Information Circular 6170: Methods of Mining Disseminated Lead Ore at a Mine in the Southeast Missouri District
Information Circular 6170: Methods of Mining Disseminated Lead Ore at a Mine in the Southeast Missouri District by United States Department of Commerce…
Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.
Received Oct 10 1929 0. 8. U. Library
Department Of Commerce
UNITED STATES BUREAU OF MINES Scotr TurRNER, DIRECTOR —
Information Circular
METHODS OF MINING DISSEMINATED LEAD ORE AT A MINE IN THE SOUTHEAST MISSOURI DISTRICT
By
Cc. F. JACKSON
circular No. 6170, september, 1929,
Information Circular -
DEPARTMENT OF COMMERCE BURZAU OF uINGS
METHODS OF MINING DISSEMINATED LEAD ORZ AT A MINE IN THE SCUTEEAST MISSOURI DISTRICT*
By Ce 2, Jackson 7
TUTRODUCTION This vaver describing the mining voractices at a mine in the Sovtneast Missouri district is one of a series being prepared by the Bureau of
Mines on mining racticos, methods, ard costs in the various mining districts of the United States.
The conditions, onereting rathods, and orac pases are those obtaining at a porresty in the Southeastern Missouri lead belt, St. Frencois County, Mo. Tunis property is the cldcst in the county and is a consolidation of a number of senarate mines originally onaued un as individual operations many vears ago. Present-darr omerntions tove uccesscrily to ba adapted to suit the olcaer levels, stoves, and pillars, and alvo ti.c recovery of ore from worked over areas which was considered too low grade to mine in the earlier' days Cons ves) a different problem than that of development and mining in virgin around.
tice described in the follovirg
Quite naturally, since this is the oldest property 4n
tne methods and details of practice nov yell standardized for the district have been
voriied out here, althousn conditions are not as favorable for their efficient application and for as good results as are the conditions at some of tne never mines,
There better opportunity is afforded to plan vork to tale advantcgeof then. In this
paper an attempt is made to outline the conditions at this oe ae and the operating methods and vr actice employed.
the district, many of
oe lOWLEDG.EUTS ,
The author. acknowledges the many courtesies extended by the manager ond
oDernating officials and their assistance and suggestions in eavnerane end compiling the material for this paver.
1 - The Burau oF Mines vill welcome reprinting, of tris paner, provided the follow-
ing footnote pee is used: "Reprinted from J. S. Bureau of Mines, formation Circular 6170. , ie
ev Mining engin ecr, U.S. a ee
In=
6354,
Inf. Cir. No. 6170.
The historical items have been taken from Geology of the Disesminatea Leas Deposits of St. Francois and Washington Counties, VYelume 9, starts 1 and 2, Missouri Burenv of Geology and Mines, by H. A. Buehler and KE. R. Backer: and the same saute: of information has bsen-drawn uvon in preparing the piragrad.s on geology and ore deposits.
History .
The first mining in St. Fra neois County, Mo., dates dack to the period fron 1742 to 1762. Winslow estimated that 1,000 tons of lead ore (500 tons of lesd) were produced in the county during the 18th century. This ore was costs ined froz shallow surface workings above ground vater level, the galena occurring as masse: and crystal aggregates in caves and crevices.
Disseminated ore was discovered et Bonne Terre in 1854, and in 136° the 3%. Joseph Lead Co. introduced tho first diamond drill into the district for exnlorinz at depth. This is probably one of the earliest if not the earliest use of the diamond drill in prospecting for ore.
. The production of St. Francois County up to 1869 vas estimated by Finslov at 124,930 short tons of ore, valued at $5,082,700. From 1859 to 1907 inclusive 1,202,607 short tons of lead concentrates vere produced, valued at $59,869,354.
At present the mines of the Southerstern Missouri lend district ara nroducing approximately 500, O00 tons of crude ore per month.
The mining method employed is ticat of open eeeues with pillar support, ani practically no timber is used. Methods and practices now in use have been developed to suit the conditions and are the result of the experience of about 50 years.
Geology And Ore Deposits
'The disseminated lead ores of southeastern Missouri occur at various hori: in the Bonneterre dolomitic limestone of Cambrian age. This formation has e¢ normal thickness of about 365 feet and, at the property discussed in this vaver, outcrors at the surface in places and comes close to surface over most of the area. Tre tes lie in an approximately horizon tal position considering the area as a whole, thors. local divs of a few degrees un to a maximum of 20° have been observed and the wnole formation has a slight dip.
The Bonneterre formation rests conformably upon tne Lamotte sandstone vith-
out any sharp line of demarcation, the lower vart of the Borneterre consisting of a transition zone composed of alternating, thin-bedded and sometimes cross-bedéed
A SS 3 - Winslow, Arthur Vol. VI cial ai of the earlier reports of tne missouri Bureau of Mines and Geolog ;
6354. eee
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ae Sess oe Figure 1.— General cross section adapted from, Missouri Bureau of Geology and Mines,
Vol. IX, part 2
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Inf. Cir. No. 6170.
ayers of limestone sla sandstone interbedded with thin lnayors of "chloritic" or
slauconitic materials: The Lamctte sandstcre Locall=, carries disseminated load near
se top and sometimes extends to consid Jerable deaths belov the Bonneterre contact.
Yo ore is being produced from th: -Lamotte, hovever, Figure l is a genera alized S3ec-
tion in the vicinity of'the mine which is the subject of this paper. The top of th
Lamotte is very uneven, causing abrupt changes in the levcl of tke ee ace ne formation is wey porous and is: saturated with water.
sOsnstee iis -daeeaees s shole, it mey' be said that the ore is segré- gated principally in the lower: 100 feet of the Bonneterre
erre, althovgen it occurs at various horizons from the tov to the bottom. The galena apoveers to favor the darter,
coarse-textured limestone beds' and the mare. shaly parts of the formation. The shale layers, which are usually thin, are often highly impregnated vith galena while the lime beds on either side are only lightly sprinkled with the mineral (Fa ig. 2 2.) AS
a rule the richest rock is so*t and somewhat decomposed, though there able exceptions to this. :
t
The ee part of the Ponreterre is often somevnat argillaceous. Overlying this formation is the Davis shell, v7 mich has a normal tnickness of 150 to 190 feet. Between the 'ton of the Ronneterre 224 the bottom econmnlex of limestone, shale, sandstcne, and glauconite, the formation is thicker bedded, 'the bedding planes being commonly 1 to 6 feat avert. Verticnl jointing in this horizon is often strong, bit the joint planes are usually 3 to 5 fect or more annet. Joint planes are sometimes filled with galena anc calcite. ;
90 called "water .chains sis" cut. across ae beds in various directions but strike predominantly in a general easterly and westerly direction. These channels 'some times start fron surface or in the overlying shale anc. pass into the limestone, and may gradually play out at cloth.. Others pass from the Bonneterze into the underlying sandstone. The larger vater channels seldom carry ore in commercial quantities, although shects of galena,and aggregates of crystals are often found in™
them embedded in reddish or brownish mud ene decomoosed dolomite, the usual filling of these ees a ed
eaten of roughly euesitel fracture zones occur in the upper horizons, individual fractures being thin, leached,. and whitened by the action of surface
waters, These are often mine. peace and frequently have "or kable ore associated vith them, .
