PAGI

~E

SIDNEY MINING CO., largest pro­ IDAHO'S PINE CREEK AREA which produced some 1,650,000 tons of ore ducer, mills about. 270 ton daily. averaging about 3.5% lead and 8.0% zinc from 1942 to 1950, inclusive, de-

Pine Creek-Where Small Mines

J. C. KIEFFER, Manager Spokane-Idaho Mining Co.

Kellogg, Idaho

THE PINE CREEK AREA i;; about 8 miles long by 3 miles wide, extend­ing southeast from the town of P inehurst, in the central pa r t of I daho. The Bunker Hill smelter and the Sullivan Mining Co.'s zinc re­

90

SPOKANE-IDAHO MINING CO. (formerly the Constitution) is second largest producer in the area, milling about 180 tons of ore per day.

duction plant are located at Kellogg only a few miles away from the dis­trict.

Although Pine Creek is one of the oldest known mineral bearing areas in the Coeur d'Alene district, it has been one of the most ma­ligned. Many claims were located on Pine Creek before the turn of the century. Following original discov­eries, much money wa. spent in opening up the deposits and in

E ngineering and Mining J ournal-Vol.I52 ,No .6

building mills. Pr ior to 1940 none of these attempt resulted in success­ful operations on a continuing basis . Reason for these failures were as follows:

1. Ore deposits had more zinc than lead. For many years zinc was more detrimental in lead ore than gangue because the lead smelter as­sessed a much higher penalty against it. Even lead-free zinc ore when shipped to a zinc reduction plant, brought very little return. Because of these conditions no zinc ore was produced in the Coeur d' Alenes prior to 1905, and for many years after 1905, the only zinc ores produced were from ex­tremely rich bodies containing little lead.

2. The problem of separating the zinc and lead minerals from each other was in most cases so difficult as to be beyond solution with jigs, tables and vanners, the machines then in use.

3. Transportation facilities for the area were POOl'. This shortcom­ing was abou t t o be overcome in 1917, when railroad surveys were made from near th present town of Pinehurst to the H ighland-Sur­prise and Constitution mines. Work was begun in the f~ll of that year. The projec t was a bandoned, how­ever, in 1918 after several miles of road bed had been built. The money

o l

SCALE IN Ft:

5000 J

SHERWOOD

WALLACE MINER

serves commendation because of the small mines which struggled through HIG HLAND SURPRISE MINING CO. years of adversity, eventually to become important producers of strategic metals. mi lls about 100 tons daily.

Are Becoming Major Producers which had been advanced for the venture suffered the same fate as most other capital put into the Pine Creek area up t o that time.

Fortunately, since the early day fa ilures, much has been learned about the geology of the area, and successful milling methods for Pine Creek ores have been developed. A network of roads has been built to make operating mines and most of the prospects readi ly accessible.

How the Orebodies Occur

While the geology of individual properties is invar iably complex and still presents some unsolved prob­lems, the real picture is now quite well known. All the ore deposits are in the Prichard Formation, which is the lowest of the Belt Series of Pre-Cambrian sedimentary rocks which underlie the Coeur d'Alene mining district. The Prichard con­sists of blue shales and slates with where expused in this vicinty. Creek anticlinal axis, which follows subordinate interbedded gray sand Most of t he ore deposits li e along an irregular course between the stones and quartzites. In the Pine a zone of major fracturing which Placer Creek fa ul t and the fracture Creek area the f ormation is sepa­ extends from t he Highland-Surprise zone ; and the middle Prichard rated into upper, middle and lower mine to the Hypotheek mine. This quartzites, which intersect the frac­members by several massive beds of zone runs in a northwesterly direc­ turing. This intersection OCCllrs in quartzite that occur within the se­ tion and is about five miles long. some ins tances within th e present ries. The upper Prichard is 5,000 to The principal structural features of mine workings, and in other in­6,000 ft. thick; the middle Prichard the area, in addition to the fractur­ stances below any present ·workings. from 1,800 to 3,00 0 ft.; and the ing, a re the Placer Creek fault, Three properties, namely, the Hi­thickness of the lower Prichard is which lies to the south and roughly la rity. t he Douglas and the Spo­not known because its base is no- parallels the ore zone; the Pine kane-Idaho (Constitution ) , lie south

SUNSET MINERALS, INC., is the third largest operation in terms of current production. Approximately 100 tons of ore are being milled per day.

