I. C. 6555

DEPARTMENT OF COM M ERCE

UNITED STATES BUREAU OF MINES

SCOTT TURNER, DIRECTOR

INFORMATION CIRCULAR

MILLING METHODS AT THE CONCENTRATOR

OF THE WALKER MINING CO.,

WALKERMINE, CALIFORNIA

BY

M. R. McKENZIE AND H. K. LANCASTER

, I

MARCH, 1932 (

I.C.6555. March, 1932.

INFORMATION CIRCULAR

DEPARTMENT OF COMMERCE - BUREAU OF ~INES ;==========================================================================================

MILLING METHODS AT THE CONCENTRATOR OF THE WALKER i,IINING CO., WALKERMINE, CALIF. 1

By H. R. McKenzie 2 and H. K. Lancaster 3

INTRODUCTION

This paper describing the milling methods at the Walkermine concentrator, Plumas County, Calif., is one of a series being prepared by the United States Bureau of Mines on milling methods and costs in the various mining districts throughout the United States.

ACKNOWLEDGMENT

The authors wish to acknowledge their indebtedness to James O. Elton, manager of the International Smelting Co., and to Henry A. Geisendorfer, manager of the Walker Mining Co., for permission to present this paper; to H. A. Geisendorfer and J. D. Ro be rts, shift boss, for historical facts, and to D. D. ~acLellan, geologist, for geological information.

LOCATION

The Walker mine and mi ll are located at Walkermine, Plumas County, in the northeastern part of Californi a and at an elevation of 6,200 feet in the Sierra Nevada . Walkermine i s about 27 miles northeast of Portola, a division point on the Western Pacific Railroad which is about 60 miles west of Reno, Nev.

Weakher conditions and heavy snowfall usually make the road between Portola and Walker­mine i mpassab le -during the winter and early" spring months. During this period, transporta­tion of passenge r s and supplies is conducted over an aerial tramway 9 miles long the terminal 0"1' which terminal is located at Spring Garden, Ca11f.- Construction of this tramway, which was built chie fly for the sh ipment of concentrates, was completed in October, 1920 .

GEOLOGY

The geolC GY of ·the Walker mine depos it is described in detail by J. S. Diller in U. S. Geological Survey Bulletin 353, 1908, Geology of the ' Taylorsville Region, Calif.

In brief, the oreboqies occur along a shear zone which cuts through a highly garneti­ferous schist, known local ly as the Robinson schist. The ore shoots, which are composed of chalcopyri te in quartz and silicified schist, are not connected and ma.y be regarded as individual deposits. Toey range from 300 to 2,000 feet in length and from 5 to 100 feet in width .

1 -' The Bureau of Mines will welcome reprinting of this pape~. provided the following footnote acknowledgment is used:

"Reprinted from U. S. Bureau of ;.rines Information Circular 6555."

2 One of the consulting en gineers, U. S. Bureau of Mines, and mill superintendent, Walkermine concentrator ,

3 One of the consulting eogineer5, U. S. Bureau of Mines, and assistant mill superintendent, Walkermine concentrator,

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r .C.6555.

ORE TREATED

The Walker ore has complex mineralogical associations but may be classified as a gold and silver bearing chalcopyri te-magneti te-quartz ore. Recent examination of the ore by R. E. Head, chief microscopist of the United States Bureau of Mines, showed the approximate percentages of mineral constitutents to be as follows :

Quartz Garnet Chlorite Other nonopaque minerals Metallic minerals

Total

75.0 5.0 2.5 5.0

12.5 100.0

The metallic minerals, which as stated amount to 12.5 per cent of the ore, are dis­tributed as follows:

Magneti te ... Pyrite Pyrrhotite Minor metallic gangue minerals

Total metallic gangue minerals Chalcopyrite Chalcocite Minor copper bearing minerals Noncopper-bearing minerals

Total metallic ore minerals All metallic minerals

rer-f.ent~:Lyteight

59.76 7.80

1. 94 1.10

24.17 1. 60 2.55 1.08

70.60

29 .40 100.00

The ore is very resistant to crushing and fine grinding. During the spring months con­siderable difficulty is encountered in crushing operations due to the moisture content in

the ore. The tabulation which follows presents a chemical analysis of typical mill heads averaged

for a 6-month period.