In general, it may be said of. te. district that galena occurs disseminated through dolomitic limestone and shaly beds, in horizontal sheets along bedding Planes, in vues anc cavities, filling or lining the walls of joints and crevices, and as aggregates of cubes in channels.and.joints.
6354, Ben
Inf. Cir. No. 6170.
The greater part of the production from this particular property is nov coing from the middle and upper horizons of the Bonneterre formation, although the ore occurs over a vertical range'extending from within a few feet of the surface to a deoth of 450 feet. Mining operations are being carried on at various noriz-ns from +376 to +685, sea level datum, and ore has been mined to elevation+ 771.
The thickness of the individual ore horizons ranges from 7 feet (the mini mining height) to over 200 feet. At present, however, there are no active storey over about 35 to 40 feet high. Ina given area the ore may occur at several overlapping horizons or may be confined to only one or two. (Fig. 3 and fig. 4.)
Character Of Ore And Wall Rocks
In the middle horizons the galena usually occurs in rich horizontal lavess a few inches to a fev feet in thickness, while the intervening beds are sprinkled lightly with the mineral. Thus the ore body is composed of layers of rich ore separated by lean ore rather than of bands of ore separated by barren rock, In an ore area all the rock contains some galena. The ore of the middle horizon is nardé and breaks in'larger blocks than that in the lover and over horizons duz2 to the heavy bedding and jointing, the beds and joints being closer together in the latte. The ore in the southern part of the district oceurs largély in the lover vart of ix formation and on the whole breaks finer.
In the upper levels of this mine are numerous systems of slips and crevices, usually leached white, from which layers of workable ore make off along the beddix and fracture planes. Some of these lavers are cuite rich.
The outlines of the ore bodies are very irregular both in plan and secticz, as shown in Figure 2 and Figure 3. 'Stoping 'vidths range from a few feet along sox of the upper narrow fractures to several hundred fect. Some cof the ore bodies are 700 to 800 feet wide by over 1200 feet in length.
There is considerable variation in the strength of the formation in differ ent Iocalities, but on the whole it is very strong and will support itself over wide spans. Some scans are over 100 feet between pillars or margin walls. In other places it is necessary to limit spans to 17 or 18 feet. Shaly layers tend to slack upon exposure, and vertical channels, slips, and joints constitute other sources of wealmess in both ore and roofs of stopes. "Water channels" constitute a condition that required care in mining, both because they weaken arches and ss" and because they are sometimes active watercourses. In some parts of the district care is taken to leave barrier pillars against these channels to prevent a heavy influx of water from them.
6354. -~4
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Inf. Cir. No. 6170.
Te wall rocks are in general of the samc ciarccter as the ore; and the ore
10rizons pass laterally, sometimes sradyally and so..etimes abruptly, into barron sock.
Prospecting And Exploration
Exploration is conducted almost entirely by diamond. drilling from the surface, diamond drilling underground, and test drilling with light hemnsr drills, rarely by means of prospect drifts.
Diamona Drilling. The company ctmns and operates its own dia snond-cril] ing equipment using on surface "B!" size rods, core barrels, and bits making cores and "EX" rods witn "A" bits and core barrels underground naling l- 1/8-inch ¢ cores.
All cores are carefully examined by an inspector who, through many vears of exnerlence in the district, can estimate very accurately. the lead content of the rock. kotes are made regarding the vhysicel charactor of the core, its color, vorosity,
tae estimated lead enntent, etc., and are carefully recorded. The cores are marked and filed for future reference. These cores are not as sayed. 'The. sludge from the drill holes is dried and assnyed, and the assay Sete are recorded vita the other
The diamond drill:is used on the surface chiefly for prosnecting areas out- Side ths boundaries of tho old stoves and underground to test floors of old stopes for ore which may have been left in carly vears and for tests holes too long to drill with the ja acknammer, which is limited hers . QGovths of 2p foet. One diamcend drill is kert in operation on both @ayv and night 1ifts all the time and is moved from one section of the mine to another as Set, "the MAGEE SE an drill will average 40 . to 50 feet of hole per shift.
T6s t— Hole Trilling. Light jackhamer- ~ty2e grille ATS . employed for testing backs of old stoves, floors, and marginal areas: where the denth of hole required does not exceed 22 feet. In active stops 3s they are pike ee from the bottom of headings to test tne back before stovine uo ths bluff or bench. For testing old basics in high stopes they are operated from scaffolds suspended from the roof. These scaffolds are a unique feature of tne practice in the district, and as they arc emoloyed for other urposes they ere described later under the zenzral caption "Minins". For drilling other than dorn holes the drills are mounted on a column and are equipped vith a pneumatic feed, which is another unique feature of the practice at this property; this is described leter under "Dvrilling:and EBiasting". When operated from a scaffold for testing the roof they are sometimes mounted on a bur secured to the hanging rods, end the drill is counterveighted by passing a rove tied to the drill over a nullev in the roof ard attacking cone or to old car wheels to the other end of the rope. It is customary to test bec's vith holes drilled at the corners of 25-foot squares over the area to be explored.
6354, Peston
Inf. Cir. No. 6179,
The drills usually ere operated dry and the cuttings are cmeght in a. ae
which fits eround the front end of tie drill. The steel is mady up in 2-fo: cna starting with a six-pointed rose bit, "hich has a gauge of 1-3/4 lncnes a eae
diminishes 1/16 inch with cach chance cf steel up to the 10-foot loneth:. after wric chisel bits arc a@nployed vith gouges calivered te suit the hole. The cuttings frv each ¢ feot constitute a sumple, which is boxed end tassod; the samples ars turnci in to ti office upon going off shift. Those sarplcs ere assayed for lead and tz: values recorded.
