gold, 276

Altaite, 2!

Alumina, in Cuyuna ores, 159

American Chemical Society, the rules of, governing the proximate analysis of coa!, A plea for the revision of (Campbell), 562

American Nettie mine, tions of, 552, 553

American Oilfields well, Midway oilfield, 150

Amphibole, 240

Be gee magnetite os

Amphibole magnetites,

Colo., sec-rock

, 61-62,

development of, 17

Amphibolite, 672

Analcite, 690

Analyses of some rocks and m'nerals

from the Homestake Mine, Lead, South Dakota (Sharwood), 729-786 Anaiysis of coal, A plea for revision of the rules of the American Chemical Society governing the proximate (Campbell), 562 Analysis of coal, discrepancies in,

Anderson, R., work in investigation of oil, 386

Andesite, 13, 402

Andree, K., on a goniatite at Rammelsberg, 312

Andreoli, G., on silver-gold ratio of ores, 77:

Andrews, E. B., on geologic relations of rock oil, 365

Anode mud, analyses of, 28

Anthophyllite, 745

Anticlinal and synclinal structure, 3

Anticlinal theory of oil accumulation, 370, 372

Antimony, literature on, 197

Apatite, 20, 237, 664

Aplite, composition of, 57

Apophyllite, 690

Apophyses, 544

Appalach'an oil fields, 365

Appropriations for geological veys, 181

Arber, E. A. N.,

Argentite, 19

Arizona, copper deposits of, 573

Arnold, R., on California oil fields,

sur-review

of book by,

Arnold and Anderson, on the Coalinga d'strict, Cal., 304

Arnold, Anderson, and Johnson, on origin of petroleum, 392

Aroroy district, 118; mining in, 123

Arrested anticlines, 2

Arsenopyrite, 664, 758; analysis of, 758; replacement of, 300

Asbestos, 612, 746; analysis of, 746; literature on, 93, 200

Asia, geology and ore deposits of,

Assays, of Homestake Cambrian ores, 782; of placer gold, 779

Associations of gold, Certain naturat (Lincoln), 247

Athermal replacement, 669

Atherton, on gold sulphide, 276

Atlantic petrologic region, 261

Augen, in Rammelsberg ore, 309, 310

Augite-andesite, 120

Auriferous glass, tests on, 283

Auriferous provinces, 262

Aurogenetic epochs, 261

Babcock, J., on occurrence of barite,

Bacter'al decay, types of, 809

Baguio district, 115; geology of, 117

Bain, H. F., on genesis of lead and zinc ores, 439; on lead and zinc deposits of upper Mississippi Valley, 582, 503; on precipitation by oil rock, 504; on volatile hydrocarbons, 140

Ball and Shaler, on copper deposits in Congo, 575

Balloon Hill, near Rawhide, Nev., 789

Bancroft, H., on copper deposits, 608

Banded structure in ores, 630

Banding of ore deposits, 631

Barite, 500, 664, 754; analysis of, 801; in limestone, 622

Barite and sphalerite nodule, 311

Barite depos'ts near Five Islands, Nova Scotia, The (Warren), 797-

Barite deposits at Five.Islands, origin

of, 80;

Barlow, A. E., on origin of silver of James township, 53

Barrier beaches, rdle in oil accumulation, 808

Barriers, impervious, effect on mineralization, 552

Basic rocks, Some modes of deposieee of copper ores in (Lindgren),

Bass River deposit of barite, 799

Bastin, E. S., discussion bv. 188; on graphite in New York, 220; review by. 512

Bastin, E. S., and Hi'l, J. M., The Evergreen copper mine, Colorado,

Batea, 129

Batholites, 306

Bavaria, copper ore of, 571

Bayley, W. S., review of work by, 412; reviews by, 83

Beck, R., on copper ores of Turkestan, 570; on Rammelsberg ore deposit, 306; on the occurrence of copper, 688; review of work by, 79

Becker, G. F., on crustification, 651; on gold in the Philippines, 129; on gold in waters and aqueous rocks, 258; on primary gold in igneous rocks, 252; on the geology of the Philippine Islands, 111

Beckley coal, analysis of, 564

Bedding planes, 632

Bedson, P. P., on occurrence of barium, 599

Bement, A., on the composition of coal, 453

Bensusan and Kendall, on Brazilian go'd, 30

Bergeat, A., on Mexican copper deposits, 336

Berkey, C. P., petrographic examination by, 505

Beyschlag, F., on copper deposits of Mansfeld, 580

Bicarbonates in water, determination of, 346

"Big Lime," thickness of, 47

— Utah, stratified ore deposits

Biotite, 237

Bismuth. associated with gold, 23, 36

Black Girl vein, Colo., cross-section of, 549

Black mica, 751

Black pyritic slate, 737

Blackwelder, E., and Barrows, H. H., review of work by, 319

Bladensburg oil pool, 30

Blake, W. P., on genesis of lead and zinc ores, 437; on primary gold in igneous rocks, 254

Blakemore, G. H., on composition of anode mud, 28

Bohemia, copper ores of, 570

Bohm, C. D., on tellurium in Cable district, 29

Boiler use, waters for, 353

Bolivia, copper deposits of, 575

Bonanza mine, Alaska, plan of, 547

Bone, W. A., on decomposition of hydrocarbons, 223; on hydrocarbons, 223

Bornite and chalcocite in the copper ores of the Virgilina district of North Carolina and Virginia, The

Index To Volume Vsi. 825

Boudouard, O., on oxides of carbon,

Boulder mines, Western Australia,

Boundaries, of ore bodies, 536, 647

Boutwell, J. M., on bedding in ore deposits, 633; on vanadium in Colorado, 577

Bowen, N. L, analyses by, 54, 54 (table); on diabase and granophyre of Gowganda district, 54

Bowles, O., review of work by, 83

Bownocker, J. A., The Clinton sand as a source of oil in Ohio, 37-50

Brazil, Hematite ores of, and a comparison with hematite ores of Lake Superior (Leith and Harder), 670

Breccia, 466

Brecciated structures preserved in ore bodies, 645

Breithaupt, on orthoclase, 7&8

Bremen oil, character of, 42

Bremen oil field, 40; conditions in, 45; discovery of, 41; structural relations, 5, 9

Brock, R. W., on primary gold in igneous rocks, 253

Brokaw, A. D., on secondary enrichment of gold, 257; on the solution of gold, 320

Brun, A., on volcanic exhalations,

Building materials, literature on, 101

Bua mining company, 118

Buckey coal beds, 486, 487

Buckley and Buehler, on genesis of lead and zine deposits, 437; on precipitation from metallic solutions,

Buell, I. M., on impregnation of rock by lead and zinc, 589

Bull Mountains coal field, 486

Burgess, J. A., The halogen salts of silver and associated minerals at Tonopah, Nevada, 13-21

Burrows, A. G, analysis by, 54 (table)

Butler oil pool, 40

Buttgenbach, H., on copper deposits,

Caetani and Burt, on gold at El Oro mine, 299

Calcite, 58, 636, 664, 706

Calcite-orthoclase veins from Weehawken, N. J., 704

Calcium carhonate, 748

California, The occurrence of oil and

gas in the South Midway field, Kern County (Forstner), 138

California o'1 fields, 385

Calaverite, 279

Calkins, F. C., on the occurrence of zeolites, 693

Calvert, W. R., Land classification, its basis and methods, 473-492

Calvin and Bain, on genesis of lead and zinc ores, 438; on Maquoketa shale, 432

Campbell, M. R., A plea for revision of the rules of the American Chemical Society governing the proximate analysis of coal, 562- 567: Historical review of theories advanced by American geologists to account for the origin and accumulation of oil, 363-395; on compos'tion of coal, 454; work in investigation of oil, 375

Camsell, C., A new diamond locality in the Tulamcen district, British Columbia, 604-611

Canga, 676

Canga ores, 673; analyses of, 680

Carbon,

Carbon vapors, as source of graphite,

Carbonas, 528, 537

Carbonates in water, determination of, 346

Carbon'ferous copper deposits, 573

Card, G. W.. on primary gold in igneous rocks, 254

Careri, G., on Aroroy district, 122

Carperter, F. R., on gold with pyrrhotite, 765

Carpenter coal beds, 486, 487

Carreri, G., on gold in the Philippines, 1209

Carll, J. F., on oil and gas wells, 152; work in o'l investigation, 368

Carnotite, 578: analysis of, 57:

Carthaus, E.. on primary gold in igneous rocks, 254

Cassiterite pseudomorphs, 641

Catherinet, J., on primary gold in igneous rocks, 253

Cavities, constriction of, effect on mineralization, 552; left by decrease in volume, 662

Cavity filling process, 651

Cerargyrite, 14, 17

Certain natural associations of gold (Lincoln), 247

Chabazite, 690

Chalcocite in the copper ores of the

Virgil na district of North Carolina and Virginia, The relation of bornite and (Laney), 399

Chalcocite, 399, 405

Chalcopyrite, 664, 795

Chamberlin, R, T., on gases in rocks, 223, 226, 327

Chamberlin, T. C., on composition of o:l rock, 586; on genesis of lead and zinc ores, 435

Chamberlin and Salisbury, on metals in solution, 503

Chance, H. M., on condition of gold in ores, 282; "on extraction of gold, 249; on gold i in coals, 265