91Ju afl, 19SI-Engineering and Mining Journal

of the Placer Creek fault. These properties do not appear to be on the zone of major fracturing pre­viously described. However , the block south of the Placer Creek fault has been moved to the west, and the three mines may, in fact, lie along a di splaced extension of the main fracture zone.

Ore deposits along a given shear are localized within zones in which the ab ility or competency of the wall rock to maintain openings i" greater than elsewhere. To cite ex­amples, at Sunset l\{inerals (Lib­eral King) the oreshoots are local­ized in and near the intersection of a fracture zone with the hard, com­peten t middle Prichard quartzites, as is the case at the Hilari ty; at the Spokane-Idaho, the vein lies in the top of the upper Prichar d, in a zone in 'which beds of competent quartz­ites occur along with the incompe­tent slates, and the rake of the o1'e­body corresponds closely to the dip of the beds ; and at the Sidney, where no quartzites occur, the com­petency of the slates was increased markedly by folding before the ore­bearing fractures were made and the ore deposi ted.

Major Metal Is Zinc The major economic mineral in

Pine Creek ores is sphalerit e, al­though two properties, the Hypo­theek and Lookout Mounta in, have lead ore (galena and cerru site) with very li ttle zinc. At the Sidney and at Sunset Minerals the normal ratio of zinc to lead is about two to one ; at the Highland-Surpri se the nor­mal ratio is about three t o one; and at the other properties it is between these extremes. The s ilver content ranges from 0.2 oz. to 0.6 oz. per unit of lead. Some gold and copper are present, although usually little more than tr aces.

Pine Creek ores characteristical­ly have a fine-gr a in ed t ex ture. This is particularly true of the Sunset Minerals, Douglas and Spokane­Idaho ores. Compared with t hese three, mineralization at th e Nabob, Little Pittsburg, Sidn ey and High­land-Surprise is much coarser grained. However, even at the properties where the gr a in size is normally very fine, occasional zones are found where coarse min ­eralization exists. Thes e zones a re usually on the extremiti es of the orebody or in the walls of t he vein.

The common gangue minerals are quartz, pyrrhotite and pyrite. Small amounts of calcite and siderite a re usually present. Where massive pyrite exists the veins are usually

barren; but if the iron sulphide is ill the form of pyrrhot ite, lead val­lles are commonly f ound also. The presence of pyrrhot ite, which is a high temperature mineral, puts the Pine Creek ores in the hypothermal classificat ion ; most other ores in the Coeur d'Alene mining district are considered to be mesothermal, or in the middle t emperature range.

Mining Methods Vary Mining methods vary greatly over

the a rea. In general, however, most of the ore is extraeted by three mining methods: (1) Shrinkage stoping ; (2) cut and fill stoping; and (3 ) stull set stoping, in which the caps are cut to fit t he ground, and no framin g is used.

:'\'Iost drilling is now done with tungsten-carbide bits, although some properties are using one-pass steel bits, and other properties con­tinue to use threaded steel bits.

Development wast e is commonly used for filling. At the Spokane­Idaho plans are going for ward to augment this source of was te with Ran ds from the mill tailings. Other properties are also considering the use of sand fillin g.

A t the Sidney Mining Co., the area's largest producer, wall con­ditions are very good. Because of this circumstance whenever ore width" a re less than 15 ft., shrink­age stoping is usecl. If the widths exceed 15 ft., and t hey !'lOmetimes get as wide as 25 f t., cut and fill stoping is the method employed. Production from the Sidney mine keeps their mill running seven days per week at the rate of about 270 tons per day.

The next largest producer is the Spokane-Idaho Mining Co., which is the only mine in this area, and one of the few in the Coeur d' Alenes, where the vein is substantially ver­tical. This vein is also unique in that its strike is nearly nor th and south in contrast with the normal east-west st r ike of other Coeur d'Alene veins. Two mining practices are followed : cut and fiJI, and stull set timbering. If ground conditiom are bad because of str ike f aulting, or vein widths are very narrow, or cJoi>e sorting must be resorted to, cut and fill stoping is done; for all other conditions, stull set t imbering is used. The Spokane-Idaho is mill­ing about 180 tons per day an d op­erating their mill seven days per week.