A large vart of the vresent output of this mine is orcduced in arcas "Aic. nad been wor'ed over in early years and at that time presumed to be mined out. S:: sequent exploration, as described above, has resulted in the develooment of such o:
over tne backs, in the floors, and outside tiie margins of the old stones.
In deterinining the minaoility of an area explored by these methods the ™y- Sical characteristics of the core, such as color and textures, are ee eee eon Junction with vast exnsrience as to values at the same vertical horizon of the formation in adjacent areas, as well as the lead content indicated by the @rill sanvies. Thus a single hole showing tood valves at a given elevation, althousch sure rounded by holes showing low values or only traces of lea. at this elevation, is usually justification for the development of an area provided adjacent arcas at th: same horizon have been productive.
Estimation Of Tonnages And Valcis
In estimating ore proved as s result of Grill exploration a minimum xminir; thickness of 7 fect and 15 feet-ver cent lead are tiekeon as a basis for tne calculations. Trat is to say, ground wnich will not average 15 feet-ner cent over a 7-foot thickness is excluded from the ores reserves. Under this rule 1 foot of 15 per cent leac would be included, and as a matter of fact vwoula mine ont dotter
han the minimum grade, since the 1 foot of high grade has a much nigher core gravity than the other 6 feet of barren ground which mist be included under th
rule requiring a minimum stove height of 7 fe:t. Furthermor:, experience kas ie strated that all the rock within the boundaries of an ore body contains sone leac.
Yaere more than 7 feet are involved a calculation is first made to Geter mine whether the entire thickness is minadle, tnat is, of an averaze grade oF 2 per cent lead. If it is not, the minable thickness ne grade thereof ere deter-
mined by a cut-and-try method.
oe Inf. Cir. No. 6170. DeVoILOr 'hte
rt .
This snoueeey extends over a large area and embraces "several. of 'tho oldes + lines in the district which were originally dJeveloved as 'separate one ations.
There ave el. shafts on the vroverty that,were sun: to develop a number of separate ove bodies, whicn were in some cases widely ssvaratzd by bergen ground, [ne several productive areas have since been connected underground. by crosscuts, som2 of which are long, and now all the ore :ained is hoistcd through a single shaft, designated as No. 1 shaft. Ore is hoistsd from tro levels located, respectively, L75 feot-and 245 feet below the collar. It is located at tho mill site.
. Miis shaft is 6 by 15 feet in the piece ond is divided into three compart-_ fonts. 70 cormartnonts sre used for noisting in 2 3/4-ton slips in balance, and the other-is used as a pinevay and for noter.carlos. There is no leddcmmy in this shoft, B Fe tee oe
e :
Close to No. 1 shaft and near the change house and office is Noe 1 man shart, a shallow snaft provided with a stcirvar from the collar to the bottona. From the © bottom of this-shift access to the upper main haulage level is gained by staimzars leading dav. through.olu.stoves.
', ip Paes ; a
No. 3 shaft is eouinped with a vinigle cate snd coustortsight end is used
for handling men, explosives, and suz:lic.. -If 4s connected to both of the main naulage levels. 2 0-3 : .
Another shaft equinned with a cage snd hoist is used as a ready moans of access to a largo pum station located in an isolated and inactive section of the mine. Tucre is-no retuler.untiendnnt at tiis station, the pumps being automatically started and stopped. Yet. anotucr. soft is ywsed for lovcring heavy equipment end materiel which can not be convenicntiy, uenéled in No. 3.snail, The bottom vart of - this shaft is umtimbered and is). in fact, just 2 hich open stop. Other snafts merely assist in providing excellent-natvral ve;tilation, while still otacrs are abandoned and closed. oe
- Precticelly no timber is required to sinrort: thé sround in any of these snaafts, except right at the surfece, and. the, timbering used. is only that required lor support of guides, lives, etc.
Pesos Es ne pas
. AS stated: mien of the cresont produc tion, is 'from operations 1 areas prefiousl+ wor-ced, where suovsequent exploration has disclosed ore bodies over, beneath, and outside the oldstones. Ore is norm Yeing minzsc fron elevation +3576 to + 636 on some 10 different levels. There are tw main heulage levels 70 feet apart vortically, the umver one being at elevation +625 and the lower at+9555 sca level datum
6554. -7~
Inf. Cir. No. 6170.
at the hoisting shaft. About 75 per cent of the present output is either eee down to these levels through chutes. or is hoisted on slopes. To connect vith upper ore bodies it is' often necessary to drive crosscuts in waste to get "aie oe and then raise thereto.
In some cases access to these stopes is from upper. levels or old stoves, azi in others it is necessary to divide the raise into two compartments, one for ore the other for entrance to the stope and for air and water lines. Sometimes were x ore body is small and the cost of development per ton of ore to be recovered vow: be excessive it is more economical to tram the ore to an qld stone connecting wits a haulage level' and reload the ore with a mechanical shovel after ennvee tonnage 1 been dumped to warrant moving in a shovel.
ATI waste from devel opment is trammed and. dumped into old stones, no lasts rock being hoisted to surface. It 'is obvious that under the conditions at this minc, where most of the development is in old areas, no standard method of devalopment can be employed; rather the problem. is to fit the development in each partic. lar case to the existing workings.
Development openings and haulage drifts are untimbered. Main haulage dries are a minimum of 8 by 12 feet in cross section with the track usually in the center, a ditch on one side, and room to walk on the other. ; -
Development drifts and crosscuts are usually rae or 8 feet high by 9 to 10 feet wide. Raises are about 6 by 9 feet and are commonly driven at an inclinatica of 45 degrees, seldom vertically. 7 3
Slopes are driven to develop ore horizons below the naulsge levels, end the inclination varies up to a maximum of about 30 degrees from the horizontal. In cm section they are about 6 to 7 feat by 10 to 12. feet. From some of these slopes se* eral levels are turned off to develop as many different ore horizons.