Per cent Ounces_ruu:....ton

.QQ..QilllilrronlsulPhu.r/1:imell.nSQlUble Gold /~ilVtl 1.687 9.0 2.1 1.1 79 . 2 0.05 0.833

HISTORY

Milling operations began in June, 1916, with the completion of a 75-ton capacity pilot plant, which was erected at a distance of 4,700 feet from the shaft and at a much lower ele­vation. Transportation of the ore from the mine to the mill was accomplished by an aerial

tramway.

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Tripper

A Fine-ore bins

I I I I I I

Rougher T ,. l ! Cleane.. ",,::t";";' ~.

l , ;~ I I ' :,'"'

. "~:::.,.'.

U''«'=--~-.... ~-I:I*,;;,,~g;;::~:~.~~=...J;o!:: .," : ·~:1\:,. , • : Concentrates : " ":",

"". '[;""::lr~~ ~'~~: Middlings sump

Figure I.-Section of the Walker mine concentrator building

I. C. 6555.

The treatment of ore in this pilot plant may be briefly Rummarized as follows:

(a) The mine are was crushed to 2··inch size by Joshua Hendy crushers, one 12 by 24 inch and one 9 by 15 inch.

(b) . The crusher product was ground to 4 per cent plus 48-mesh in two No. 64t Marcy ball mills, each operated in closed circuit with a 4-foot 6-inch by l5-foot 9-inch Don

classifier, (c) The classifier overflow pulp, Which con t a ined 42 per oent of solids, was elevated

a distance of about 60 feet to the flotation di1.'ision, comprised entirely of sloping bottom Callow cells.

(d) The flotation concentrates '.yere partially deYlatered by two Callow cones, further thickened in a Dorr thickener and fi~tered by one 6 by 8 foot Oliver filter.

(e) The tailings were discharged ~nto a canyon and no attempt was made to recover water except that contained in the concentrates thickener overflow.

Power \'!as furnished locally by a steam plant of 350-hp. capacity until 1917 Vlhen electric power was made available by the completion Of a power transmission line 14 miles long by the Great Western Power Co.

Reagents used in the pilot mill were lime, coal tar , and pine oil. Coal tar was re­placed by thiooarbanilide in 1922.

During the operation of the pilot plant the International Smelting Co. aoquired an interest in the property and, in addition to securing eleotrical power previously mentioned, drove a working tunnel 1 mile long for the purpose of developing the mine 1,000 feet verti­cally below the outcrop. This tunnel was also oonnected with the upper workings and sinae 1922 has served for transporting mine ore to the mill, the aerial tramway formerly used for this purpose being abandoned.

In 1922 the size of ball-mill feed was reduced from 2 inches to 1 inch by the installa­tion of rolls. At this time the mill capacity was increased to about 300 tons of are per day.

A larger mine production neoessitated the building of a new mill of 750-ton capucity, which was completed and started to operate in December, 1923.

GENERAL DESCRIPTION OF PRESENT MILL

The present mill is built on a hillsirle a short distance from the portal of the main working tunnel. The location selected was well sui ted to standard mill construction and provided reasonable fall for gravity flow of pulp th rough the mill and down the valley to the tailings pond. The mill buildings are of steel and concrete with sides and roofs made of Anaconda corrugated zinc.

A typical longitudinal section of the concentrator building is presented in Figure 1. The ooarse and intermediate crushing plants are located in separate buildings at one

side of the mill proper. The mill proper includes four sections. Each seotion is equipped with a Marcy ball mill which operates in closed circui t with a Dorr classifier; these are followed by rougher, cleaner, and scavenger Callow flotation units. A thickening and filtering unit handles the combined flotation concentrates from the four mill sections.