The third largest producer is unset Minerals, Inc. The mining

method used is stull set t imbering. The dip of the vein is quite flat ,

ranging from about 20 deg. to 50 deg. Most of the ore runs into the level chutes by gravity, but if the · dip is below 40 deg. slushing must be resorted to. About 100 tons of ore are being milled daily.

Highland-Surprise Consolidated Mining Co. has been a large, con­siRtent producer f or a number of years. At present , production is somewhat curtailed to allow a vig­orous development program to be carried through . About 300 ft. per month of drifting and cross-cutting is being done, in addition to a con­siderable amount of diamond drill­ing. For vein widths up to 4 ft. shrinkage stoping is used, and for wider widths, up t o 9 ft., the min­ing method is cu t and fill stoping. About 110 tons of ore daily are being milled.

Mascot Mines, Inc., is a newly f ormed company which has taken over the Little P it. tsburg mine, for­merly operated by the Denver De­velopment Co. There has been no change in management. Stull set timbering is the mining method used. Currently, a development pro­gram is being accelerated. Upon the completion of t his program a siz­able increase in production is ex­pected. About 70 tons of ore daily are being milled.

The Nabob Silver -Lead Co. mine is under active development. Five favorable structu res were cut in their new 6,425-ft . crosscut, and each of these st r uctures will be ex­plored. The work now being done is on the Crystolite vein. Development on this vein has opened up milling grade ore, which is being processed in the company's 300-ton Relective flotation concentrator.

Other mines which are not in production but where development work is being done include the Ne­vada-Stewart, the Hypotheek, and Lookout Mountai n.

Shaft Sinking As in most other mining areas,

the Pine Creek m ines were forced to allow development work, espe­cially shaft sinking, to lag far be­hind production during World War II. Even now this cond ition of un­balance has not been entirely elimi­nated. As a consequence all the pro­ducing mines have a shaft sinking program in progress, have just com­pleted one, or are just starting one.

At the Sidney, where all ore now being milled comes f rom above the Red Cloud tunnel, which is the main haulageway, a 400-hp. double­drum hoist was recently installed. Shaft sinking in a th.ree com part-

Engineering and M ining Journa/-Vol.lS2 ,No.6 92

ment vertical shaft has progressed to thi, l,100-ft. level, which is 1,100

- ft. below the outcrop and 200 ft. be­low the Red Cloud Tunnel, where the hoist is located. A station and pocket are being cut on this level. As soon as thi s work is completed a crosscut fo r the vein, 125 ft. away, will be started, and at the same time shaft sinking will be re­sumed.

New Hoist for Spokane-Idaho

At the Spokane-Idaho a s inking program which extended the three­compartment ver tical shaft from the l,OOO-ft. level t o the l,600-ft. level has just been completed. This project opened up 200 ft. of new ground below the last working level, since a winze had previously served from the 1,000 level to the 1,400 level. Work on the 1,600 station and pocket is substan tially finished, and drifting on the 1,600 level has be­gun. Sinking in the main shaft will be resumed by March. The Spokane­Idaho is also driving a new rope raise and cutting a new main shaft hoist station preparatory to the in­stallation of a 400-hp. double-drum, tandem-drive hoist now being built by the Coeur d'Alene Hardware and Foundry Co. This hoist will incor­pOl'ate many new des ign features, such as electrically operated brakes and clutches, instead of the more common hyd raulic type.

Sunset Minerals, w hich has been mining the 1,100 level and the 1,200 level through an inclined winze from the 1,000 level, has holed through a pilot raise f rom the 1,200 level to the bottom of t heir 1,000-ft. two­compartment vertical shaft. This raise will be enlarged and timbered to extend the main shaft to the 1,200 level. The inclined winze is being sunk from the 1,200 level to the 1,400 level, with t he job now about half fin ished. The winze, which fol­lows the vein, is in good grade ore.

The Highland-Surprise has fin­ished sinking their two-compart­ment inclined shaft to the 1,450 level, and is drifting on that level.