Drilling And Blas Ting
All drilling is done with light jackhammer drills operated dry, except in confined places where the dust is not readily dissipated. As there is practically no silica in the rock the dust is not considered injurious. Furthermore, the dril:s are commonly mounted on a pneumatic feed described later, so that the miner stands back from the drill while it is in operation. The Grills are all operated as oneman machines, except in scaffold construction work. Air pressure at the drills is maintained at 75 to 80 pounds. : :
6354.0 002. 2s 8
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The 'rocl: drills easilv, and 80 to 100 fest of hole oor shift is a fair average for a machine. The steel holes its gauge well, and it is usual in development work to drill 12 holes with one: set: of, steel; even then much of the steel could te run again. In stoping pe SSeS run until the gauges will not Pon Owe: 7 a. -
In drilling drifts,.. Peaseen oc aSE leadints, and 'or osvect holes in roof or rib the drill is mounted on a.pneumatic feed vlunger operating in a cylinder or
barrel which ts held in a saddle clamp attacked to a 3 inch, single-screw column (fies. 5).
'The fies barrel can-ba-rotated through 360 degrees in a vertical plane, and by. turning ' saddle clam about the vertical 'column bar the machine can be pointed 'in any cape direction. 'he air connection for the pneumatic feed can either be made-at the front end of the piston or plunger close to tne drill machine or at the back end.of the barrel, according to the preference of tne operator. Tne former is the more common practice. Ry shutting off the air to the feed and opening the drill throttle slightly the machine backs the crill.out of me hole, 3y rotating tne plunger in the barrel, thus singing the machine out of line with the hole, the steel is easily removed and tic next steel inserted in the hole.' The length of feed is usually 30 inches, though some have been constructed with 33-inch feed.
7 Figure 6 shows the construction of the barrel, piston, and cone and Figure 7 the clamp which fits around the drill snell ani secures it tc the piston or barrel. Taese are made in the conmany shops. Tue sacéle clam) in. which the cone fits is the
standard saddle claim made by the drill manufacturers for NOE eee the drill on an . arm in the Meu manner e
' In this. uniform cutting eround, which 1s comparatively free from slips such as often siven trouble in drilling and where there is little tendency for the holes to cave, this pneumatic feed gives exceptionally good results. The air pressure behind the feed gives a'steady pressure against the rock wiich would be difficult to duplicate with the ordinary screw feed. After starting the drill the miner can stand back out of the dust or sludge and can occupy himself with cloning off the
bench to prepare for drilling stove holes or with other work while the eee is cutting.
In drilling test holes in the roof the same equipment is used. Here it is customary to attach a light clamp to the top of the column to which a pulley is secured. A rove tied to the drill and passed through the vullev, with one or two © old car wheels tied to the other end of the rove, serves to take the weignt of the machine. off the pneumatic feed. When drilling these holes from a scaffold the pneu-
matic feed is often mounted uvon a snort cross bar fastened between a pair of the hanging rods of the scaffold..
For drilling stone holes and otner holes cporoximately vertically downward, the drills are held in the hands in the usual manner.
6354, 20%
Inf; Cirs No. 6170. .
For drilling "lifters" in the stopes or other flat holes along the floor it is customary to use a "drilling board" unon which the drill rests. This consists of two par allel: strips of wood with slats nailed across the underside to forma ladder. + These strive are about 2 inches "ide, with spaces of Z inches between ths=. The "board" is laid flat on the floor in the direction of the hole to be drilled, the drill is rested upon it. The space between the side boards is such that the Grill slides smoothly upon them. After starting the hole tne driller exerts a forward pressure against the back end of the machine by means of a pinch bar insert:i between the slats and with a slat as a fulcrum. He is thus able to stand erect ™:. feeding the drill forward.
Tie machines employ 7/8-inch, hollow, collar-shanked steel made wo in 2-fo:t changes up to 22 feet in length. The six-point rose bit is used with a l 3 /4-inch starter and gauge changes of 1/16 inch for each change of steel. The steel is tiesed in a coal-fired forge and is machine sharpened in a shop on surface at No. 3 snaft. The drillers handle their ovn stesl from shaft to working face.
Each driller is provided with a tool box in which he keeps his tocl4, af spare fittings, gaskets, etc., and a detonator box.
Electric detonators in delays 1 to 6 are omployed for all development vor: For shoving and block-holing fuse and cans are used. Where electric detonators ar used the miner is supplied with a box containing a powder punch, a bundle of target rough twine, a roll of connecting wire, and a galvanometer. Where fuse is used Similar box contains a powder punch, a bundle of tarred rough twine, a cap crime, a fuse cutter, a can of watcrvroofing compound, and a reel mounted inside the box at one end, on wnich a roll of fuse is wound. The loose end of the fuse is drawn. through a hole on the reel end of the box. Over this hole and on the outside of box a bracket is fastened which is a vart of the fuse cutter and holds tne eaetne element. The latter is keovt in the box when noe in use.
Hach miner prepares his own fuse: atid 3 primers, locally termed "nifters", loads and fires his own holes. A special powder punch is used as illustrated in + sketch, Figure 8. This consists of a brass tube closed at one end into wnicha stis of powder fits easily but snugly and dovn the center of which is the punch proper Toe cartridge is pushed back to the end of the tube and is then withdrawn with a hole punched exactly in the center and half the length of the cartridge. Tie cazt end of the fuse is inserted in this hole sné pushed to the bottom. A niece of tine is then looped about the fuse close to the end of the cartridge and a hitch aroun the center of the cartridge holds the detonator in place, so that it will not pull
out. Tne aoe 1s placed in the hole with the fuse end pointing out so thrt the
6354. @ Sat ae
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Pa
Sq Pt Sep
Figure 9.— 20-hole center-cut round in 810 drift
ie ane Zo! LA Z -.. PAA ee
Figure 11.— 20-hole center-cut round in 6'X9' raise. Numbers show order of firing
Inf. Cir. Ne. 6170.
'use is not bent. The rule is to place the "nifter" next to the last stick in the 10ole, although this practice is varied and it is sometimes placed near the bottom. Tre explosive is a 40 ver cent ammonia. gelatin running about 100 sticks to se SO-pound box, Stemming is prepared in cartridges by the miner from drill cuttings and two or three stemming cartridges are placed on top of each char e.
'Wnere electric blasting is employed current is usually taken from the 22nh~
volt mine circuit. In rare instances, blasting machines. are used in remote sections of the mine where rower is not accessible.