Changes of level, in Philippines, 112

Channel: of access, for mineralization, 534

Charpentier, theory of replacement of, 530

Charred wood, 463

Chatard and Whitehead, on gold ores of Republic district, 33

Chemical analyses—arsenopyrite, 758; aplitic soda granite, 54 (table) ; barite, 801; Canga ores, 680; carbonates, 749, 750; carnotite, 578; chlorite from Homestake mine, 744; coal, 450, 457, 459, 460, 564; cummingtonite, 746; cupriferous sha'e, 580; diabase, 54 (table) ; enargite, 31; famatinite, 31; garnet, 753; goldfieldite, 31; granophyre, 54 (table) ; hematites, 680; hornblende from Homestake Mine, 746; iron ores, 157; limestone replaced by silica, 647; olivine diabase, 54 (table); ore from Phill ps pyrites mine, 235; ores containing tellurium, 27; patronite, 579; peridotite, 607; phonolite rock, 731; plant tissue, 462; porphyry, Homestake Mine, 734; pyrite, 755; pyrrhotite from Homestake Mine, 757; quartz diabase, 54 (table); quartz gabbro, 54 (table); runs of ore from Homestake Mine, 760; shale from Il'inois and Iowa, 587: slate from Homestake Mine, 737; soda granite, 54 (table) ; trachyticphonolitic rocks, 731; water, 340, 742; water, of Homestake Mine, 742; wolframite, 307

Chemistry, geological, The rile of hydrolysis in (Wells), 211

Cherty iron carbonate rock, description of, 165; compos'tion of, 166

Chlorine in water, determination of,

Chlorite, 58, 743, 756, 796; analysis of, 744

Chromite, 605

Chromium, literature on, 86

Chrysotile, 612

Church, J. A., on crustification, 651

Cinnabar, 21

Cirkel, F., on origin of graphite, 222; review 'of work by, 612

Clapp, F. G., Notes on the occurrence of oil and gas accumulations in formations having monoclinal dips, I-I2; on accumulation of oil and gas, 142; on occurrence of oil, 376

Clark, A. J., on silver-gold ores, 775

Clarke, F. W., on analyses of shales, sandstones, and limestones, 584; on analyses of sandstones, 803; on occurrence of vanadium, 579; on sedimentary rocks, 266, 272

Clarke, F. W., and Steiger, G., on ammonium analcite, 690

Classification—coal 'deposits, 478; coal lands, 478; valuation of, 479; criteria of ore-replacement, 619: interstices in rocks, 140; iron ores, 156; of Minas Geraes, 673; occurrence of zeolites, 690-692; oil and gas accumulations, 2; ore deposits, 80, 329; public lands, 476; replacement deposits according to physical conditions, 669: tellurium-gold occurrences, 24; waters, for boiler use, 353; for irrigation, 355

Clay, I'terature on, 94, 200, 419

Clements, F. E., on forest fires, 463

Climatic conditions in Western Australia, 493

Clinton formation, 47; testing for oil, 38

Clinton limestone, 46

Clinton sand as a source of oil in Oh'o, The (Bownocker), 37

Clinton sand, character of, 9; at New Straitsville, Ohio, 5; depth and character of, 43; stratigraphic position, 45

Cloud, T. C., on copper ore from Wallaroo Mine, 27

Clowes, os on barium content of rocks,

Coal, A plea for revision of the rules of the American Chemical Society govern ng the proximate analysis of (Campbell), 562

Coal, analyses of, 450, 457, 450, 460,

Index To Volume Vi.

562; formation of, 455; literature on, 94, 200, 714; natural history of, 810; origin of, 810; structure of, 451 ;

Coal deposits, class'fication of, 478

Coal field of Iowa, 812

Coal fields in Philippines, tion of, 114

Coal lands, examination of, 477; illustrations of valuation of, 483, 485, 489; regulations regarding, 478

Coa'ification process, 454

Coating on gold, nature of, 29

Cobalt-silver ores of Nipissing, origin, 51

Cobequid H'lls, Nova Scotia, 798

Coleman, A. P., on primary gold in igneous rocks, 252

a A. L., on silver-gold ores,

distribu-

Collins, W. H., on quartz diabases of Nipissing district, 54

Colorado, coals of, 449; copper ores of, 572, 573; oil fields of, 389; vanadium depos''ts of, 577

Columbus limestone, 46

Comb structure, 650

Comparison of Brazilian and Lake Superior iron ores, 683

Composite analyses, 584

Composition of coal, The relation of texture to the (Grout), 449

Concave surfaces, of ore deposits,

Concentration of gold, 272, 7or1 Conditions under which replacement occurs, 667 Connect'cut, copper in, 688 Conservation, 475; some results of, 314 Consolidated Mining Company, 118

probable

Constriction of cavities, effect on mineralization, 552 metamorphic replacement,

Contact

Contact metamorphism, 471, 707 Contact phenomena, 54-55 Contemporaneous deposition of chalcocite and bornite, 409 Contemporaneous replacement, 660 Cooper. A. S., work in investigation of oil, 385 Copper, in Homestake ore, 762; in Paracale district, Philippine Islands, 131; in Wisconsin, 5043 literature on, 85, 197; origin of, 335 Copper and lead deposits in sandstone, 569

Copper with zeolites in basic lavas,

Copper mine, Colorado, The Evergreen (Bastin and Hill), 465

Copper ores, 335; origin of, 689; of Germany, 570; of Virgilina district, origin of, 410

Copper ores in basic rocks, Some modes of deposition of (Lindgren), 687

Copper ores of the Virgilina district of North Carolina and Virginia, The relation of bornite and chalcocite in the (Laney), 399

Copper sulphide veins in basic lavas, 604; in intrusive basic rocks, 696

Coquillion, F., on decomposition of methane, 223

Cornu, F., on the occurrence of copper, 687

Coro-coro copper deposits, 575

County reports, 185

i F., on occurrence of barium,

On G. H., The origin of the lead and sinc ores of the upper Mississippi Valley district, 427-448, 582- 603 ;'on copper in Wisconsin, 594

Creek waters, analyses of, 743

Criteria of replacement ore-bodies, 527, 619 i

Crosnier, L. on primary igneous rocks, 253

Cross-bedding, 635

Cross sections. See Sections

Crustification, 650; of ore, 631

Crystalline structure of dolomite,

Crystallization of order of, 15

Crystallography, elementary, 412

Crystals, faceted, in country rock, 620

Crystals, in igneous rocks, 625; in metamorphic rocks, 624; in ore as evidence of replacement, 658: in sedimentary rock, 620

Cummingtonite, 745, 747; analysis of,

gold in

silver haloids,

Cupriferous shale, analysis of, 580 Cutler, H. C., discussion by, 190 Cuyuna ore deposits, pitch of, 65 Cuyuna iron ores, 156; chemical constituents of, 158; mineralogical composition, 160; origin of, 168; secondary concentration of, 168 Cuyuna Range, The iron formation of the (Adams), 60, 156

Cyanide method, of gold extraction,

Dacy Flat ore-body, 545

Daintree, R., on primary gold in igneous rocks, 252

Daly, R. A., on changes of level, 112

Datolite, 690, 796

David, T. W. E., on occurrence of diamonds, 608

Davis, A. B., on effect of water on hydrocarbon compounds, 139

Davis, R. E., on genesis of lead and zine ores, 438

Dawson, J. A., analysis by, 54 (table)

Day, D. T., on Bremen oil, 42; on dissociation of petroleum, 139; on fractionation of oil by fuller's earth, 379

Dead rocks, 327

Deerwood iron formation, 60

De Kalb, C., on compression of gaseous hydrocarbons, 148; on primary gold in igneous rocks, 253

De Launay, see Launay, L. de

Dens'ty, of Cuyuna ores, 162

Deposition of chalcocite and bornite,

409 . . Deposition of copper ores in basic rocks, Some modes of (Lindgren),

Deposition of ores by organic matter,

Depth cf—alteration in Virgil'na district, 408; Clinton sand, 43; Cuyuna ore concentration, 69; haloids, 14; m'ning, in Western Australia, 499; te'lurium-gold veins, 26; zone of oxidation, in Aroroy district,

Derby, O. A., on iron ores of Brazil, 671; on primary gold in metamorphic rocks, 271

Desert Queen fault, 15

Determination of common rocks, 83

Devereux, W. B., on assays of gold from " fossil placers," 779; on free gold in Homestake ores, 764; on primary gold in sedimentary rocks,

Dewey, C., on cummingtonite, 747

Diabase masses containing ore deposits, 53; forms of, 54

Diagrams—composition of ferruginous cherts and ores, 171; composition

of Deerwood iron formation

, 172; fossils, alteration to ore,

Index To Volume Vi.