On account of the isolation of the mine and mill , it is necessary to maintain well­equipped machine, electrioal, blacksmith, and carpenter shops. These shops can meet almost any emergency, which insures continuity of operations.

The mill as first designed, with three No . 75 Marcy ball mil ls and three flotation sec-· tions, was operated for some time at the rate of 750 tons of ore per day. Grinding during

10075 - 3-

I.C.6555.

this p&riod was maintained at 4 per cent plus 48-mesh size . The mill capacity was later in­creased to 1,200 tons per day by changing the degree of grinding previous to flotation treat-ment from 4 to 14 per cent plus 48-mesh size. It might be interesting to note that the small sacrifice in recovery entailed by coarser grinding was more than offset by the lower c~st of milling which resulted from the larger tonnage treated.

In September, 1929, the capacity was further increased from 1,200 to 1,700 tons per day by the installation of a fourth mill section. This lutter section is identical with the three original sections except that the grinding unit is larger ard comprises a No. 77 Marcy ball mill followed by a suitable classifier; (he larger grinding mill accounts for the addi­tional 100-ton ore capacity of this section .

Water Supply

Fresh water is obtained from springs and from the mine. The spring-water supply amounts to approximately 100 gallons per minute but th:Ls water is only available for mill use after camp requirements are satisfied. Water is pumped from the mine at the rate of about 300 gallons per minute, and this source provides the chief new water supply for the mill. The only water reclaimed from milling 'operations is that from the concentrates de­watering division. This amounts to approximately 60 gallons per minute and is returned to the supply tank located above the mill, where it is mixed with the fresh water .

J:Q.Y!..§L

The Pacific Gas and Electric Co. furnishes power to the mine and mill transformers from Caribou through its Veramont sUbstation at 22,000 volts. Mo to rs of 100 hp. or larger are operated at 2,200 volts and smaller motors at 440 volts. A 1l0···volt circuit is used for lighting.

PRESENT METHOD OF CONCENTRATING

A flow sheet of the crushing plant and ooncentrator with a legend which gives details of machines used is presented in Figure 2.

Qoars~ru.§.hing

Longi tudinal sections of the coarse and intermediate crushing units are given in Figure 3.

Ore is hauled from the mine to the crushing plant during three shifts. Ore trains which comprise eleven 3t-ton capacity side dumping cars are drawn by 35-hp. Baldwiil-\\'esting~

house electric locomotives. The ore is dumped onto a sloping steel rail grizzly having 11-inch spaces and after passing through the grizzly falls into a 1,500·-ton capacity, cylindri­oal, steel receiving bin.

Ore is drawn from this bin by a motor-driven, 42-inch, Anaconda-type pan. conveyor which discharges cnto an inclined grizzly having It-inch spaces. The oversize is fed to a Traylor crusher set at 3t inohes. The crusher is 15 by 24 inoh size, is driven by belt from a 150-hp. motor and will handle 85 tons of material per hour.

The grizzly undersize drops directly onto an inclined 2~ -inch conveyor belt and provides a cushioilir,g layer for the crusher product which drops onto the same belt . This belt is driven by a 15-hp. motor and delivers the are to the intermediate crushing uni t passing under an electromagnet enroute for the removal of tramp iron. A picker is stat .ioned at th:L:;; oon­veyor for the removal of wood,

1 t:

2

3

() ()4

Mine weier

/ Spring watw

/

24 35

31 To taillnp pond

~----~--j-~------~~34

Concentrates removed once a month

iO ~

43

cnl 38, 39 ~

Flaure 2.- Flow sheet of crushing plant and concenlratof

I.C.6555.