Tvo switches ure employed, an ordinary knife switch which is mounted within Sizht of the face to be blasted but far enough-back to escape injury from the blast and a firing switch mounted some distance away.in.a locked box. The firing switch
closes against a strong spring, which keeps it open except when held in the closed position. ,
Before connecting the leai wires the miner is required to insert an electric squib across the ends to test tiem for stray currents. If the squib does not fire ne closes the knife switch and throws in the firing switch. The burning of
the squib indicates that the circuit is ell right un to that point. The trip back to the firing switch assures him that it is di.connected ana in working order. Going back to the face, he throws oit the :mife switch, removes the burned squib,
which he retains, and thsn connects the iead wires to tae connecting wires. 'The
knife switch is thrown in and then last~ the firing switch. The burned sahib is attached to a card provided for tne purpose, umon which the driller marks the date,
Dlace, and his signature and turns it in to the office at the end of the shift as
evidence that he has complied with the rzguletions of the company as outlined above.
In driving drifts, crosscuts, raises and loves, the round usually employed is a "V" or center-cut round. Figure 9:shows a round employed in an 8 by 10 foot drift and Figure 11 a round in a 6 by 9 foot raise driven at an inclination of 45 degrees. The round is varied sonewhat to suit the ground and according to the judgment of the mine>. Most of the drillers are men of long experience and unusual © intelligence and can usually sive very good-reasons for the particular variation of the round which thev are using in any special instance. :
The drift round shown was in somewhat easier breaking ground than the aver-
age, pulling 6 to 7 feet, and was broken with about 125 sticks of 40 ver cent sec~ lal gelatin. The cut holes are loaded with about 8 sticks each and the relief and Square-ups with 4 to 6 sticks each. A verhavs more common round employs 8 cut holes, the bottom lifters of the illustration being drilled as cult holes and with additiona:
Inf. Cir. No. £170.
relief holes as required. There ars usually 22 holes in the average-round, eni 24 to 26 bolts are not uncommon. ae a
@
The 20-hole raise round shovn in Figure 11 is similar to the drift rouni Six to eight sticks of owder are used in euch (of the cut holes and, an averays ci: sticks in the other holes.
; Where there is pronounced horizont:1 bedding, ospecially if there are clis nating layers of lime and shale, a modified pyramid cut (locally termed a "disse: cut) has beon found to sive better results than the "V" cut. This cut is shown in Figure 10, the position and number of relief ane Square-up holes defending won si: of drift and ground conditions. :
Thc average advance in drifts and raises is apace 28 fect ver six-Cav 7% The miners wor't in pairs with tvo, column-m7aimed, vpneumrtic-feed, jactshammer-ime drills on one shift, the round being mucked out on the opposite shift. VDeveloomes headings are driven on contract at a given vrice per foot cf advance.
Stoping
Oven stones with pillar sunvort are exmloyed for extraction of the cre, tH pillars being of the casual or irregular tyne as contrasted. with those emploved i: regular room (or stove) and pillar work. . Where the ore is not mere than 9 or 10 feet thick it is breasted out the full height. In thicker ore a heading 7 to 8 feet high is treated out immediate! under the toz of the ore and in acgvence of the stone which follows it up closcl". Toe method of breasting out thin ore is practically the same as that of dvivim headings in higher ore, as illustrated in Figure le, which olso shows the method of drilling the stove or "bluff" bre.
In the heading three holes are drilled one above the other, but the aid-te or breast hole is drilled with about 6 incnes less burden thuA the back hole an lifter. The burden is usually 3 to 4 fect, although tunis varices somewnat with fee nature of tne ground. These holes are drilled 8 to 10 Teet in depth, and occasi¢"- deeper. In the heading, tne breast hole, usually loaded with about 10 sticks o- -power, is time to go first, followed in turn by the bec''x hole and Lifter, wets. are loaded somewhat lighter. 'The face of the heading is not carried in a s:reis!
line but as shown in th2 n1hbe tention in order to provide free faces to break to
a, ree
6354. ees,
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syee1q 010}}0q Ae uodn : Surpuedap '(g) zenqds pus (z) & OYT 10 (T) ejoy edoys sz9q71e os) Y
UBid - a BXYG,, JO 2],
Inf. Cir. No. 6170.
The usual span between pillars in zood ground is 30 feet, but in Vveaver und it may be only.16 to 17 feets Where: there are old workings above or below pébars are carefully located by survey to Naatch" with the older pillars; thus soaking is often very irregular. The plan,. Figure 3, is dram to scale and WS Wren pillar spacing and arrangement.
In oie a pillar the holes are never drilled toward the pillar but tantially, as shown at X-x, to avons Ege SHavreeens or it.
After a stope is opened there are deualig tr . headings in operation, someies three and occasionally only one. One driller vorls in, each heading and the pe or bluff behind it. a ade ea
Stove holes are drilled 3 to 4 feet back of the face of the "bluff" and' spaced 6 to 8-feet apart, depending upon.the nature of the ground. Those drilled m the floor of the heading are 6 feet deep, while those drilled from the nee iches are drilled un to 10 feet in dent. ..
In a heading or low stove a drillér will usually break about 30 tons per shif
J more in higher stones. 'In "bluff" mining 90. to 120 tons ver shift 43 common. out~t2 holes or 80 to 100 fest . of drilling is an average shifts work.
The eeiVicte tiene ca contract eu. are naid for the tons of ore broken, as assured by the nuubder of cars of 25 tons capac age. he price varies with the ight of stove and nature of the ground. In low stopes and hard ground the vrice y be as high as 16 to 18 cents ver ton, for stoves intermediate height 12 to cents, and in very hich stones as low as 8 cents.
In the low stoves and healints the sround seunil is breaks fairly small, but 1 the hich stoves or bluffs consideratls secondary breaking is often required. wilders requiring block-holing can usually be pushed to one side by the mechanical 1ovel to be. ae and blasted at the end of the shift.
Loum . In develovument work sna. in stones where enough ore can not be 'broken to cep a mechanical loader busy the ore is shoveled into cars by hand. The usual ask or. "score" for a hand loader, is 20 tons. Tis score is reduced, hovever, where. oading ig difficult, as when there is a long tram. Tne mucker does his own trammnng from the siding or "loop", as it.is locally called, to and from the loading
oint, ordinarily using a mule.
OA. ms ore
Inf. Cir. No. 6170.
At present there are seven mechanical loaders in the mine. These are of t: shovel or "dinner" tyoe, mounted on caterpillar traction, and have a full 360-dez: swing; the diaper discharges its ,load directlY into mine cars. These shovels are ( two different types. One is @quipped with a single 25-hp., A. C. motor, all three motions being operated through clutches to the same drive. The other has separate drives for esch motion. This shovel is described in detail by Van Barneveld.