Mascot Mines, whose main haul­ageway is the No.6 level, is deepen­ing t heir two-compartment 62-deg. inclined shaft from the No.8 level , which is 300 ft. on the incline below No.6, to t he No.6, to the No. 10 level. At th is wr iting the shaft crew is down to the No.9 level, and is cutting a stat ion and pocket there. When the station and pocket are finished, a drift crew will start driving the 125-ft. crosscut to the vein while the shaft crew returns to its sinking job.

Lookout Mountain Mining and Milling Co. is doing work prepara­tory to sinking their shaft, which is 225 ft. deep. The objective is a thrust fault believed to be 75 ft. be­low the present bottom of the shaft.

Ore Is Fine Grained

The fine grained texture of the Pine Creek ores makes milling a difficult problem. If the ores are ground fine enough to liberate the minerals a satisfactory separation can be made. Two properties which are mill ing fine-grained ore, the Spokane-I daho and Sunset Minerals, have experimented with regrind cir­cuits. At the Spokane-Idaho, which has the most difficult milling prob­lem of any of the producing Pine Creek operntions, this experiment has turned out successfully. The present flow sheet includes one re­grind mill f or the lead rougher con­centrate, and a second one for the zinc cleaner tails. The final lead con­centrate is 99 % minus 325 mesh and 90 % minus 325 mesh, and the zinc concentra te is somewhat coars­er. Fort unately the galena shows a remarkable r esistance to sliming at whatever gr ind. The sphalerite is much softer, and, if ground too fine, complicates thickening and filtering problems unduly. At the Sidney a slightly different approach to the regrind pl'oblem is in effect: here the "flash g rind," described in the ,Tanuary, 1950, issue of E & M J, by Frank McKinley, assistant mill su­perintendent for the Bunker Hill and Sullivan Mining and Concen­trating Co., is used.

The fl otation reagents ill all these circuits are the same as those gen­erally found in zinc-lead mills: soda ash and lime for alkalinity control; cyanide and zinc SUlphate for :dnc depression ; ethyl, amyl and isopro­pyl xanthat es, and the Aerofloats, for collection ; cresylic acid and methyl isobutyl carbinol for froth­ers; and copper sulphate, which several proper ties now buy in solu­tion, fol' zinc activation.

Present and Future

The zinc producing area on Pine Creek is the largest one in Idaho, which in turn leads the nation in zinc production. The Sidney and the Spokane-Idaho have been among the top ten zinc mines in Idaho for the past several years, and Sunset Minerals joined this group in 1950. The H ighland-Surprise and the Lit­tle Pitt sburg (Mascot Mines) haW' been consistently large zinc produc­ers over an extended period.

While the lead production from the area is much less than its zinc product ion, Pine Creek turns out considerable tonnage of lead concen­trates. The Sidney has for several years been among the top ten lead producers in Idaho. In 1950 the Spo­kane-Idaho was also in the top ten lead pr oducing mines.

In production of ore mined the estimate for Pine Creek up to 1942 is 1,000,000 tons; and from 1942 to 1950 inclusive, about 1,650,000 tons. Probable grade is in the neighbor hood of 3.5 % lead and 8.0% zinc.

Developments since 1942 and the continuing high demand for zinc make the outlook for Pine Creek ap­pear very good. Up to now no mine has closed because of the bottoming of its ore shoot. This, and the fact that all of the Lower Prichard For­mation constitutes a vast unex­plored zone which has not been ex­amined anywhere, give the present producer s many years of possible life. In addition, other properties not now in production will if prop­erly developed become sizable pro­ducers of zinc and lead, and will add to the alrf>..ady large production of the P ine Creek area.

New Ore Encountered

Both Nevada Stewart and High­land-Surpr ise mineR have recently encountered new faces of milling ore a ccording to Frank J. Luedke, president of both companies . The vein on the 700 level of the Nevada Stewar t which was opened up in April, has been followed for 70 ft. weRterly, of which the last 20 ft. has been taken fol' ore. The ore oc­curs in separate narrow seams of high-gra de galena, and is vastly different f rom the finely dissemi­nated zinc-lead ores common to the Pine Cr eek area. Full-width drift aSRUY:; ran 5% lead and 6 oz. silver pel' ton.

