MANGANESE MINING AND MILLING

METHODS AND COSTS, MOHAVE

MINING A:ND MILLING CO.,

MARICOPA COUNTY, ARIZ.

By P. V. Fillo

r + + r r r r i r r r information circular 8144

UNITED STATES DEPARTMENT OF THE INTERIOR Stewart L. Udall, Secretary

BUREAU OF MINES Marling J. Ankeny, Director

This publication has been cataloged as fol lows:

Fillo, Paul V Manganese mining and milling methods and costs, Mohave

Mining and Milling Co., Maricopa County, Ariz. [Washingtom] U. S. Dept. of the Interior, Bureau of Mines [I9631

ii, 29 p. illus., tables. 26 cm. (U. S. Bureau of Mines. Infonna- tion circular 8144)

1. Manganese mines and mining-Arizona. I. Title. (Series)

TN23.U71 no. 8144 622.06173

I U. S. Dept. of the Int. Library

MANGANESE MINING AND M I L L I N G METHODS AND COSTS, MOHAVE MINING AND M I L L I N G CO.,

MARICOPA COUNTY, ARIZ.

INTRODUCTION AND SUMMARY

This paper describes Mohave Mining and Mill ing Co. methods of mining and m i l l i n g manganese ore i n Arizona. It i s one of a s e r i e s of publicat ions pre- pared by t h e Bureau of Mines on methods and cos t s i n various mining d i s t r i c t s i n the United S ta tes .

Production of manganese ore, a s such, i n Arizona began i n 1915. Before t h i s time manganiferous ores had been mined primari ly for s i l v e r content and used as a smelter f lux . From 1916 t o 1918 approximately 69,000 long tons of manganese and nclanganiferous ores were mined. Af ter World War I production dropped t o almost nothing u n t i l World War 11, during which period more than 24,000 long tons were produced. A l u l l i n manganese mining occurred a f t e r World War 11, having production r a t e s of only a few hundred tons annually through 1952.

I n January 1953 under the Defense Production Act, General Services Admin- i s t r a t i o n (GSA) s e t up a manganese-purchasing depot a t Wenden, Ariz. Under t h i s purchase plrogram, domestic mater ia l containing not l e s s than 15 percent manganese was purchased a t p r i ces based on $2.30 per long-ton u n i t for 48 per- cent recoverable manganese. A s imi la r manganese- purchasing depot was es tab- l i shed i n November 1951 a t Deming, N. Mex. This incent ive program provided a market and shig~ments increased. The program quota was f i l l e d i n about two years. During t h i s period a t o t a l of 403,744 long tons of manganese ore was shipped t o t h e two depots, and 113,428 long tons of concentrates was shipped t o the Deming clepot. The Wenden depot was closed May 10, 1955, a f t e r reaching i t s prescribed quota, and the Deming depot was closed November 19, 1955, upon f i l l i n g i t s quota.

As the re tras no longer a s u i t a b l e market f o r mate r i a l containing l e s s than 40 percent: manganese, most of t h e mines were forced t o c lose down or r e s o r t t o some means of benef ic ia t ion . Custom mi l l ing became important a f t e r

'work on manuscript completed May 1962. a ~ o r m e r mining engineer, Division of Mineral Resources, Bureau of Mines,

Tucson, A r i ; ~ , ; now with Office of Minerals Exploration, San Francisco, C a l i f .

t h e purchasing depots were closed; output of o r e and concent ra te was shipped under the "car lo t" program administered by G.S.A. Custom ores of a manganese grade high enough fo r d i r e c t shipping but conta in ing too much llead and z inc were handled by Mohave Mining and Mil l ing Co. by s i n t e r i n g a f t e r crushing and s i z i n g i n a small crushing p l a n t a t t h e company's p l a n t .

Shipments were accepted by t h e Government i n l o t s of one o r more carloads, l imi t ed i n e f f e c t t o l e s s than 10,000 long dry tons per calendar year per opera tor . A f i rm p r i c e of $2.30 per long dry- ton u n i t was paid fo r o r e con- t a i n i n g 48 percent manganese, w i th premiums o r p e n a l t i e s fo r v a r i a t i o n s i n a n a l y s i s . The program quota was completed, and t h e program was terminated on August 5, 1959, i n so fa r a s new commitments were concerned.