638; heat of reaction in carbon combinations, 225; Homestake ore constituents, 761; islands in ore bodies, 655; volume changes in development of iron ores, 177

Diamond, 513, 610

Diamond Iccality in the Tulameen district, British Columbia, A new (Camsell), 604

Diatomaceous origin of oil, 392

Diatoms, 393

on copper in sea water,

Differentiation, use of term, 52

Differentiation produc's in quartz diabase masses of the silver fields of Nipissing, Ontario (Hore), 51-

Dikes, 243, 469 Diller, J. S., review by, 612 Dilution of water for examination, Dimensions, of bodies, 533 Dip, of iron formation, of Cuyuna Range, 62, 65 Discission spaces, 648 Discussion— Additional factors in the origin and accumulation of oil (Johnson), 806 Magmatic differentiation a factor in the occurrence of ore shoots (Pope), 503 Notes on Goldfield (Cutler), 190 Special problems and their study in economic geology (Walcott), 71; (Brock), 72; (Ashlev), 72; (Emerson), 72; (Branner), 73: (Buckley), 75; (Cornell), 77; (Bast'n), 188 Teaching of economic geology to mining engineers (Stewart),

replacement ore-geology

Disseminated replacement, 55 Dissociation of petroleum, 139 Dixon, H., on oxides of carbon, 227 Doelter, C., on development of analcite, 692 Dole, R. B., Rapid examination of water geologic surveys of water resources, 340-362 Dolomite, crystalline structure of, 640; replacement of, 560 Dome accumulation of oil, 381 Dome structures, origin of, 384 Don, J. R., on extraction of gold,

Index To Volume Vi.

248; on gold in waters and aqueous rocks, 258, 259; on primary gold in igneous rocks, 253; in sedimentary rocks, 2

Drake well, Titusville, Pa., 363

Dredge, native, in Philippines, 130

Drift, 61

Driftless area of Wisconsin, 506

Drilling, in Cuyuna range, 60

Dry holes, occurrence of, 8

Du Bois, G. C., on primary gold in igneous rocks, 252

Dull coal, 456

Dumble, E. T., on copper ores, 571

Dunite, 606

Dunn, R. L., on primary gold in sedimentary rocks, 267

Dussert, M., on ore deposits of Algeria, 333

Dykes of quartz diabase, character 'of, 55

Earseman, W. A., tigation, 371

Earth's crust, gold content of, 272

East Huel Lovell carbona, 537

Eaton, F. M., analyses by, 348

Eckfeldt, on primary gold in sedimentary rocks, 268

Economic geology, Recent literature on (Loughlin and Allan). 85; (Loughlin, Allan, and Schofield), 197, 415; (Loughlin), 520; (Loughlin and Goodspeed), 710

Economic reports, 185

Eddingfield, F. D., on Baguio mineral district, 117; on gold in Nueva Ecija, 132

Editorial—

Some probable results from conservation, 314-317

Egleston, on absorption of gold by plants, 264

Electrolytic dissociation, 212

Electrum, 277

Elkhorn mine, Mont., 555

Ells, R. W., on the occurrence of copper, 688

Embolite, 14, 17

Emmons, S. F., on copper deposits of Cananea, 336; on copper ores, 571; on genesis of ore deposits, 530, 531; on Homestake ores, 772; on replacement ores, 633

Emmons, W. H., on copper ores, 571; on gold deposits in Nevada,

work in oil inves-

337; on minerals of Philipsburg quadrangle, 29; on secondary enrichment, 126, 257, 329

Enargite, 31

England, copper ores of, 570

Engler, C., on origin of petroleurs,

Ep: 'losite, 50

Epigenetic origin of ores, 527

Epigenetic ores, 568

Eschwege, on iron ore from Itabira do Campo, 671

Eureka ore-bodies, 543

Eveland, A. J., on Baguio mineral district, 117

Evergreen copper mine, Colorado, The (Bastin and Hill), 465

Evergreen copper deposit, origin of,

Evergreen mine, location and development of, 465

Evergreenite, 469

Examination, Rapid, of water in geologic surveys of water resources (Dole), 340

Extraction of gold, methods for, 248

Faberik, 129

Faceted crystals in country rock, 620

Faerver, copper in, 687

Fairbanks, H. W., on primary gold in igneous rocks, 254

Fairfield County, Ohio, oil in, 40

Famatinite, 31

Farrell, J. R., on copper deposits of Katanga, 575

Fault preserved in ore body, 642 Faulting, in Goldfield district, in Pachuca district, 504

— in replacement ore bodies,

Iqi;

Ce: 58. 238

Felsite, 730

Ferguson, H. G., The gold deposits of the Philippine Islands, 100-137

Ferrier, W. F., on primary gold in igneous rocks, 253

Ferruginous cherts of Cuyuna district, description of, 162; composition of, 164; density and porosity, 164; photographs of, 175

Field methods for water examination, 343

Field tests of water, 340

Finlayson, A. M., on pyritic deposits of Spain, 335

Fire assay, for gold extraction, 249

Fire in the Homestake Mine, 739

Fires in forests, 463

Fissures, 536

Five Islands, location of, 797

Five Islands, Nova Scot a, The barite deposits near (Warren), 797-805

Fletcher, H., on Devonian of Nova Scotia, 798

Florence oil field, 12, 389

Fluorite, 664, 753

Fluorite replacing limestone, 623

Fluorspar, literature on, 714

Foerste, A. F., on the Clinton formation, 47

Foraminifera, 393

Foraminiferal test,

Forbes, D., on primary gold in igneous rocks, 25

Forest wood superficially

Form as a criterion of replacement,

replacement of, charred,

) Forstner, W., The occurrence of oil

and gas in the South Midway field, Kern County, California,

Fossils, in replacement ore bodies, 658; replacement process in, 635; use in determining replacement,

Fractionation of oil, 379

Free gold, 26; in Homestake ore, 764

Friedrich, K., on gold in waters and aqueous rocks, 260

Fryer Hill, Colo., section of, 551

Fumaroles, action of, 327

Gale, H., S., on carnotite in Colorado, 577; on copper deposits of Idaho, 574; on copper ores, 572

Galena, 571, 664, 754; replacing limestone, 544, 624

Galena dolomite, 428, 430

Galena-oil rock theory of lead and zine genesis, 443

Galenite, 280

Garnet, 752; association with graphite, 219

Gas accumulations, classification of,

Gas (and oil) accumulations in formations having monoclinal dips, Notes on the occurrence of (Clapp), 1-12

Gas fields in Ohio, 38

Gases from fumaroles, 327

Gautier, A., on thermal waters, 326

Index To Volume Vi.

Geijer, P., on ores of the Kiruna district, 334

Geikie, A., on petrifaction, 636; on pseudomorphism, 530

Gems, of Mexico, 83; of North Carolina, 83

Genesis—copper deposits in sandstone, 576; diamonds, 611; lead and zinc ores of upper Mississippi Valley, 434; silver haloids, 13, 15- 17; vanadium deposits, 579 (see also Origin)

Geography of—Virgilina copper district, 400

Geologic history—gold, 274; Pachuca

district, Mexico, 503; Peekskill, N. Y., region, 234; Virgilina

copper district, 403

Geologic maps—Evergreen mine, Colo., 466; Philippines, 110; wolframite region of New Brunswick,

Geologic surveys of water resources, Rapid examination of water in (Dole), 340

Geologic thermometer, 228

Geological chemistry, The réle of hydrolysis in (Wells), 211

Geology of the Ph lips pyrites mine near Peekskill, New York (Loveman), 231

Geology of—Asia, mine, 466; Five Islands area, Nova Scotia, 797: Masbate Island, 119;* Mississippi Valley lead and zine district, 427, 423; Pachuca district, Mexico, 503; Peekskill, N. Y., 231: Philippine Islands, 111; Phillips pyrites mine, 231; Rammelsberg ore deposit, 304; Virgilina copper district, 400; water

supply, 413; Western Australia, 495; wolframite region of New

Brunswick, 397 Germany, copper ores of, 570 Gerrish Mountain, 797 Gilpin and Cram, on dissociation of petroleum, 139 Girard, A., on methane, 223 Glance coal, 450, 454, 456 Glass rock, 430 Glauconite, 636, 664 Gneisses, Peekskill, NG de eae Gogebic Range ore bodies, 69 Gold, assays of, 779; associated with te'lurium, 22-26; assoc'ations with vein minerals, 287-201 ; coating on, nature of, 29; concentration of,

Index To Volume Vi.