1~nd for flowsheet of crushing ~lant and concentrator

Number 1 ~ Description of machine~s~~ ____ ~ __ ~_~ ____ ~~ __ ~ __ ~

1 Track from m~ne.

2 One grizzly, II-inch spaces.

3 Ore bin, 1,500-ton ' capacity.

4 One pan conveyor, 42-inQh.

5 One g;rizzly, It-inch spaces.

6 One Traylor jaw crysher, 15 by 24 inch.

7 Belt conveyo r , 20-inch.

8 E~~c tromagnet.

9 One grizzly, It-inch spaces.

10 Two Anaconda jaw crushers, 8 by 20 inch.

11 One bucket elevator, 16-inch.

12 One trommel screen, It-inch holes.

13 One set Anaconda rolls, 24 by 55 inch, set at I-inch.

14 Two trommel screens, I-inch holes.

15 One set Anaconda rolls, 24 by 55 inch, set at t inch.

16 One bucket elevato~, 16-inch.

17 One pelt cpnveyor, 20-inch.

18 One tr~pper conveyor.

19 fine-ore .b~n, 2.400-ton capacity.

20 Fou r feed conveyor belts, 18-inch.

21 Four M~rcy ball mills, three No. 75 and one No. 77.

22 Four scoop boxes.

23 Reagent , feeders.

24 Four Dorr duplex classifiers, three 6 feet by 18 feet 4 inches and one 6 feet by

23 f eet . 4 . inches.

25 One_ Galigl.ier sampler for .heads.

26 Eight Callow rougher flotation machines, two 3-fo6t II-pan units per mill section.

27 Four primary Callow cleaner machines, one 3-foot 4-pan unit per mill s~ction.

28 Four sf;lcondary Callow cleaner machines, one IS-inch hoppered-type unit per mill

section : 29 Two Callow scavenger machines, 3-foot 7-pan units.

30 One middlings sump, tank capacity 2,000 gallons.

31 Three Krogh pUlJl})s, 3-inch.

32 Two Do ~ r ~once~trates thickeners, 12 by 25 foot.

33 One Dorrthickener., 11 feet 4t inches by 46 feet.

34 One centrifugal ' pump, 3-inch.

35 Water storage tank, capacity 100,000 gallons.

36 One bucket elevator, 16-inch.

37 One Oliv_~r_. ~ilt~r, 12 by S foot . 38 One Oliver vacuum pump, 14 by S-inch.

39 One Olive r compressor, 9t by 8 inch.

40 One belt conveyor, 18-inch.

41 Concentrates storage bin, 290-ton capacity.

42 One Gal~gh~r automatic sampler for tailings.

43 One centrifugal pump, It-inch.

1 Refer to numbers of Figure 2.

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I, C. 6555. Intermediate .Crushing

Ore from the coarse-crushing unit is delivered onto an inclined grizzly having It-inch spaces. The grizzly oversize is fed to two 8 by 20 inch Anaconda-type jaw crushers. The grizzly undersize joins the crushed material and the combjned products are fed by a bucket elevator to one 40 by 72 inch trommel screen having It-inch diameter round holes. ThA ele­vator is driven by a 20-hp. motor and is equipped with buckets 16 by 8 inches in size. The trommel operates in closed circuit with a pair of 55 by 24 inch Anaconda rolls set with a I-inch spacing; the rolls product returns to the elevator which feeds the trommel. The trommel undersize is distributed tc two 40 by 72 inch trammels having I-inch round holes. These trammels operate in closed circuit with one pair of 55 by 24 i.nch Anaconda rolls, set at j inch, the rolls product being returned to the trommels by a 16-inch bucket elevator.

The trommel undersize product, minus I-inch sizA, comprises the feed to the grinding units and is conveyed to the 2,400-ton capacity fine-ore bin by a 20-inch belt equipped with a tripper.

The coarse rolls are driven by a 100-hp. motor, the two Anaconda crushers and the fine ro~ls by a 150-hp. motor, and the three trommels by a 10-hp. motor.