Most of t he mining was done from opencut workings using heavy, d i e se l - powered earthmoving equipment, bu t some o r e was produced by underground mining methods.

An attempt has been made t o ob ta in cos t da t a fo r manganese product ion from the owners and t h e l a r g e r ope ra to r s . Operating records were a v a i l a b l e only from one company, Mohave Mining and Mi l l ing Co., and these were not a v a i l - a b l e fo r a l l periods during the l i f e of t he company. However, round f igu res were obtained fo r two o the r opera t ions .

The a c t i v i t i e s of Mohave Mining and Mi l l ing Co. were q u i t e v a r i e d during i t s l i f e . I n add i t ion t o o r e from i t s own mines, inc luding t h e Black Rock, t h e company mi l l ed crude o r e and s i n t e r e d concent ra tes and o r e from more than 225 d i f f e r e n t producers. During t h e f i r s t h a l f of 1960 Mohave Mining and Mil l ing Co. c losed down and disposed of i t s s i n t e r i n g p l a n t and much of i t s m i l l i n g Guipment .

Inves t iga t ion fo r t h i s r e p o r t was begun i n September 1959 and completed i n J u l y 1960, During t h i s period no s i g n i f i c a n t mining was repor ted . The s i n t e r i n g p l a n t processed o r e shipped from Mexico u n t i l i t was c losed i n January 1960. Complete engineering da ta and c o s t records were no t a v a i l a b l e .

This paper gives a b r i e f h i s t o r y of Black Rock mine, whose opera t ing records were r e l a t i v e l y complete; descr ibes t h e genera l geology of i t s o r e depos i t ; and o u t l i n e s methods of exploring, sampling, developing and mining ( including d r i l l i n g and b la s t ing , loading, and t r anspor t a t ion ) . Production r a t e s , s a f e t y p rac t i ces , and supervis ion a r e described b r i e f l y . Mi l l ing and s i n t e r i n g opera t ions and c o s t s a r e discussed.

ACKNOWLEDGMENT S

The author i s indebted t o t h e management and s t a f f of Mohalve Mining and Mil l ing Co. fo r t h e i r cooperat ion and a s s i s t a n c e i n prepar ing t h i s r epor t , and fo r t h e i r permission t o publ i sh t h e ma te r i a l contained he re in . Specia l acknowledgments a r e g r a t e f u l l y extended t o H. F. Lynn, p re s iden t ; W . R. Eas ley, genera l manager; Tom Saunders, m e t a l l u r g i s t ; M. L. Pate, mine super- in tendent ; R. F. Monnahan, s i n t e r p l a n t super in tendent ; and L. W. Whitney, mine geologis t ; who gave t h e i r time and a s s i s t a n c e f r e e l y .

CONTENTS

In t roduct ion and smnnary ................................................. 1 Acknowledgments .......................................................... 2 Location and ph, y s i c a l f e a t u r e s ........................................... 3 His to ry .................................................................. 4

.................................................. Descr ip t ion of depos i t s 4 . ................................................. Explora t ion and . sampling 5 -

=ning ...................m...mm.................m..........m............. 3 ................................................ D r i l l i n g and b l a s t i n g 7 Open-pit opera t ion ....~........................................ 7 ............................................. Underground mining 10 .......................................... Loading anid t r a n s p o r t a t i o n 11

Production .......................................................... 12 ................................................... Mine organ~iza t ion 12 .................................................. Mine su r fa~ce p l a n t 13 ..................................................... Safe ty prarctice 13 ............................................................ Concentrat ing 14 ........................................................ 0rganizati .on 14 . . Power and water ..................................................... 13 Ore treatnlent ....................................................... 17 ................................................................ S i n t e r i n g 24

Mining and millling c o s t s ................................................. 26

ILLUSTRATIONS

F i a . 1 . Location map. Mohave Mining and Mi l l ing Co . proper t ies . Maricopa

and Yavilpai Counties. Ariz ........................................ 3 ............................... Geologic p lan and s e c t i o n of o r e body 6 ............... Plan and s e c t i o n of open-pi t abd underground workings 8 Plan and s e c t i o n of su r face d r i l l i n g p a t t e r n .............Om........m 9 Wagon driIL1 mast mounted on front-end loader ........................ 10 Diagram o:E water d i s t r i b u t i o n ....................................... 16 Flowsheet of crushing s e c t i o n ....................................... 20 Flowsheet of g rav i ty s e c t i o n ........................................ 21 Flowsheet of f l o t a t i o n and reagent s ec t ions ......................... 22 A e r i a l photo of t h e m i l l a r e a ....................................... 23 Flowsheet of s i n t e r i n g p l a n t ........................................ 26 A e r i a l photo of s i n t e r i n g p l a n t a r e a ................................ 27