701; content in earth's crust, 272; from gypsum, 263; geologic history of, 274; fineness of, 30; in Aroroy district, 127; in heated waters, 257; in igneous rocks, 250, 284; in metamorphic rocks, 270; in organisms and in organic rocks, 264; in Paracale district, Philippine Islands, 132; in sedimentary rocks, 265; in sub-crustal waters and in veins, 256; in surface waters and in salts, 263; in veins, source of, 273; in waters and aqueous rocks, 258- 260; in Western Australia, 4097; literature on, 86, 198, 415, 520, 710; methods for extraction from rock, 248; mining of, in Philippines, 113; native, 296; tests for, 277

Gold, Certa'n natural associations of (Lincoln), 247

Gold, free, in Homestake ore, 764

Gold-altaite. crystals, 26

Gold crystals, 295

Gold deposits of the Philippine Islands, The (Ferguson), 109

Gold minerals, 275; identification table for, 281

Gold ore, sections of, 766-771

Gold ores, tellurium-bearing, Notes on (Sharwood), 22-36

Gold placers, time of formation of,

Gold ruby glass, 280

Gold selenide, 275

Goldfield geology, 190

Goldfield ore, analysis of, 32

Goldfieldite, 24, 31, 276

Goldschmidt, V. M., review of work by, 707

Goodman, M., on gold in Mindanao, 135; in Nueva Ecija, 132

Goodspeed, G, E., Recent literature on economic geology, 710

Gorham mine, coal from, 449

Goslar slates, 304

Grabau, A. W., on section in Niagara Gorge, 49

Granite-porphyry, analysis of, 735

Granites, Peekskill district, 232

Grant and Burchard, on galena dolomite, 430

Grant, U. S., on genesis of lead and zinc ores, 439; on Platteville limestone, 428

Grath'te, A theory for the origin of (Winchell), 218

Graphite, 512, 664, 755; as a geologic thermometer, 228; diversity of origin, 229; in igneous rocks, 221; literature on, 98; modes of occurrence and association with garnet,

Graphitic schists, Peekskill, N. Y.,

Graton, L. C., on copper ores of New Mexico, 574; of Shasta Co., Cal., 335; of Virgilina district, 300

Greenstone, 401

Greenstones of Sierra Nevada, 607

Gregory, J. W., review of work by,

Gregory, H. E, on Arizona, 573

Griswold and Munn, on accumulation of ol, 378

Griswold, W. T.. tion of oil, 376

Grooves, in oil sands. 7

Grout, F. F., The relation of texture to the composition of coal, 449- 464; analysis by, 459; on classification of coal, 454

Gu'lemain, C., on ore deposits of Uruguay, 333

Cuinobatan River, 119

Giirich, F., on copper ores of Bohemia, 570

Gypsum, 18, 664; literature on, 201,

copper in

work in investiga-

Haase, analysis by, 580

Hager, L., on accumulation of oil in domes, 383

Hague, A., on ore deposits of Eureka

district, 529, 661; on thermal waters, 328 Hall, A. L., on Pilgrims Rest gold

min'ng district, 338; work by, 195

Hall, R. D., analyses by, 587

Halogen salts of silver and associated minerals at Tonopah, Nevada, The (Burgess), 13-21

Haloids, 13

Hard iron ores, 156; composition of, 157, 161

Hardness in water, computation for, 350; determination of, 344

Harker, A., on dolomite, 640; on petrologic regions, 261

Harr's, G. D., on dome structure of

review of

salines, 384; on Louisiana oil fields, 11; work in investigation of oil, 383

Harrison, J. B., on primary gold in igneous rocks, 252; in metamorphic rocks, 271

Hastings, J. B., on auriferous sands, 273; on primary gold in igneous rocks, 253, 254

Hayes and Kennedy, on accumulation of oil and gas, 154, 382; on association of oil and gas, 139

Hayes and Phalen, on graphite in Georgia, 220

Heat of reaction, 225

Hematite, 671, 754

Hematite deposits, in Paracale district, Philippine Islands, 131

Hematite ore, 156, 674

Hematite ores of Brazil and a comparison with hematite ores of Lake Superior (Leith and Harder), 670

Hematites, analyses of,

Henrich, F., on thermal waters, 328

Henwood, W. J., on tellurium on Morro Velho mine, 27

Hess, F. L., on Randsburg district, Cal., 337; on vanadium deposits in Colorado, S77; review by, 318

Hessite, 275, 2!

Hewett. D. F., of Peru, 578

Hewitt, G. H., on assays of bullion from Homestake lode, 777

Hill, R. T., on oil accumulation, 381

Hillebrand and Ransome, on vana- d'um in Colorado, 577

Hillebrand, W. F., analysis by, 578; on melonite, 34; on vanadium deposits, 578

Hintze, C., on albite, 792; on magnesite with gold, 205; on native gold, 301; on the occurrence of copper, 687

Historical review of theories advanced by American geologists to account for the origin and accumulation of oil (Campbell), 363

History of geology, 708

on vanadium deposits

Hoefer, H., on the occurrence of oil, 371

Hoégbom, A. G., on Swedish iron ores, 334

Holloway, G. T., on isolating tellurium, 35

Homestake Mine, Lead, South Dakota, Analyses of some rocks and

Index To Volume Vi.

Homestake Mine, fire in, 740; gold ore of, 293; metallurgical system of, 774; water conditions in, 738

Homestake ore-body, 729

Hore, R. E., Differentiation products in quarts. diabase masses of the silver fields of Nipissing, Ontario, 51-59; analyses by, 54 (table); on orig'n of cobalt-silver ores, 51

Hornblende, 745

Hornung, F., on formation of mineral veins, 699

Hiibnerite, 20

Humphrey, H. F., analysis by, 792

Hunt, T. S., on origin of graphite, er on the occurrence of rock ol

aval. E., on the occurrence of copper, 687 Hutchison, H. S., on barite deposits,

Hyalite, 20 Hydrocarbons, as source of graphite, 222; formation of, 223; in petroleum, 138 Hydrolysis, for, 214 Hydrolysis in geological chemistry, The role of (Wells), 211 Hydrothermal replacement, 669

defined, 211; reactions

Idaho, copper ores of, 574

Idahe-Eureka-Maryland ore-shoot, 27

Idaho Springs schists, 466

Identification of gold minerals, i

Igneous rocks, analyses of, (table); at Homestake Mine, ¥ Dak., 730; Peekskill, N. Y., 232; replacement of, 560

Ilmenite, 795

Impervious barriers, effect on mineralization, 552

Impregnations, 528

Induced rock structures, 628

Intergrowth of chalcocite and bornite, 406

Interpretation of field assays of water, 350

Interruption of dip, types of, 10

Intersecting roups of fissures, 540

Intersecting joints, preservation of,

Intersection of rock structures, 647 Interstices i in rocks, 140 Intrusives, in Cuyuna iron formation, 64, 69-70

Index To Volume Vi.

Iodyrite, 14, 18

Ionization, 212

Iowa, coal resources of, 812

Iridium, in Nueva Ecija, Philippine Islands, 133

Iron, in Cuyuna ores, 158; on, 89, 198, 417, 520, 712

Iron carbonate rock, description of, 165; composition of, 166

Iron formation of the Cuyuna Range, The (Adams), 60, 156

Iron Hill ore-shoots, plan of, 541

Iron ore, titanic, in Norway, 334

Iron ore resources of the world, 332

Iron ores, classification of, 156, 673; of Minas Geraes, origin of, 681; of Sweden, 334

Tronwood formation, 60

Irrigation, ae for, 355

Irving, J. D , Replacement ore-bod 'es and the criteria for their recognition, 527-561, 619-669; The origin of the Rammelsberg ore deposit (with W. Lindgren), 303-313; on chlorite, 744; on free gold in Homestake ores, 764

Islands in ore bodies, 655

Itabirite, 671

Ivey, on selenide, 275

literature

Jacquelin, on origin of graphite, 222

Jacquet, on primary gold in metamorphic rocks, 271

Jacutinga, 673, 675

Jarosite, 18, 19

Jaspalite, 178

Jasperoid, section of, 557

Jenney, W. P., on genesis of lead and zine depos'ts, 437; on gold in coals, 265

Jennings, E. P., on copper ores, 571

Johansson, H. E., on Swedish iron ores, 334 Johnson, R. H., discussion by, 806;

work in investigation of oil, 386 Johnston, R. A. A., examination of chromite by, 605 Joint cracks, 2 Jointed structure preserved in ore, Joints,

in replacement ore bodies,

Joints, intersecting, preservation of, Junction City oil pool, 41 Juvenile minerals, 558

Kaolinite, 664, 791

Katanga copper deposits, 575

Keller, E., on composition of copper ore, 27

Kemp, J. F., on association of gold and tellurium, 22; on concentratration into ores, 272; on leaching of rocks, 273; on silver in Utah, 575; on tellurium in Montana, 25

Kenniston, C. W., on precipitation by Maquoketa shale, 5905

Kern County, Californ'a, The occurrence of oil and gas in the South Midway field (Forstner), 138

Khirgiz Steppes, copper deposits of,

Kimberlite, 514, 608

Knopf, A., on copper deposits, 607; on the occurrence of copper, 688; on zeolitization, 694

Knox County, Ohio, oil in, 39

Koeberlin, F. R,, on apatite, 237

Kristiania region, copper in, 688

Krusch, P., on classification of ore deposits, 329; on mineralizing waters, 699

Kunz, G. F., review of works by, 83

Kupferschiefer, 579

Kupferkniest, 310

Kiister and Griiters,

on hydrolysis,

Labor question in Philippines, 136

Lacroix, A., on primary gold in metamorphic rocks, 271

Lake Superior iron ores, 683

Lanang River, 119

Land classification, its methods (Calvert). 473

Lane, A. C., on diabase, 58; on quartz-diabase dykes, 55

Laney, F. B., The relation of bornite and chalcocite in the copper ores of the Virgilina district of North Carolina and Virginia, 390-411

Launay, L. de, on gold content of earth's crust, 272; on gold veins of Madagascar, 338: on ore deposits of Asia, 330

Laur, F., on primary gold in sedimentary rocks, 268

Lavas, copper content of, 604

Law of diminishing returns, 183

Lawson, A. C., on quartz-diabase dykes, 55

Leach, F. A gold, 30

Lead, literature on, 91, 419, 713

basis and

4 on purity of California

Lead, S. Dak., analyses of rocks from, 731

Lead and sinc ores of the upper Mississippi Valley district, The origin of the (Cox), 427, 582