Grinding~lld Classifyi.n.g

As previously indicated the concentrator is divided into four units for grinding and flotation operations. The three original grinding units are each equipped with one No. 75 Marcy ball mill which operates in closed circuit with a Dorr duplex classifier 6 feet by 18 feet 4 inches in size. The fourth unit was, as previously mentioned added to increase the capaci ty of the original mill and is equipped wi th one No. 77 Marcy ball mill which operates in closed circuit with a Dorr Duplex classifier 6 feet by 23 feet 4 inches in size .

Each No. 75 Marcy mill is dr-i ven at a speed of 24 r. p. ill. by a 200-hp., 900 r . p. m., in­duction motor through a Falk herringbone-gear speed reducer. The No. 77 mill is also driven at a speed of 24 r.p.m. by a 200-hp . , 900 r p.m., synchronous motor through a Westinghouse­Nuttal speed reducer.

Ball charges carried in the Nos. 75 and 77 mills weigh 9 and 13 tons, respective~y, and are maintained by the daily addition of 4-inch forged steel balls. Ball consumption is 2.074 pounds per ton of are ground.

Shell and feed end liners ar~ of manganese steel, the shell liners being of the ship­lap type. Grate sections are of rolled chrome steel and ·have t-inch openings. The tabula­tion which follows gives the life of liner parts and the consumption of liners per ton of ore ground.

Life of liner parts and consumption of liners per ton of ore ground

ILife of liner, I Liner consumption, ____________________________ \ hours Ipounds~ton of ore

Shell liners .... .... .. ... .. .. .. 3,200 0.273 Feed end liners Grate bars .... Total

I 4,300 0.176 ._I--±...;sOO 0.176

I 0.563

The classifie rs used with the No. 75 grinding mills are set at a slope of 3t inches to the foot and are operated at a speed of 27 strokes per minute by 5-hp. motors. The classi­fier which serves the No . 77 mill is set at a slope of 3 inches per foot and is operated at al'$p'eed of 25 strokes per minute by a 5-hp. motor.

1.0075 - 6 -

I.C.6555.

Ore from the fine-ore bins is delivered to the center of each drum and scoop type ball­mill fee de r by an 18-inch conveyor belt . Each No. 75 mill receives feed at the rate of 16t

tons per hour and the No. 77 mill at the rat e of 23+ tons per hour. The grinding mills opera t e with an average circulating load of 145 per cent and with pulps containing from 77 to 78 per cent ~f solids.

The degree of grinding is maintained at 12 per cent plus 48-mesh; classifier overf low pulps contain from 46 to 50 per ~e~t of solids.

Table 1, page 9 presents sQr~ en analY 'l es of ball-miL\. feed and of intermediate and final grinding-circuit p!" oduct~ .

flot a tion r

For simplicity of control and metallurgical accounting the classifier overflow pulps o,f the four grinding sections are combined, sampled and then distributed equally to four flota­tion units. The equipment of e~ch flotation section comprises two 3-foot, II-pan, standard Callow rougher machin~s, one 3-foot, 4-pan, standard primary Callow cleaner, and one IS-inch, hoppered-type, secondary Callow cleaner.

The two r.ougher machines ope.rate in parallel ; rougher concentrates are removed from the first three pans and middlings froths from t he remaining eight pans . The rougher concen­trates, which have an av'erage content of 15 per cent of copper, are c,leaned in two stages, the final s tage producing finished concent rates. The middlings froths of the rougher machines join the tailings of the two cleaner cells and flow by gravity to a comm·on pump sump, and from there are returned to the head of the rougher cells by three 3-inch Krogh s and pumps, ea ch of which is driven by a 15-hp. motor.

The tailings from the roughe r cells of the four flotation sections are combined and dis­tributed to two 3-foot, 7-pan, Callow scavenger units which produce middlings froths and final waste tailings. The middlings froths joi n the middling~ o.f the rougher and cleaner uni ts in the common sump and are returned to the heaEls of i-he roug,hers.

Cell blankets of 4-p) y, quilted, 18-ounce canvas are used and have a life of from 60 to 90 days.