TABLES

Page

Explosives characteristics and loading data...............e.m.memmm. 11 Black Rock mine production data (long dry tons) . . . . . . . . . . . m e . . . e m m . . 12 Average mine crew...................,......................~........ 13 Wage rates in 1958.. . . . . . . . . . . . . . m . . m . . . . m . . . . . m m m . . m . . . m . . . . m . . . . m . 13 Inventory of major mining equipment ...........m..m.........e~...mmm. 14 Mill crew by shifts................................................. 15 Mill labor distributi~n........~.........~.~.~~~.~....~..~....~.~~~. 15 Mill power distribution............................................. 16 Inventory of milling equipment .............m~.a.m.m.m...mm..m...e... 17 Summary of open-pit mining cost^....................^.....^^...^..^. 28 Distribution of milling costs, percent.............................. 28 Average processing cost~..~...........,~~.~....~....~.~.~~....~...~. 29

LOCATION AND PHYSICAL FEATURES

The Black Rock proper ty i s i n ~ 1 / 2 sec . 34, T. 5 N., R. 9 W., Gi la and S a l t River base and meridian, Maricopa County, Ariz ., 21.0 mi les south of Aguila--a branc:h- l i n e s t a t i o n of t h e Atchison, Topeka & Santa Fe Railway. Aguila i s on U. ,S . Highway 60-70, 27 miles west of Wickenburg and 22 miles e a s t of the Government manganese s t o c k p i l e a t Wenden, Ariz. The property i s reached from Aguila by d r iv ing south on an improved d i r t road 15 miles, tak ing a l e f t fork f o r 16.5 miles, and taking another l e f t fork fo r 21.0 miles t o the proper ty ( f i g . 1).

FIGURE 1. - Location Map, Mohave Mining and Mil l ing Co. Properties, Maricopa and Yavapai Counties, Ariz.

Topography of the region i s of moderate r e l i e f (low f o o t h i l l s ) bordering the nor thern f lank of the Big Horn Mountains, wi th a l t i t u d e s ranging from 2,300 t o 2,600 f e e t above sea l e v e l . The c l imate i s a r i d , and t h e reg ion supports only spa r se dese r t vege ta t ion . Water was obtained from a few shallow we l l s along the broad v a l l e y t h a t bounds t h e d i s t r i c t on t h e no r th and west .

The m i l l , about 48 miles from the mine, was approximately 4 miles north- e a s t of Wickenburg, Ariz . on t h e nor th f lank of t h e Hassayampa r i v e r i n sec . 14, T. 8 N., R . 5 W., i n Yavapai County. The s i n t e r i n g p l a n t was bes ide t h e r a i l r o a d i n sec . 19, T. 8 N., R . 5 W., approximately 7 miles nor th of Wicken- burg, and 1 /2 mi le west of U.S. Highway 89 ( f i g . 1) a l s o i n Yavirpai County.

The Black Rock proper ty comprises e i g h t unpatented claims. Three of t h e claims were loca ted i n 1916 and a t t h a t time were known a s t h e Black Warrior group. Some mining was done before 1952, but no records a r e a v a i l a b l e of t h e o r e shipments. The claims were r e loca ted by J . N . House of Aguila i n 1951 a s Black Rock Nos. 1, 2, and 3. Claims 1, 2, and 3 were acquired by A . R . Bue l l of Aguila e a r l y i n 1952, and an explor ing and mining opera t ion was s t a r t e d i n March of t h a t year . A t t h e end of March 1954 about 3,000 tons of o r e contain- i ng 30 t o 35 percent manganese was shipped from Claim 1.

Black Rock No. 3 claim was explored by shallow p i t s and opencuts, and dur- i n g 1953 l e s sees shipped seve ra l hundred tons of m i l l o r e from these excava- t i o n s . In Apr i l 1955, claims 1, 2, and 3 were purchased from A, , R . Buel l by Big Horn Wining Co., and t h i s company loca ted f i v e a d d i t i o n a l claims.