Lead and zinc ore, production of, 590

Lead ores, in sandstone and shale, 568; of Prussia, 571

Leadville, ore-deposits of, 534; replacement ores of, 632

Lebachose, analysis of, 735

Leighton, M. O., on field assay of water, 342

Leith, C. K., i genesis of lead and zinc ores,

Leith, C. ora Ps Harder, E. C,, Hematite ores of Brazil and a comparison with hemat'te ores of Lake Superior, 670-686

Lenher, V., on tellurides, 22; on tellurium Fey see 34

Leonard, A. G., on genesis of lead and zinc Poa 438

Lesley, J. P., on condition of occurrence of oil, 369, 370; work in oil investigation, 367

Leucite-tephrite, 120

Levat, E. D., on primary gold in metamorphic rocks, 271

Lewis, V., on the occurrence of copper, 688; on zeolitization, 693

Licking County, Ohio, oil in, 42

Lignite, of Colorado, 450

Limestone, replacement of, 560; at Peekskill, N. Y., 233

Limestone outcrops, character of, 649

Limestones replaced by silica, 646

Limonite ore, 156, 675

Lincoln, F. C., Covtain natural assocations of gold, 247-302; on constituents of volcanic emanations, 226; on free gold in Homestake ores, 764; on Klondike gold, 273; on native gold, 294; on volcanic gases, 22

Lindgren, W., Copper, silver, lead, vanadium, and uranium ores in sandstone and shale, 568-581; Some modes of deposition of copper ores in basic rocks, 687-700; on anhydr'te as a gangue mineral, 338; on change in volume in ore-replacement, 664; on copper deposits, 572; on disseminated replacement, 556; on example of crustification, 654; on gold in waters and aqueous rocks, 258; on metallogenetic epochs, 261; on metasomatic processes

in fissure veins, 531; on ore deposition, 409; on orthoclase as a vein mineral, 788, 706; on primary gold in sedimentary rocks, 267; on pseudomorphs, 530; on replacement of crystals, 625; of soda by potash, 735; on Swedish ores, 334; on the occurrence of copper, 688; on vein quartz, 794; review by, 79

Lindgren, Waldemar, and Irving, J. D., The origin of the Rammelsberg ore deposit, 303-313

Lindgren, Graton, and Gordon, on copper ores, 572; on ore deposits of New Mexico, 331, 333, 335

Liparase, analysis of, 735

Liparose, analysis of, 735

Literature of ore deposits in I9I0, The (Ransome), 325

Literature on economic geology, Recent (see Recent literature, etc.)

Liversidge, A., on gold in bittern, 264; in kelp, 265; in waters and aqueous rocks, 258, 259; on primary gold in igneous rocks, 252

Lode fissures, 539

Lode gold, source of, 273

Lodes, gold, 498

Loevy, J., on silver-gold ratio of ores, 77

Loftusia, 639, pl. 13

Lorraine, copper ores of, 571

Loughlin, G. F., Recent literature on economic geology, 85, 197, 415, 520,

Louisiana oil fields, 11

Loveman, M. H., Geology of the Phillips pyrites m'ne near Peekskill, New York, 231-246

Lucas, A. F., work in investigation of oil, 380

Lundbohm, H., on Swedish iron ores,

Lungwitz, E. E., on absorption of gold by growing plants, 264; on gold in waters and aqueous rocks,

Luzon, description of, 111

Mabery, C. F., on evaporation of hydrocarbons, 142

McCleary coal beds, 486, 487

McCreath, on composition of coal,

McGee, W J, on origin of petroleum,

McKittrick formation, 144 Maclaren, J. M., on aurogenetic

Index To Volume Vi. 835

epochs, 261; on gold from Clogan mine, 301; on gold in coal, 265; on primary gold in sedimentary rocks, 267; on source of gold, 273

Magmas, differentiation in, 52

Magmatic differentiation a factor in the occurrence of ore-shoots, 503

Magnes te, 664

Magnetic belts, 61

Magnetite, 237, 664, 674, 748, 754; development in cherty iron carbonate, 177

Magnet te deposits, in Paracale district, Philippine Islands, 131

Magneti'e rock, description of 167; composition of, 168

Maldonite, 277

Manganese, agency in concentrating gold, 329; in Cuyuna ores, I literature on, 713

Manganese-bearing veins, in Aroroy district, 126

Mansfeld copper-bearing shales, 579

Maps—Aroroy district, Philippine Islands, 119; Baguio district, Philippine Islands, 116; Brazil, showing Minas Geraes iron district, 670; Cuyuna Iron Range, 62; M: dway oilfield, 149; oil rock, of upper Mississippi Valley, 507; Paracale district, Philippine Islands, 128; Philipp'nes, showing distribution of mineral districts and coal fields, 114; Rammelsberg, location of, 304 (see also Geologic maps)

Maquoketa shale, 432; section of, 586; as source of lead and zinc, 583, 602

Marcasite, 279, 583, 636

Martite, 674

Masbate Island, description of, 119; geology of, 119

Mathews, E. B., Relat'on of scientific to practical work in state surveys,

Matte, analyses of, 28

Mays we'll, Midway oilfield, 150

Medina shales, 49

Melonite, 33

Mendenha'l, W. C., review by, 413

Mercury, literature on, 92

Merrill, G. P., on primary gold in igneous rocks, 253; on vanadium in Colorado, 577

Mesabi formation, 60

Metallization, in Asia, 330

'

Metallurgical system at Homestake Mine, 774

Metamorphism, graphite produced by, 220

Metasomatism, 330, 531

Meteoric waters, rdle in mineralization, 699-700

Methane, decomposition of, 223

— 751; analysis of, 752; literature

n, 98

Mica schists, Peekskill, N. Y., 233

Microcline, 237, 241

Micropegmatite, formation of, 57-58

Microphotographs—dike rock, Evergreen Mine, Colo., 472; quartzvalencianite vein, 791; rocks, 238- 242, 766-771

Midway oil field, location, 143

Migrat on, of hydrocarbons, 141; of oil through rocks, cause of, 387

Miller, F. B., on silver-gold ratio of ores, 778

Minas CGeraes, iron ores of, 670; geology of, 671

Mindanao, gold deposits in, 134

Mine waters, analyses of, 732

Mineral charcoal, 452, 458; analyses of, 450, 460

Mineral districts in Ph'lippine Islands, distribution (map), 114

Mineral Farm ore-body, S. Dak., 554

Minera! paints, literature on, 98

Mineralizer, 217

Minerals, associated with gold, ig in limestone, 664; in ores, 664; 0 the Homestake Mine, 748

Minerals from the Homestake Mine, Lead, South Dakota, Analyses of some rocks and (Sharwood), 729-

Minerals, juvenile, 558; renascent,

Mining conditions, in Philippine Islands, 135

Mining districts, of Philipp'nes, 113

Mining in Western Australa, The progress and prospects of (Montgomery), 493

Minshall, F. W., work in oil investigation, 370

Miocene rocks, 121

Miocene shales, Midway oilfield,

Mississippi Valley lead and zinc dis: trict, 427; structural geology of,

Mizpah vein, 15

Model anialeg drill holes, 66-67 Modes of deposition of copper ores

Moffit and Maddren, on copper deposits, 605

Moissan, H., on metallic carbides,

Molybdenite, 396; literature on, 92

Monazite, literature on, 98

Monoclinal dips, 2

Monoclinal structure, 4

Monroe limestone, 46

Monterey shale, 392

Montgomery, A., The progress and prospects of mining in Western Australia, 493-502

Monzonite, 239, 470

Moricke, W., on primary gold in igneous rocks, 253, 254

Morozewics, J., on primary gold in igneous rocks, 252; in metamorphic rocks, 271

Morrey, C. B., on role of bacteria in organic decay,

Morro Velho mine, 27

Mosquito Creek series, 405

Mottramite, 570

Mount Vil-lon, 11

Mulga, 404

Multiple fissuring, 538

Munn, M. J., on movement of oil, 141; On pore space in shales, 140; work in investigation of oil, 376

Munster, C. A., on gold in waters and aqueous rocks, 250

Muskingum County, oil in, 42

Nagyagite, 280 ; Nakamura, K., on silver-gold ores,

Native copper with zeolites in basic lavas, 687

Native gold, 275, 206; figure of, 278

Natural associations of gold, Certain (Lincoln), 247

Natural Carbon Paint Company, 585

Natural gas, literature on, 90, 201, 410, 521, 714

Natural reservoirs of oil and gas, 143

Newberry, J. S., on oil reservoirs, 367; on origin of ore deposits, 520; on silver in Utah, 575

New Brunswick, Recently discovered lanai deposits in (Walker),

Newfoundland, copper in, 688 New Guinea, copper in, 688 New Jersey, copper in, 688 New Mexico, copper deposits of, 572

New River coals, analyses of, 564 New Straitsville oil pool, 41

Niagara limestone, 46

Nichols, J. C., on gold in Mindanao,

BS Pre Nickel, literature on, 713 Nicolai greenstone, 695; copper ores

of, 606

Nipissing, Ontario, Differentiation products in quartz diabase masses of the silver fields of (Hore), 51-59

Non-glaciated area of Wisconsin, 506

North Carolina and Virginia, The relation of bornite and chalcocite in the copper ores of the Virgilina district of (Laney), 390