Air for flotation operations is furnished a t 4.15 pounds per square inch pressure by two No . 6t Roots bloweres and one Conners v511e blo wer. The Roots blowers are each link-belt driven at a speed of 172 r.p.m . by a 150-hp. motor. The Connersville blower is also link­belt driven at a speed of 240 r.p.m . by a 75-hp . motor.

The reagents used in flotation comprise lime, potassium ethyl xanthate (Z-3), and steam-distilled pine oil. Sodium aerofloat was used for a short period, bu,t recently its use has been dis c ontinu~d.

Dry hydrated lime is fed to the ball mills from s mall hoppered feeders at the rate of 1.2 to 1 . 6 pounds per ton of ore milled. These ~mounts produce a protective alkalinity of about 1 . 09 pounds of CaO per ton of milT wat e r which is sufficient to insure the desired metal 1 urgical resul ts . Operators are requi red to make hourly ti tra tions for protective alkalinity and to make immediately any changes in the rate of adding lime as indicated by these titrations.

Xanthate i s added as a 25 per cent solution to the clas sif~e I; ov",erftm'lt .pulPs bil' ' &

scraper .feeder at t,he rate of 0.18 pound per t on of ore treated. Steam-distilled pine oil is added to the ball mill s by a scraper feeder at the rate of

0.16 to 0.22 pound per ton of are. A rather large amount of this reagent is necessary on account of th e coarseness of the flotation feed and also due to the fact that flotation opera t ions are conducted in a circuit which i s essentially a fresh-water circuit.

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I. C.6555.

DE'!IATEPJNG AND HANDLING OF CONCENTRATES

The concentrates pulps which contain from 20 to 25 per cent of solids, flow by gravity to two 25 by 12 foot Dorr thickeners. The thickened pulps containing 75 per cent of so lids are de livered to one S by 12 foot Oliver drum-type filter by a 16-inch bucket elevator. The filter is chain driven by a 3-hp. motor. The concentrates produced are handled by operating the filter on two of the three daily shifts, one operator being required on each shift.

A vacuum amounting to 22 inches of mercury is maintained at the filter by one 14 by 8 inch Oliver vacuum pump which is driven by belt from a l5-hp. motor. Blowing air is fur­nished at 5 pounds pressure by a 9* by 8 inch Oli ve r compressor, driven by belt from a l5-hp. motor. The filtrate is handled by a It-inch centrifugal pump in place of the usual baro­metric leg. A filter cover gives approximately six months of service before replacement is necessary.

The overflows from the two Dorr thickeners are conveyed to a spare 45 by 12 foot thick­ener, where a small additional recovery of fine concentrates is made. These concentrates are allowed to accumulate and are dewatered in the filter ab6ut once each month.

The filter cake, which averages l to t inch in thickness and which contains from 8 to 10 per cent of moisture, is discharged onto a 14-inch conveyor belt and delivered by this belt to a 290-ton capacity storage bin. The concentrates are loaded from this storage bin into SOO-pound capacity tramway buckets; the latter are trammed to Spring Garden where the con­centrates are dumpeu -into railroad cars for shipment to the Tooele plant of the Inter­national Smelting Co.

The tramway is of the double rope type and is 9 miles long. The loaded side is equipped with It-inch locked-coil track cabl e and the light side with l-inch cable of the same con­struction. The buckets are equipped with automatic grips which engage a i-inch Lang Lay traction rope which is driven by a 50-hp. motor.

Labor Ellllployed on the tramway includes 1 foreman, 3 loaders, 3 unloaders, 2 line riders, and 1 agent, who is located at Spring Garden.

Since the completion of the aerial tramway in 1922, it has been an important factor in plant operation as it is the only means of transporting passengers, mine and mill supplies and camp provisions during the months of heavy snowfall.

DISPOSAL OF TAILINGS

The tailings of the scavenger fl otation cells contain from 33 to 36 per cent of solids and are conveyed by a wooden launder for n distance of about % mile to a large impounding pond. Proper precau t ions are taKen to prevent tailings from entering near-by streams .