The shovels are operated by one man, who usually also transfers his om cx fron the locomotive gathering loop to the shovel, using a mule. The shovel ovnerat: is paid for loading under a bonus system whereby a "score" or task is set for "hic: he receives a regular daily wage, and additional payment is made for tonnage ix é- cess of this. The usual score is 42 cars of 23 tons capacity each, but this is vr to suit special conditions. Occasionally in extreme cases it is as low as J2 cars,
or as nigh as 48 cars.
Tvo muckers are usually employed in each develcoment heading and are 8, 10, or 12 hours pay for mucking out the round. This amounts to a bonus f ing a clean set-up for the drillers working on the opposite shift.
Stope Suppcrt
The st~es are supported on irregular circular pillars, and no timber is for this purpose. Pillars are commonly spaced with an intervening span of 30 fee, sometimes as little as 17 or 18 feet, and in sone of the older workings the spacingé is 40 - 50 and even &0 feet or more. (Figure 3.) It is estimated that 10 ver cen of the stone areas is left in pillars.
In high stones the old pillars are often very irrsguler in shave and size from ton to bottom, due to differential weathering of the lime and shaly layers or to slabbing along slip and joint planes. The shaly. lavers tend to slack and cri ble, often leaving pillars shaped like an hourglass or several superimposed nouglasses. Vertical jointing iy tiie rock also serves to weaken pillars, and wnere a prominent joint is close to a pillar face a largo slab may scale off.
These conditions have made it necessary in many instances to reinforce pillars when their continued maintenance is required. In some instances unite has been applied to ston slacking ection. In others it has been necessary to en large the villars by building forms around them and filling with concrete, and is still others villars are wraoved with old cable over vertical rods, lie the hoops OEE ee eae ea seo 4 - Van Berneveld, Charles E., Mechanical Underground Loading in Mztel Mincs; 3. Ss
Bureau of ijines, and University of Missouri School of Mines and Metallurgy. 1924. vo. 142-152.
6354. ~]4—
Inf. Cir. Yo. 6170. na barrel, Another vtactice is to drill horizontal holes throug the pillar fbrough which heavy tie rods are employed to hola tie pillar tog cether. Sone of the stoves are verv old, and in one section of the mine villars over 00 feet in height are standing. The active stones are low in comparison, very fev eing over 35 to 40 feat hich; but inasmuch as they ars often above or below old topes and tie villars are matched" with older pillars, they constitute in effect, ong continuous pillars with the floors acting as beams betweon them.
Scaffolding
A unique feature of the practice in the Southeastern Missouri lead belt is ne use of scaffolding suspended by hanging ruoés from the roof of the stove for nsoection and trimming of roof and pillars, for crillirg test holes for explora- 'ion purposes, or for gaining access quickly and cheavliy to ore otncrwise accessi-— le with difficulty in order to onen it uo for development and mining.
In high ground the active life of envy stopes has been very long, and alshough the ground is verv firm and strong the roof may become weakened along bedding planes, enaly layers, slips, and channels ive to lone exposure to the air. The scaffold affords a quick, chean and safe method of access to the roof for insvection and fcr tri st ee down loose enOnnes '
In strong rock similar to this the tendency wnen failure does occur is for the ground to cone in big blocs. The use of scaffolds as constructed and employed to-day is tne outgrowth cf an incident some 12 or 13 vecrs ago. A large slab of loose ground avreared on the side of and at the tov of a villar about 100 feet high in an active stope. In the roof above it another loos3 slab opened uo so tnat work in tne stove had to ston. 'The pillar stood about 49 feat from the rib of the stone, along which was a traveling road. A S-incen plank 13 feet long was run out fron the traveling road and jacked against the back with two ¢rill columns. A minor tnen went out part wey on the plank and drilled holes in the roof, in which eye bolts were inserted. From these hanging rods were dropped to support the plank. Holes were drilled further ahe:d and the scaffold extended till the loose ground was within reach, when it was safely barred down. The present practice has become ocretty well standardized, and tiie men have become ex.ert and rapid in this work. The men work in pairs and secure themselves by ropes fastened around the body and fastened at the other end to a solid anchorage. 'Tivo men will often extend a scaffold 00 to 70 feet in a shift; in fact, 100 feet has been done.
In starting a scaffold access is gnined to the ton of the stone by means of ladders or a roadway along the side of the stope. An anchorage is made in tne rib or floor of the roadway, and two holes are drilled ahead in the roof of the stove ebout 3s feet apart, the line between them being et right angles to the intended
6354, wh Be
Inf. Cir. No. 6170.
direction of the scaffold. These holes look. ahead at an angle of about 45 degrees and are drilled. to a cevth cf 14 inches. (Figure 13.) Eyebolts of l-inch round
wrought iron with ends split to receive a wedge xre inserted in the holes and drive
up tightly. Hcnging rods of l-inch round iron 7 feet 5 inches in length are then
hooked into ths e:rebolts, and a cross var, also of 1- inch round iron, is howzed into the eyes at the bottom ends of the ueernee
Tivo 2-inch planks 8 feet in lengtn are secured to the crossbar by U tolts of 3-inch iron which pass through holes bored about 6 inches from the ends of the planks. Tne vian-s are then pushed ahead to the position shown, the hangers then being at an angle of about 45 degrees from the vertical. The planks are anchored at the rear end, as shovn in the sketch, or may be secured to horizontal anchor rc 3 by means of U bolts. ss eae
One Griller then stands on the outer end of the scaffold and guides the drill in starting the next pair of holes, while the other operates the drill froz the floor of the scaffold further back. The operation is revealed, the rear ens of each pair o7 blanks veing secured by U bolts which are long enough to pass tar pe tvo planks, one on tov of the other, as shovm. The roof. is ot course tested and loose ground barred down as the scaffold advances.
Some of these scaffolds are several hundred feet long. Changes in directic: can be made as desired, and often they ars jumped from cne elevation to another either uv or down to suit changes in the elevation of the roof.
The scaffolds are often guyed or braced tc 'stone walls, roof, or pillars to 'prevent side sway.
Transportation
Main haulagewavs are laid with 56-nound rails to 24-inch gauge on closely spaced well-tamped wooden ties. The roadbeds are well ballasted, granulated slag being used for this nuryose in some sections. The curves *%re casy, the rails are
brace with standard steel reil braces, and the ster reil is properly elevated. Long switch points are emoloyed ane are connected to low, cross ~throw switch stands.