Notches, in oil sands, 7, 10

Notes on Goldfield geology, 190

Notes on tellurium-bearing gold ores (Sharwood), 22-36

Notes on the occurrence of oil and gas accumulations in formations having monoclinal dips (Clapp),

Noyes, A. A., on ionization, 215

Nullagine conglomerates, 496

Oberstein, a. d. Nahe, copper at, 687

Occurrence of oil and gas in the South Midway field, Kern County, California, The (Forstner), 13

Occurrence of zeolites,

Ochsenius, K., on mineralizing waters, 700

Ohio, oil pools of, 4-7

Oil, accumulation of, 806; migration of, 387; from shale to sandstone,

Oil accumulations, present-day conditions of,

Oil and gas, behavior in underground reservoirs, 150; literature on, 99, 201, 419, 714

Oil and gas accumulations in formations having monoclinal dips, Notes on the occurrence of (Clapp), 1-12

Oil and gas accumulations, classification of, 2

Oil and gas in the South Midway field, Kern County, California, The occurrence of (Forstner), 138

Oil in Ohio, The Clinton sand as a source of (Bownocker), 37-50

Oil fields in Ohio, 37-38

Oil horizons in McKittrick formation, 145

Index To

Oil pools in Clinton sand, 30

Oil reservoirs, conditions for, 367

Oil rock, 431; analysis of, 586

Oklahoma, copper deposits of, 572

Olive Mountain, location of, 604

Openings in rocks, 534

Ordovician in western Ohio, 47

Ore concentration on the Cuyuna Range, sequence of, 180

Ore deposit, the Rammelsberg, The origin of (Lindgren and Irving),

Ore deposits, literature on, 102, 207, 421, 522, 719; origin of, 527; treatise on (Beck), review of, 79

Ore deposition from magmas, 52

Ore deposits in ro10, The literature of (Ransome), 325

Ore preserving rock structures, 629

Ore-bodies, Replacement, and_ the criteria for their recognition (Irving), 527, 619

Ore-shoots, 534, 535

Oregon, copper in, 688

Organic content of the Maquoketa shale, 585

Origin and accumulation of oil, Historical review of theories advanced by American Apes to account for the (Campbell), 363

Origin of—accumulations of oil, 806; barite deposits at Five Islands, 803; coal, 810; cobalt-silver ores of Nipissing, 51; copper ores, 335; copper, silver, lead, vanadium, and uranium ores in sandstone and shale, 568; Cuyuna iron lenses,

; Cuyuna iron ores, 168;

domes of Gulf coastal plain, 384; Evergreen copper deposit, 470; granophyre, 54-55; graphite deposits, 220; iron ores of Minas Geraes, 681; lead and zinc ores of upper Mississippi Valley, 582; natural gas, 139; oil in shale and sandstone, 141; ore deposits, 527; petroleum, 130, 301; pyrites ore of Phillins mine. N. Y., 244: pyritic deposits of Huelva, Spain, 335; Rammelsberg ore deposit, 312; textures of coal, 456; Virgilina copper ores, 410; zeolitic copper ores, 680; (see also Genesis)

Origin of graphite, A theory for (Winchell), 218

Origin of the lead and sinc ores of

Volume Vi. 837

the upper Mississippi Valley district (Cox), 427, 582

Origin of the Rammelsberg ore deposit, The (Lindgren and Irving),

Original rock structures, 628, 630

Oro La Plata mine, section of, 542

Orthoclase, 754, 788

Orthoclase-bearing veins from Rawhide, Nevada. and Weehawken, New Jersey (Rogers), 788-796

Orton, E., on arrested anticlines, 2; on Clinton oil sand, 45; on structural terraces, 374; work in investigation of oil, 373

Owen, D. D., on genesis of lead and zinc ores, 434

Oxides of carbon, 225

Pachuca district, Hidalgo, Mexico,

Pacific petrologic region, 261

Pack, J. W., on gold in waters and aqueous rocks, 258

Paint rock, description of, 166; composition of, 167

Palmer, C., on goldfieldite, 2t

Panning, in the Philippines, 129

Paracale district, 129; mining operations in, 130; occurrence of ores in,

Parallel groups, of fissures, 530

Patronite, 578; analysis of, 579

Peat, literature on, 200

ah gar 4 F., on maggots in petroleum,

Peekskill, om York, Geology of the Phillips pyrites mine near (Loveman), 231

Pegmatite, 220

Pegmatitic replacement, 669

Penobscot mine, Black Hills, 535; ore from, 545

Penrose, R. A. F., on formation of haloid compounds, 13

Percival, J. G., on genesis of lead and zinc ores, 435

Peridotite, 605; analyses of, 607

Permian copper deposits, 572

Permian of Russia, 569

Perry County, Ohio, oil in, 41

Peru, vanadium deposits of, 578

Petrifaction, 636

Petroleum, accumulation of, 806; composition of, 138; l'terature on, 99, 201, 521, 714 (sec also Oil)

Petroleum industry in Ohio, 37

Petrologic regions, 261

Petrology—Evergreen mine, Colo,

Petzite, 280

Phalen, W. C., review by, 516

Phenocrysts, 641; as evidence of replacement ores, 658

Philippine Islands, The gold deposits of the (Ferguson), 109

Philippine Islands, description of, 109; discovery of, 109; arrangement of, 111; mining conditions in,

Phillips and Louis, on copper ores in Eng'and, 570

Phillips pyrites mine near Peekskill, New York, Geology of the (Loveman), 231

Phonolite, 730; analyses of, 731

Phosphates, 518; literature on, 100,

Phosphorus, in Cuyuna ores, 159

Photographs—bornite and chalcocite in quartz gangue, 405; ferruginous chert of: Cuyuna district, 175

Physical conditions under which replacement occurs. 667

Pierce, on tellurium, 2c¢

Pioneer-Midway well, Midway oilfield, 150

Pitted surface of limestone outcrops,

Placer gold, assays of, 779

Placers, in Paracale district, Philippine Islands, 132

Plagioclase, 236

Plans—American Nettie mine Colo., workings of, 553; Bonanza mine, Alaska, 547; Iron Hill ore-shoots, 541; Mineral Farm ore-body, S. Dak., 554: Mohawk mine, Goldfield district, 191-193; ore bodies, at Bingham, Utah, 634; Penobscot mine, Black Hills, 535; Rammelsberg ore body, 305; Welcome mine, Black Hills, 534

Plant tissue, analyses of, 462

Platinum, 609: in Nueva Ecija, Philippine Islands, 133; literature on, 92

Plattev'lle limestone, 428

Plea for revision of the rules of the American Chemical Society governing the proximate analysis of coal (Campbe'l), 562

Pleasantville oil pool, 41

Pneumatolitic replacement, 669

Pocahortas coals, analyses of, 564

Polybasite, 13, 19

Pope, F. J., discussion by, 503

Porosity of Cuyuna ores, 162

Porpez'te, 277

Porphyry, 732

Porphyry masses, as evidence of replacement ores, 657

Port Barrera, 122 '

Portland, S. Dak., ore shoot, section of, 551

Pogepny, F., on crustification, 651; on genesis of ore deposits, 528: on mineralizing waters, 661; on replacement in ore deposition, 645; on spaces of discission, 648; on a tree-stem replaced with galena, 637

Pre-Cambrian rocks at Homestake Mine, S. Dak., 729

Precipitation, by organic matter, 504; of haloids, 15

Prehnite, 690

Preservation of rock structures, 627

Press bulletins, 185

Pressure, in Midway oilfield, 151; needed for gas accumulation, 148; of gas wells, 45

Primary gold in igneous rocks, 252-

Primary replacement, 660

Production of lead and zinc ore, 590

Progress and prospects of mining in Western Australia, The (Montgomery), 493

Prospecting, in Philippine Islands,

Proximate analysis of coal, A plea for rev'sion of the rules of the American Chemical Society governing the (Campbell), 562

Prussia, copper deposits of, 571; lead ores of, .571

Pseudomorphism, 531

Pseudomorphs, 530, 641

Public land laws, 473

Pyrargyrite, 19

Pyrite, 237, 279, 313, 626, 664, 755, 795; analysis of, 755

Pyrite cubes, 556

Pyrites, 636

lyrites mine, Phill'ps, near Peekskill, New York, Geology of the (Loveman), 231

Pyroxene, 237

Pyroxene diorite, 243

Pyroxenite, 606

Pyrrhotite, 756; analysis of, 757

Quality of waters, 341 Quartz, 58, 237, 241, 306, 625, 664, 754, 790, 793, 795

Index To Volume Vi.