MILL SAMPLING

Samples of the heads as represented by the combined classifier overflow pulps, the con­centrates, and the final tailings are t~ken during each shift by Galigher automatic samplers. The samples are dewatered in a sm&ll pressure filter and after being dried are split to convenient-size assay pulps.

An analysis for copper content is made on each shift sample for mill guidance and control. A composite sample is made from shift samples for metallurgical accounting. These composite samples are assayed for copper, gold, silver, and insoluble contents.

Cars of concentrates are sampled by pipe samplers at Spring Garden before being shipped to the smelter.

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I.C.6555.

METALLURGICA~ 4N~ QPERATING DATA

Screep analyses of concentrator intermediate and final products are presented in Table 1. Table 2.l gives chemica1 "analyses of mill heads, final concentrates, and tailings; and Table (3

shows the percentage distributions of copper, silver, gold, iron, and insoluble in fina] concentrates and tailings. MetallUrgical data for the period June to November, 1930, are presented in Table 4, and the distribution of labor is 'shown in Table 5.

Table 1.- Screen analyses of concentrates intermediate and final-QrQducts

We~~.LQent

...... " .- No. 75 Marcy mill units NO.77 MarcLmill unit Flotation products Screen. size BalJ.- Ball-

Iclas-Clas-

Ball- mill Clas- Clas- mill sifier mill dis- sifier sifier dis- sifier over- [concen-[Midd1ings/Tail-

g! feed charge .§.ands Qverflow cha.IK~ sand!L .f~ t ra tf.!L ___ ~ in..&.!L Plus l :.inch 5.4 Plus t ; inch 41.3 1.4 0.9

Plus . 4-mesh 23.0 2.6 8 . 1 1.2 4.7 Plus 8-mesh 9.5 4.7 8.5 2.5 6.0 Plus 30-mesh 9 . 0 30.0 43.5 2.5 23.8 46 . 5 2 . 2 3.2 Plus 48-mesh 1.8 14 . 0 14.8 11.2 14.3 15.4 10.5 4.8 3.0 15.7

Plus 65-mesh 2.9 8.1 6.4 22.4 11.4 8.4 14 .6 6 . 8 1.5 5 . 5

Plus 100-mesh 0.5 6.8 3.3 2.5 7.0 3.3 6 . 2 18.1 4.5 13 . 8 Plus 150-mesh 2 .4 J 6 , 0 3.8 15.5 10.5 4.2 9.0 14 . 5 4.4 10 . 0 Pl us ZOO-mesh 2.9 6.1 3.7 2.3 6.5 3.3 12.2 6.8 6 . 0 10.7 Minus 200-mesh ~[~~ 43.6 22.8 -1.;.~ .A~ ~lLJL --~ .ALl Totals 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

"T

Table 2.- Chemical analyse!L.QLmilLru:.Qduc ts, June to November,,--l~30

I . Analyses . ____ ._

Copper, J Silver, I Gold, Insoluble, Iron, Weight,

~§1nt

100.0 6,41

93.59

~r cent ounces pgLton ounces ~LtO!l 1.687 0 . 833 I 0.05

_P§1.LQf.n:L ~ eni 79.0 9.0 Heads ... " .. " ...

Concentrates Tailings

24,00 9 . 920 0 . 49 14 . 5 22.1 0.163 0.200 0 . 02 83 . 5 8.1

Table 3.- Mill recoveries and losses, June to Novembs~QQ

I Weight, ___________ I-2f.r cen t

Concentrates Tailings --------------.