On neulageways over thich more than ove locomotive peavels semi eutonatic block signals are installed, which are operated by the locomotive engineer from nis seat while the train is in motion. At some other mines of the cone ful): e300 matic block-signal svstems Zave-*been installed. All switches are protected wits automatic lights which snew red for the turnout or for a split switch. Tae lights arc in pairs, so if one burns out the other will shov. This equipment is carefully inspected and maintained in perfect working order all times.
uoMonzsu0d ployeos pepuedsng — 'cy em3iq
suo ployeos jo sire} Hod xoqoue ,T
er
aoull punoz me i reqesor1y
ON scence
% Inf e Cir e oO e Sl 70) ®
Te trolley wire is carried on one si@e about 12 inches outside the rail and is suspended from substantial iron hanger ~ods inserted in holes drilled in the roof. Where tne roadway passes through hich stoves, -as it frequently does, galvanized-iron
wire cross suspension is employed.' Rails are bonded with standard flexible rail bonds arc-welded to the rails. - an
The main-line haulage locomotives are the manufacturer's standard 13-ton design modified to conform with the mining comoany!s specifications 'and actually weignt about 15 tons. They are driven by tvo 90 hn. motors and geared to a speed of 15 miles per hour. They pull a maximum of tuirty 2a ton cars; 16-car common, and on one haul where the grade is 2-3/4 ver cent against the loads for 4,800 feet 14 cars to the train are customary. This ae srade is-in a long. crosscut connecting with a section of tne vroverty formerly operated 'as a separate mine. The average main line haul is 0. 79 mile as 'figure on the ton-mile basis.
trains ore
Trivitary locomotive haulag ays are "Laid with 40—nound rails and mule haulage and hand tramminzg roads a. yr eOLesune or 2£O-pound rails. Sidingsor loops, as they are termed locally, are established at points nepr the working faces and at tons and 'Dabvons of inclines for storsags of empty and loaded cars. Electric signal systems betveen these looks ond tic shart are emloycd to notify tre locomotive engineer wuen a loaded train is ready at anv particular loop. Mules are usually em- Mloved to transfer cars between the loops and loadin: niLeacz2s. Fav mls driver
ere emdlozved such, the loader usunll doin' Lis ovn treming. - Some hand traming
is done on over levels for 'tromin 1g oo dis bEace gs to ¢hutes and in sore instances in development 'ork. ao
on
Tne standard car is of 25 tons onpacity and eas a solid, rectangular body without doors." The car 0ay is of 3/e-i uch iron, reinforced by corner angle irons snd a heavy bend around the too built woon four S-inch."8" beams. The box is 6 feet 4 inches long by 4 fect wide by 1 foot 9 inclies deep; and the ton is 3 feet 4 inches above the rail, which is a convenient height for looking with the mechanic2l shovels and not too hizgn for hend landings. Ts running geor is of standard railroad tyne, l6-inch wheels dressed on a 2- i5/1é-inen- axle between railroad-tvye journal coxes having half brasses and secured to the "7" beams of the cer body. Swivel couplings
for dumping tn rotary dumps-vithout uncoupling avo connected to ioevy sirius arawv-
vars; flat single links vith round pins for cooling cars are used.
td
Tac exrs are ruled to the start in trains of 14 to 30 cars on ench of the tvo main levels and orc dunoed % cors at tine without uncouplins by motor-operated rotary dumps. Heavy flat-stcel plates under the outside "H" beans of the car and
vrojectinz slightly beyond the sides thereof are caught under ansla irons running
the full length of the rotary 'thas holding he' cars in position on tne r-ils
during dumping. Tne vocitet into vnicn the ears are. dumped extends from belov the
6354. 7
Inf. Cir. No. 6170.
lower level station to the upper level and has a total capacity of 1000 tons of or: Tae flov of ore from the vocxet into the steel manganese-lined chute is controlle by arc gates, operated by hvdraulic cylinders. . "At the lover end of tne chute a7 tical undercut gate, also operated hydraulically, controls the loading of 2-3 /4-te capacity skips. The space between the upper arc gates and lower undercut gate is not a measuring chute in the true sense of the vord,- inasmuch as it: holds vractically 2 skips of rock, but it provides a szefety feature in loading. The lov-r undercut gate is not actuated when the upper are gates are up and in this Way Or vents a runaway of. ore from the pocket aoe me shaft.
Hand traming on the upper fevers ia done with cars of l-ton capacity. fT: are square-body cars without doors and are dumped in a cradle.(Pig. 14.) In this cradle the car is turned end over end. Some of. the ore from chutes is wet and ten: to pack and build up in the corners and bottoms of the haulage cars. In suth irstances sheets of heavy oiled pvaner are employed to cover the bottoms of the cus before they are loaded and have been found to eliminate the trouble. There are ot a few chutes in the mine; these are 3 feet in width and are equipped with heavy 2 gates operated by long lever arms.
Power enters the mine at 440 volts a.c. and motor-generator sets are emlced to transform to 275 volts d.c. for haulage. On long haulagevavs, 300,000 c.n. feeder lines are carried in varallel with the trolley to hold up the voltage; 4(- volt lines are carried to the stopes, where banks of transformers are omployed to step down to 220 volts for mechanical shovel operation. set of semiportable tra formers is supplied with each shovel; these are moved from place to place as the shovel moves and are set on the ground a short distance back of the shovel.
At No. 3 shaft, which is used for handling men and suvvlies, safety gates are installed at each level. These are arranged to cut off the current to the caz hoist automatically when in the open position, so that it is impossible to :sove tt 'hoist when a gate is open at any level of the shaft.
mat
Wage, Contract, And Bonus Systim
Drilling and blasting and loading are generally paid for under a bonus Sy5- tem, which is based upon an old, pre-war scale that covered various classes of wor and conditions and was of course much lower than the present basic scale of wages.
In this district the labor turnover is very small, and many of the mine*s have worked in these mines for a long term of years. Long familiarity with the old prices which had been established for various characters of work and conditions enables the men to figure their own earnings without explanations from super visory officials, which is a most desirable feature in any contract or bonus system.
Inf. Cir. Mo. 6170.
All nen are guaranteed the basic daily wiee ($5.05 per shift). Contracts re figure! at the ole unit vortices, and tne amount in excess of the old daily vare imes tne number of shifts worl. is added to the present basic wage rate times the amber of shifts worked to calculate the total ancunt vaid in each case. Eight hours constitutes a shift.