Quartz diabase masses of the silver fields of Nipissing, Ontario, Differentiation products in (Hore), 51-59

Quartz diorite, 120, 241

Quartz grains, as evidence of replacement ores, 657

Quartzorthoclasite, analysis of, 735

Quartz porphyry, 402

Quartzite, 620, 621

Quartzites, Peekskill, N. Y., 233

Quinnimont coal, analysis of, 564

Radiolaria, 303

Rainfall, in western Australia, 493

Rammelsberg ore deposit, The origin of the (Lindgren and Irving), 303

Ransome, F. L., The literature of ore deposits in I9ITO, 325-339; on downward sulphide enrichment, 329; on gold deposits in Nevada, 337; on gold tellurides, 298; on Goldfield ores, 27; reviews by, 318, 319, 412, 707, 708

Ransome, Emmons, and Garrey, on Bullfrog district, Nev., 337

Rapid examination of water in geologic surveys of water resources (Dole), 340

Ratio of silver to gold in Homestake ores, 772

Ravine, in Clinton sand, 6; in Berea sand, 7

Rawhide, Nev., orthoclase from, 788

Real del Monte district, Mexico, 503

Recent literature on economic geology (Loughlin and Allan), 85; (Loughlin, Allan, and Schofield), 197, 415; (Loughlin), 520; (Loughlin and Goodspeed), 710

Recently discovered wolframite de- a8 in New Brunswick (Walker),

Receptaculites oweni, 431

Recognition of replacement bodies, 527, 619

Regulations regarding the classification and valuation of coal lands,

Reid, J. A., on gold in waters and aqueous rocks, 258

Relation of bornite and chalcocite in the copper ores of the Virgilina district of North Carolina and Virginia, The (Laney), 309

Relation of scientific to practical

ore-in

state surveys (Mathews), Relation of texture to the composition of coal (Grout), 449 Renascent minerals, 558 Replacement, mode of operation of, 555; shown by fossils, 638; by silica, 629 Replacement deposits, classification a to physical conditions, Replacement ore-bodies, forms and dimensions of, 532 Replacement ore-bodies and the criteria for their recognition (Irving), 527, 619 Replacement ore deposits of Bingham, Utah, 635 Replacement veins, 539 Replacing solutions, 667 Republic mining district, 412 Reservoirs for oil, 388 Residual nuclei, 654 Residual structures, 632 Review, Historical, of theories advanced by American geologists to account for the origin and accumulation of oil (Campbell), 363 Reviews— Appleton's scientific primers, Geology (Gregory), Umpleby,

Chrysotile-asbestos: its occurrence, exploitation, milling, and uses (Cirkel), Diller, 612

Coal resources of Iowa, White,

Elements of geology (Blackwelder and Barrows), Ransome, 319

Gems and precious stones of Mexico (Kunz), Bayley, 83

Geology and ore deposits of Republic mining district (Umple- y), Ransome, 412

geology of the Pilgrims Rest gold mining district (Hall), Umpleby, 195

History of the gems found in North Carolina (Kunz), Bayley, 83

Die Kontactmetamorphose im

Kristianiagebiet (Goldschmidt), Ransome, 707 Lehre von den Erz!agerstatten

Practical mineralogy simplified

(Rowe), Ransome, 318 Report on the tungsten ores of Canada (Walker), Hess, 318 Tables for the determination of common rocks (Bowles), Bay-ley

, 83 Die "wichtigsten Lagerstatten der " Nicht-Erze " (Stutzer), Bastin, 512; Schaller, 513, 518; Phalen, 516 Revision of the rules of the American Chemical Society governing the proximate analysis of coal, A plea for (Campbell), 562 Rhodochrosite. 664 Rhombic crystalline do'omite, 640 Rhyolite, 732, 790 Rhyolite porphyry, 730 Richardson, T., on occurrence of barium, 590 Richland County, Ohio, oil in. 40 Rickard, T. A., on free gold, 765; on gold from Kalgoorlie and Cripple Creek, 24; on gold with argentite, 299; on occurrence of gold and silver, 257 Riquel, H., on gold in the Philippines, 129 Ritter, E., on the Evergreen copper mine, 465 Rocks, determination of, 83; structural features of, Rocks affected by replacement, 559 Rocks and minerals from the Homestake Mine, Lead, South Dakota, Analvses of some (Sharwood), Roe'ker, on silver in Utah, 575 Rogers, A. F., Orthoclase-bearing veins from Rawhide, Nevada. and Weehawken, New Jersey, 788-706 Réle of hydrolysis in geological chemistry, The (Wells), 211 Roscoelite, 578 Roth, on petrifaction, 636 Rothwell, on silver in Utah, 575 Rowe, J. P., review of work by, 318 Rubble iron ore, 678 Ruby glass, 283 Ruby Range, geology of, 218

structure of

Index To Volume Vi.

Rules of the American Chemical Society governing the proximate analysis of coal, A plea for the reuv sion of the (Campbell), 562

Russian Permian, 569

Rutile, 664

Salina formation, 47

Saline oil, phenomena attending, 381

Salines, literature on, 100

Salt, accumulation of, 381; on, 203, 521

Salt domes, 381

Salts, The halogen, and associated minerals at Tonopah, Nevada (Burgess), 13-21

Salts, ion'zation of, 214

Sampling of waters, 342

Sand, The Clinton, as a source of oil in Ohio (Bownocker), 37-50

Sand iron ore, 678

Santa Fe well, Midway oil field, 150

Santa Maria district, petroleum, 393

Sao Paulo, copper in, 687

wis sel W. T., reviews by, 412, 513,

literature

Scheelite, 20, 664 ssa R, on gold-bearing rock,

Schiste, 401, 466

Schmeisser, K., on primary gold in igneous rocks, 252

Schmitz, E. J., on copper ores, 571

Schofield, Ss me Recent literature on economic geology, 197, 415

Schrader, F. C., on copper deposits of New Mexico, 573

Schuchert, C., fossils identified by,

Schwartz, T. E., on ore deposits of Slverton, 546

Scientific notes and news, 106, 208, 320, 423, 524, 616, 722, 815

Secondary chalcocite in bornite, 406

Secondary concentration, of Cuyuna ores, 168; of gold, 28

Secondary enrichment, in Aroroy district, 126; in Western Australia,

Secondary replacement, 669

Secondary rock structures, 627, 642

Sections—American Nettie mine, 552; Black Girl vein, Colo., 549; Cuyuna iron deposits, 63; Cincinnati anticline to Allegheny Mountains, 3; Galena dolomite, 430;

gold ore, 766-771; Fryer Hill, Colo.,

Index To Volume Vsi.

551; Maquoketa shale, 432; in Midway oilfield, 153; Niagara Gorge, 49; Oro La Plata mine, ore shoots of, 542; pinch'ng out of a monoclinal oil and gas sand, 11; Plattevile limestone, 429; Portland, S. Dak., ore shoot, 551; Rammelsberg ore deposit, 305, 307, 308; siliceous ore shoots, 548; Speckle Jack, 623; tree-stem replaced with galena, 637; Virgilina copper district, 402; of well at Lancaster, Ohio, 48

Sedimentary rocks, Peeksk:ll, N. Y.,

Segregation in magmas, 57

Selerium, 33

Sericite, 791

Serpentine, 614

Sewell coal, analysis of, 564

Shale, analyses of, 587; examined for gold, 265; replacement of, 560

Sha'e bands, as evidence of replacement ores, 657

Sharwood, W. J., Analyses of some recks and minerals from the Homestake Mine, Lead, South Dakota, 729-786; Notes on tellurium-bearing gold ores, 22-36; on assays of placer go'd, 779; on native gold at Kalgoorli, 299; on native gold with sylvanite, 2098

Shaw, J., on the occurrence of lead ore, 445

Sheeted zones, 539

Shrirkage cavities, 666

Siderite, 636, 664

Siedentopf and Zsigmondy, on size of gold particles, 282

Silica, 626; in Cuyuna iron ores, 159; preserv ng rock features, 629; re- p'acing limestone, 646

Siliceous ore from Black Hills, 640

Sil'ceous ore shoots, sections of, 548

Silicification, 636; of limestone, 557,

Silver, in igneous rocks, 253; l'terature on, 86, 415, 520, 710; ratio to gold, in Homestake ores, 772

Silver ard associa'ed minerals at Tonopah, Nevada, The halogen salts of (Burgess), 13-21

Silver deposits, in Utah, 575

Silver fields of Nipissing, Ontario, D fferentiation products in quarts diabase masses of the (Hore), 51-

Si'ver-gold ratio in pannings from Homestake Mine, 781

Silver haloids, genesis, 15-17; occurrence, 14

Silver ores, in sandstone and shale, 568; in desert regions, character Or. 13

Simonin, on primary gold in sedimentary rocks, 267

Simundi, A., on primary gold in igneous rocks, 253

Single fissure ore-deposits, 536

Size of gold particles, 282

Sjogren, H., on Swedish iron ores,

Slate, 737; analyses of, 737; black, pyritic, 737; analys's of, 738

Smelting, by Philippine natives, 115

Smillie, T. W., photographic work by, 400

Smith and Brush, on cummingtonite,

Smith, F. C., on occurrence of tellurides, 754

Smith, G. O., on graphite in Maine,

Smith, W. D., on geology of Philippine Islands, 112

Soft iron ores, 156; composition of, 157, 161 .