The 'vest drift of the Highland­Surprise mine on the 1450 ft. level has been in good high-grade lead­silver ore for more than 60 ft. The minera l structure varies from 1 to 3 ft. in width, and averages about 20 % lea d and 18 oz. silver per ton , with a small amount of zinc. Th e new ore exposure is believed to be the downward extension of the Surprise No.2 ore shoot mined on upper levels.

It has also been reported recent­Iyl that the Sunset Minerals com­pany is considering increasing its mill capacity from 3,000 to 4,000 tons per month.

1 According to r ecent r eports in th e Walla (e Min~,..

June. 1951- Engineering and Mi ning TournaI 93

Three Steps Toward Solving Mining's Manpower Problem:,:,·-.;" 1. What Defense Minerals Admin­ 3. What Mining Conlpanies Can istration Has done. Do.

Had metal miners put on Dept. of La­bor's critical occupation list. Had mining, milling, and' smelting listed as defense-essential industries. Prepared data to show need for blanket deferment for skilled miners.

2. What Defense M inerals Admin­istration Can Do.

Help i.n getting deferment for reservists. Advise on best use of U.S.E.S. and other Government aids. Argue indu"stry's case in Government.

Don't wait for Government to handle

manpower problem.

Determine accurately and honesrly why

people are leaving your mine.

Make wage and working cond itions as

attractive as possible.

Work closely with local draft boards.

St art vigorous recruiting campaign .

Develop effective training programs.

Employ women wherever possible.

Use foreign workers under Displaced

Persons Act.

You Can Do Something About Manpower

STEPH[i;N W. WOOD Manpower Branch

Defense Minerals Administration Washington, D. C.

THE DEFENSE MINERALS Adminis­tration-your claimant in Washing­ton on def ense matters-is eager to help the producers of defense-essen­tial materials with their manpower problems. In certain cases it can give real assistance. However, you cannot afford to depend enth'ely on Government action. To achieve rea ­sonable safety, the mine oper ator must make a very determined effort himself.

What DMA Has Done: Upon pres ­entation of t he facts by DMA, the Department of Labor has included the classification of "Metal Miner,

Underground" on th e lis t of crit ­ical occupations. Also, the Depart­ment of Commerce has listed "Met­al and Non-Metallic Mining a nd Milling" and "Smelting, Refining and Processing of Met a l" on its list of defense-essential ind ustries. Both the~e list~ are f or use by Se­lective Service a nd are in the hands of local draft boards. How­ever, mine operators and employ­ees should understan d that defer­ment is not mandatory. The list s are to assist local draft boa rds in making their decisions. T hey are merely policy guides, not instruc­tions. The deci sive power r emmns in the hand s of the loca l boards. It is up to the min e operator to present the facts an d arg ue the meri t s in each individual case for which deferment is s ought.

DMA is assembling data which it is believed may demonstrate the advisability of setting up blanket deferments for skilled workers in mines, mills, and smelters. At the present t ime, however, ther e is no t definite assurance, but simply pos­s ibility, that blanket deferments will be created. It would be foolish to relax on other ways of solving the manpower problem just be­cause of this possibility.

What DMA Can Do : DMA can give you help in obtaining defer­ments of reservists in especially

meritorious cases. However, defer ­ment should only be sought for per­sons in "critical occupations" or key jobs designated as essential. There should be ample pr oof that the loss of the personnel in question would seriously interfere wi th defense production. The military services are fully aware of the close rela­tionship between defense produ c­tion and military requirement~ . Appeals made by employees to se­cure delayeci military indu ction s hould be made a s quickly as pos­sible an d purs ued t o the highest available point of appeal. This shou Id be considered as a coopera ­tive procedure throug h which the metal producing in dustry and agencies of Government may work toward the greatest a ccomplish­ment in the nationa l interest. It s hould not be cons idered as a means of eva ding mil itary service. Bear in mind that, if delayed acti ­vation is agreed to by the military servi ces, it is in r ecognition of the greater contribut ion toward the national defense that the individ­ual may make by remaining in his civilian j ob.

DMA, insofar as justified by the facts, can work and is working to­wa rd securing bla nket deferment for defense in r egar d to reservists and Sel ective Service. However, DMA's ability to help t he industry in thi s respect depends g reatly on

Engineering and Mining Journal-Vol.152.No.6 94