Drilling. Drillers ave vaid a set vrice ver foot of advance in develovinent ork and in stoves and stove headlines for the nut of tons broken, as measured y the number of 2,- -ton cars loaded, recorded by car cnec'ters enmloyed for tnat purose. Drillers furnish only their labor and powder, whicn is sold to them bv the omopany at a fixed orice somewhat lower than the actual cost price, wnile. the company furnishes drilling equipment, tools, md compressed air.
Prices for drifting, veising, and sin'ting vary with the character of the Tound, Size of excavation, and accessibility of the working nlace. The machine xen carry their ovn steel to aud from the shaft, no "nipners" being emmlored.
In stoves the unit vrice varies principally with the height of the stone hough character of ground, access:oility of the stowe, etc., may be given considertion also. This price is 16 to 13 cents ner ton in low ore and 12 to 14 cents in omewhat higher ore, to a minimum of 8 cents ver ton in hitn stopes or "bluff min-
Loacins. Prices for loading ore in stoves, wietuor by hand or mechanical order, vary with the heignt of Stove, tramming distance, ead character of the wort. land loadevs tran their own cars ans) rcinarily use 'a mule for transferring cars beween the loop and tne mck vile. Ordinarily the mechanical shovel operators tram neir own cars in tie same manner, unless there is enough muck to warrant mule rivers being emvloved.
The usual basic or Hscore, ae it is termed for a hand maker, is 20 tons, or loading which he receive only tre regular daily wage. In excess of this he ecelves a bonus for each oe ton loaded. In places wnere there is a lonz tram, ad tramming, or badly scattered muck, the score may be reduced to as little as 14 r lo tors,
In devclooment -rork if is customary to pay & to 10 or 12 hours for mucking ut the round, defending unon the size cf the excavation and loading conditions. mere the -micir is all in one nile, 2s at tne foot of a raise, and other conditions fe normal only 8 hours are usually vaid, while in driving a slone where loading is o& 86 easy as in tae e ift, and where tn2 mickers heve to go up and dovn the slope O° operate the hoist 12 hours would be the averore pay.
ry
O4, Bae
Inf. Cir. No. 6170. SAFETY WORX
The safety organization of the company, "hich operates a number of mines and plants, is under the direction of cne man, tho is responsible only to the 2Zeneral manager. He has a number of assistants, ench of whom is assigned the ins c- tion of a definite part of the company's operations.
A continuous campaign in safety education is directed toward developing "safety-mindedness" among the men by means of talks and posters. At the varticula mine covered b;y this report there is a screen at the foot of both entrances to tic mine upon which is flashed at the beginning of each shift a safety picture or meii' so that it is seen by all the men upon going to work. The picture is changed ever day or so, and the apparatus is connected to a time clock so taonat the lignt cones on automatically at the risht hour and remains on for half an hour.
The general superintendent, superintendent, mine captain, foremen, and tos: together with the safety engineer assigned to e:ch mine, act es the safety comnitt of that mine. Suggestions from the men as to safety measures are encouraged, but thers is no worknen's safety committee as such. Tne safety score of each forensn and boss is kept carefully, and each boss is responsible for ths safety of his men. One of these has a record of avvroxinately 32,000 shifts without a lost—time accident.
The company gives no first-aid training, but first-aid instruction is give: periodically by the U. S. Bureau of Mines to sé@lected men, when the Bureau of iMin-: car is in the district. Due to the fact that the company hospital is close at han and the attendance of a physician can always be hed in a very few moments, firstaid treatment is not encouraged. There are, however a number of trained first-aid men' in various sections of the mine to act in cases of extraordinary emergency.
6354. £96.
Cost Data for ay, Avorago_iignth 1929,
Tons ore loaded - mining 49,700 (25,500 loaded mechanically Tons ore loaded - ievelonment 4,300 (24,200 hand loaded Total tons ore loaded eeseers 04,000 Tons rock loaded Pee ale onah wad 2,000 Develop-, Mining Total® ment : A. lLabor-man hours per fon. : Breaing (drilling and blasting) : 511 1625 ~208 B/ Muckine (hand) aa.d4 waste eouw ate aeeee eek 587 0416 : 3/ Macking (mechanical) ceecceeceece 061 S/ Mucking (total) <..0s.esvaseaeaenatessave 2231 4/ Transportation (havlage and hoisting) ... 184 IS STOR Gaye) 6 ae Aa mn ee a ~034 2031 PrOSUCCCINS sg wea se Ae aee be eae ee ee ; : eO15 General, includes drainage, machinists, etc. 0126 SUSY 1S 2 On: in vise swe opts dae cata eee ew aan 032 OG) -saiaslat te sess cis went oh ware usec tg ener Wiebe oe . 527 Tons vcr man shift, all underground latr a 9.67 Labor, per cent: total Us Gs Cost: nica csacdes ' 50% 75% 72%
B. Power and supplies. Pover, Kv.h. ver ton ) AY COmmresst on: ws ewee wes ee eee Sel NOIStINe Sot ah ieeaewea Side eseaig ail a lecasbasl aries oes! 0.5 PORTIS gt axe as eet ecs aera eee wes ee ee eee 5.0 MecOansCAl LOR Oine: esas ieee Serre eee ee Q.2 Te Si 2 2 6 ene. Meera ta wesc oh acta desea toate wees See QO.7 Die Gin wes nea etaes ee ee re ee eels QO.2 Totel power, ku.h. oer ton 10.3 Exnlosives, 40 per cent ammonia gelatin, HOURS: PCL "COM woss.s ace ene De eee eee eee 1.524 459 "00 Povrer and sunvlics, ver cent of total under-' SPOUNENCOSG sated ls iS oakine towed cane oe ) 50 25 i 28 Ce Percent of total 0st: <aiitisaaaeeeaecuseoues 18.7 81.3 100
1. Based on tons of ore and rock loaded from development.
2. Based on total tons ore loaded.
3. Includes mule haulage by loadexs between looks and face.
4, Includes overstion, maintenance of track and cars, roadmen, stablemen, sand drying, etc.
6354, -21~
Figure 14.— Cradle dump for 1-ton car from "Fifty Kinks in Metal Mining", 1920, Engineering and Mining Journal
Figure 5.— Mounting for pneumatic feed
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Figure 8.— Powder punch