Solids in water, computation of, 352

Solutions, replacing, 667

Solution-surface, 649

Some modes of deposit'on of copper ores in basic rocks (Lindgren), 687

Sonstadt, E., on gold in waters and aqueous rocks, 259

Source of oil in Ohio, The Clinton sand as a (Bownocker), 37-50

South America, copper deposits of,

South Midway field, Kern County, California, The occurrence of oil and gas in the (Forstner), 138

Spec'al problems and their study in economic geology, 71-78, 188-190

Speck'e Tack, 623

Specularite, 748

i A. C., on copper deposits,

Spha'erite, 664

Springfield limestone, 48

Spurr and Garrey, on copper ores of Velardefia, 336; on magnesite with gold, 295

Spurr, J. E., on fossils in ore bodies, 658: on orthoclase, 788; on primary gold in metamorphic rocks, 271; on

replacement shown by fossils, 639;

on Tonopah ore deposit, 13 Stabler, H., on alkali in water, 351 Staderman, R., section supplied by,

Stappenbeck, R., on ore deposits of Argentina, 333

State surveys, Relation of scientific to practical work in (Mathews),

Steinmann, G., on copper deposits in South America, 575

Stelzmer-Bergeat, on ore deposits,

Sterling, copper at, 687

Stevenson, J. J., on accumulation of ol, 3

Stewart, C. A., discussion by, 703

Stibnite, 664

Stone and Clapp, on the occurrence of oil, 377

" ee 630; preserved in ores,

Structural features of rocks, 627

Structural materials, literature on, 203, 521, 716

Structural theory of oil and gas accumulation, 143

Structure contour lines of oil pool, example of, 4

Stutzer, O., on juvenile waters, 326; review of work by, 512

Sulphates in water, determination of,

Sulphur, 235, 516

Summary reports, 185

Superficial replacement, 669

Surveys, state, Relation of scientific . practical work in (Mathews),

Sylvanite, 270

Syngenetic origin of some, 527

Systematic reports, 185

Tables—associations of native gold with vein minerals, 287-291; coal, analyses of, 450, 454, 450, 460, 564, 566; gold in waters and aqueous rocks, 258-260; identification of gold minerals on polished surfaces, 281; minerals, specific gravity, molecular weight, and volume of, 664; Mississippi Valley lead and zine district formations, 428; primary gold in igneous rocks, 252- 254; primary gold in metamorphic rocks, 271; primary gold in sedimentary rocks, 267; replacement

Index To Volume Vsi.

ore-bodies, dimensions of, rock structures retainable placement, 628

Talc, 743

Talc and soapstone,

Tarr W. A., on copper deposits, 572

Teaching economic geology to mining engineers, 703

Technique of water examination, 347

Tellurium, associated with gold, 23; literature on, 418; testing for, 35

Tellurium ores, analyses of, 28

Tellurium-bearing gold ores, Notes on (Sharwood), 22-36

Temblor range, geology of, 143

Temperature, relation to chemical reactions, 215

Templeton, E. C., collections by, 789

Terrace structure, 2; in accumulation of oil, 374

Testing for tellurium, 35

Texas, copper deposits of, 572; saline oil fields of, 380

Texture to the composition of coal, The relation of (Grout), 449

Textures of coal, origin. of, 456

Theories advanced by American geologists to account for the origin and accumulation of oil, Historical review of (Campbell), 363

Theory for the origin of graphite as exemplified in the graphite deposit near Dillon, Montana, A (Winchell), 218

Thermal replacement, 669

Thermal waters, 328

™ rmometer, geologic, 228

..urkelsson, T., on hot springs of Iceland, 328

Tibbals, C. A., on tellurides, 34

Timber, in Western Australia, 494

— of formation of gold placers,

Tin, literature on, 200, 418, 521, 714

Titanite, 58, 237, 705

Titanium, literature on, 92

Tonopah ores, 13-17

Tornado Mogul ore shoot, S. Dak.,

in te-literature

on,

Tourmalinization of quartzite, 621 Tower and Smith, on banding of ore deposits, 631 Trachyte, 13 Trachytic-phonolitic rocks, 731 Trachytoid phonolite, 730 Transbaikal region, copper in, 688 Tremolite, 745

Index To Volume Vi.

Trias, of Germany, 570

Triassic copper ores, 570

Truscott, on occurrence of gold, 275

Tuff, 790

iar gp district, British Columbia,

new diamond locality in the

Tulameen hey B. C., description of, 604

Tungsten, literature on, 92, 200

Tungsten ores, 318

Tuolomne-Calaveras pocket belt, 26

Turner, H. W., on copper ores, 572; on replacement by minute fossils, 639; orthoclase collected by, 788

Turner, N. L., analysis by, 54 (table)

Turner, T. N., assay by, 704

Turquoise, 20

Tyrrell, J. B., discussion by, 701; on origin of silver deposits, 53

Umpleby, J. B., on gold of Republic district, 276; on selenium-bearing ores of Washington, 337; reviews by, 195, 709; review of work by,

Underground water

Union Mine, view of, plate 12

United States Geolog'cal Survey, coal analyses by, 564; work on special problems, 1

Unsupported structures, 654

Uranium ores, in sandstone and shale, 568

Utah, silver deposits of, 574; vanadium deposits of, 577

investigations,

Valencianite, 788, 790, 792, 795

Valuation of coal lands, 479

Van Hise, C. R., on formation of zeolites, 693; on genesis of lead and zinc ores, 438; on oil in sandstone, I4I

Vanadium, literature on, 714

Vanadium ores, in sandstone and shale, 568, 577

Veatch, A. C., work in investigation of oil, 38:

Vein gold, source of, 27

Vein orthoclase, 788

Veins—Aroroy district, 123: Baguio d'strict, Philippine Islands, 117; Goldfie'd district, 191 ; Pachuca district. Mexico, 507; Virgilina copper district, 404

Vinton County, oil in, 39

Virgilina district of North Carolina

and Virginia, The relation of bornite and chalcocite in the copper ores of the (Laney), 399

Virgilina copper district, geography and geology, 400

Virg lina copper ores, origin of, 410

Virginia (and North Carolina), The relation of bornite and chalcocite in the copper ores of the Virgilina district of (Laney), 300

Vogt, J. H. L, on primary gold in igneous rocks, 252; on gold content of earth's crust, 272: on the occurrence of copper, 688; on titanic iron ores in Norway, 334

Volcanic gases, 326

Volcano anticline, 370

Vo'canoes, action of, 327

Voltzia sandstone, 571

Von Schulz and Low, analysis by, 32

Wagoner, L., cyanide method of gold extraction, 249; on extraction of gold, 249; on gold in waters and aqueous rocks, 259; on primary gold in igneous rocks, 252; in metamorphic rocks, 271; in sedimentary rocks, 267

bile F. L., review of work by, Walker, T. L., Recently discovered

wolframite deposits in New Brunswick, 396-398 Warping, lateral, 10; longitudinal, to Warren, C. H., The barite deposits near Five Islands, Nova Scotia,

Washburne, C. W., on Florence oil field, 12, 389; on occurrence of oil,

Water, analyses of, 742; of Homestake mine, analyses of, 732; rdle in ore formation, 16, 325

Water. Rapid examination of, in geologic surveys of water resources (Dole), 340

Water pools, distribution of, 9

Water resources, Rapid exam'nation of water in geologic surveys of (Dole), 340

Watersands of Midway oilfield, distribution of, 144

Water-supply, geology of, 413; literature on, IOI, 204, 420, 522, 716; in Western Australia, 494

Waters, for boiler use, 353; for irrigation, 355; for domestic use, 356

Watson and Powell, on Virginia Piedmont slates, 403

Weed, W. H., on gold in waters and aqueous rocks, 2 58; on the Elkhorn mine, 5553 on the occurrence of copper,

Wacteker N. J., orthoclase from,

Welcome mine, Black Hills, plan of,

Wells, R. C., The réle of hydrolysis in geological chemistry, 211-217

Western Australia, The progress and prospects of mining in (Montgomery), 493

Western Australia, climatic conditions in, 493; physiographic features of, 404

West Virginia Geological coal analyses by, 564

White, David, on formation of coal, 454; reviews by, 810, 812

White, I. C., on the accumulation of oil, 371; work in oil investigation,

Survey,

White River region, copper in, 688

Whitford, H. N., on mangrove swamps, 122

Whitney, J. D., on genesis of lead and zinc ores, 435

Wilde, P. de, on gold in waters and aqueous rocks, 259

Williams, on gold sulphide, 276

Winchell, A., on oil reservoirs, 367

Winchell, A. N., A theory for the origin of graphite as exemplified in the graphite deposit near Dillon, Montana, 218-230

Winchell, H. V., editorial by, 314

Winslow, A., on genesis of lead and zinc ores, 437

Wire gold, 2.

Index To Volume Vi.

Wisconsin, copper deposits of, 504; non-glaciated area, 5

Withdrawal from entry of lands, 476

Wolf, T., on primary gold in igneous rocks, 252

Wolframite, 307, 664

WVolframite deposits in New Brunswick, Recently discovered (Walker), 306

Woodward, H. B., review of works by, 413, 708

Woolsey, L. H., on occurrence of oil,

Worcester and Bourns, on geographic changes in Philippines, 112

Wright and Larsen, on quartz as a geologic thermometer, 229

Wright, C. W., on replacement in rocks, 735

Wright, F. E., on the occurrence of copper, 697

Wulfenite, 20

Wirttemberg, copper ore of, 571

Yates, B. C., on the Homestake Mine fire, 740

Yellow Springs limestone, 48

Young, G. A., on primary gold in metamorphic rocks, 271

Zechstein, 580

Zeolites, 690; modes of occurrence, 691: formation of, 692

Zeolitic copper ores, origin of, 680

Zeolitization, 690

Zinc, literature on, QI, 713

Zinc blende, 583

Zinc (Lead, and) ores of the upper Miss'ssippi Valley district, The

origin of the (Cox), 427, 582 Zircon, 754 Zoisite, 240