10075

I 6 . 41

93.59

I Distributions~er ce~n~t_~ ____ __

I~~ I_§UVSL 1~1£L Jns olublL -.l..I21L

j 91.2 f 73.3 I 62.7 1.2 15.8 8.8 23.7 37.3 98.8 84.2

... 9 -

I,,£:., 9~Q9 ., _

Table 4 ,- Metallyrgical data, June to Novembe~ 1930

Ore treated, total .... ...... .. ...... .. .. .... .. .. .. ... ... .......... ... ..... .. ... ..... .. .. .... .. ...... .. ~ .. .. Days operated ............ .. ....... .. ... .... .... .. , .... .. .... .. .. .... ... .. ... .... ..... .... ... ..... .. ..

tons

'/ number Operating time per day . .hours . Amount of ore treated per .24 hours, average tons ' . Ore tree.ted per man-shift per 24 hours, average " do

number 24 hours, _ aver~ge:

fections operated, average Ore t reated per section per

,No._ 75 .Marcy mill. uni ts

_ ~o :..:!'!. ~~r:.?y_ !ll~l} uni t Concentrates produced, total Copper produced, total

".:. ' "-"~'" " .: "" . ".''' :..::. '' " . ' : ' ." ": '. .~ .. ~~ ' .. '''' ' ,: .. ~ . .:. ~ - ~ <2Il? _. _I

• •• ••••• • • • • • ••• •• •••• : .. • • • • •• • •• • • •• • • • '. ~' • !-=.. ' • ' :' .:< ~ :.!.~.! :,.' • l.l..' . .:....:..,

.. - .. .. ~ . . ': . . . ~ ..... .. ... . ' ... , ..... ...... . ',: ... . .

Concentrates produced pe r 24 hours , average Recoveries:.

Copper Silver Gold .....

Ratio of concentration Pressure of flotation air, per square inch AlKalinity of mill water, CaO per ton of water

, ..... £to ..... d\;>

pounds tons

per, cent do do

tons into 1 pounds

do PIlls . 48-mesh material in flotation tailings .............. per cent Consumptions of wate r, reagents. and supplies per ton of ore milled:

10075

Net water used ........ .... .. .. . .. ... ... . gallons Lime Pine oil Potas sium ethyl xanthate (Z-3) Sodium aerofloat (u s e discontinued) Balls

Liners

- 10 -

pounds do

49 do db do

268,21)5 169.67 ' ..

24 1 ; 580.62

. 38.51

3.84

~90

500 17,290.54

84,027,948 101. 90

k11.21 .. 76.32 .62.73. 15 . 57

4 . 15 1.09

lL10

325 to 350 1.40

. 0 . 321 0.084 0.075 2.074 0.563

10075

Table 5.- Distributi on of labo r

lNumbeLilltr 24~J!£§ Mill superintendence:

Mill superintendent Shift foremen

Coarse and intermediate crus hing departments : Crusher operators Crusher helpers Rolls .... ... . ..... ........ ..... . ..... .... .. ..... .. Screens .... ........ , . .... ......... .. .. ..... .... ...... .... ... ... .. .. Electromagnet .... .... . .... ... ... .... ... ...... .... .. .. .. .. ... ..

Grinding and flotation department s : Ball mills Flotation operators ....... .... .... .. .. .. .. ... .. Flotation helpers .. .. ..... ... .. .... .

Filter department: Operators "" "

Repair and shop crews: One repair foreman and 20 men

,I

Distribution of electri c-2Qwe~

May. 1931

Department Kilowatt-hours ~§.~1 Primary crushing 42,804 7.22

Secondary crushing 42,804 7.23

Grinding 348,631 58 . 83

Flotation 149,765 25 . 27

Fil tration 8,561 1.45

Totals .... .. .... .. .. .. .. .. . 592,565 100.00

- 11 -

1

3

2

2

2

2

2

3

3

3

2

21

I.C.6555.

To interrn.... . "­"V'a,,, crUShing Units

NOTE: This section is .approximately at a right angle to the grinding sections

o o : '

Conveyor from primary ~. crushing unit

ilf~e t,tl ~~Anaconda jaw crusher

d Ore Ore

INTERMEDIATE CRUSHING UNIT

Figure 3.- Longitudinal sections of the coarse and intermediate crUShing units

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