DESCRIPTION OF DEPOSITS

The p r i n c i p a l manganese mineral a t Black Rock mine i s r a m ~ c l e l l i t e , ~ a manganese oxide (Mn0,) c r y s t a l l i z i n g i n t h e orthorhombic system,. Minor amounts of psilomelane-type manganese oxide occur along f r a c t u r e s . The gangue i s com- posed l a r g e l y of unreplaced hos t rock and minor s t r i n g e r s of c a l c i t e and qua r t z .

Geologically, t h e a rea i s composed of a basement of Precambrian gneiss ove r l a id by Cretaceous volcanic rocks t h a t a r e p r imar i ly b a s a l t but conta in minor amounts of andes i t e . Light-colored t u f f , agglomerate, ancl flow b recc ia a r e a l s o present . The o r e body i s on o r near t h e contac t of the volcanic wi th t h e basement rocks. Near t h e o r e body t h e contac t s t r i k e s N. 6CI0 W. and d ips 25" SW. The underlying rocks a r e s t rong ly sheared and a l t e r e d ; some v e r t i c a l and h o r i z o n t a l movement has occurred along t h e contac t .

The o r e body i s a l e n t i c u l a r replacement of t h e tuffaceous ma t r ix of t h e agglomerate and o v e r l i e s t he gneiss . In some p laces t h e agglomerate i s sepa- r a t e d from the gneiss by bedded t u f f . 3 Farnham, L. L., and Stewart , L. A., Manganese Deposits of Western Arizona:

Bureau of Mines Inf . Circ . 7843, 1958, 87 pp. 4Max D. Crit tenden, Jr., U.S.G.S., i n l e t t e r t o L. E . Whitney, company

geologis t .

East of t h e open p i t t h e agglomerate grade changes i n t o a flow brecc ia , minera l ized by. manganese-oxide f i l l i n g s of t h e b recc ia i n t e r s t i c e s and frac- t u r e s . The average th ickness of t h e mined o r e body was about 25 f e e t , and length along t h e s t r i k e was about 625 f e e t . The o r e was followed 450 f e e t downdip from the outcrop ( f i g . 2) ,

Severa l small f a u l t s s t r i k i n g N . 30' W. cu t both t h e o r e body and t h e underlying gne.iss. Most of t hese f r a c t u r e s d i p 50' t o 80' NE; a few dip south- west . The displacement of t hese f a u l t s ranges from a few f e e t t o a s much a s 25 f e e t , bu t f a u l t i n g r a r e l y has caused d i s c o n t i n u i t y of t h e o r e body.

EXPLORAT ION AND SAMPLING

Exploratalry work was done e n t i r e l y by wagon d r i l l s ; t h i s method was found t o be t h e chea.pest when explor ing shallow depos i t s . To o u t l i n e t h e deposi t , ho le s were d r i l l e d by Mohave Mining and Mil l ing Co. on a 60- foo t g r i d p a t t e r n using t h e s t r i k e of t h e o r e zone as a base l i n e ; some holes were over 100 f e e t deep. D r i l l i n g was stopped when t h e Precambrian gneiss was reached. The loca t ion of ea.ch d r i l l hole, th ickness of overburden, and th ickness and grade of o r e were p l o t t e d on a map. This furnished engineering information from which t h e mining method was determined.

The d r i l l c u t t i n g s were caught i n a box surrounding t h e c o l l a r of t h e ho le . Samples were taken a t 5-foot i n t e r v a l s from the c o l l a r of t he d r i l l ho le t o t h e top of t h e o r e zone fo r v i s u a l i n spec t ion t o determine the type of rock. A compc~site sample of t h e 5- foo t runs was taken fo r ana lys i s when min- e r a l i z a t i o n was evident . In t h e o r e zone the d r i l l c u t t i n g s f o r each 5-foot run were coned1 and quartered, and t h e r e s u l t i n g sample was assayed,

Mining op~era t ions were cont rac ted wi th Big Horn Mining Co. which l a t e r subcontracted t h e mining t o M , L. Pate . One of t h e mines of Mohave Mining and Mil l ing Co. wa.s Black Rock mine. Farnham and s tewar t6 descr ibe the Black Rock mine before Big Horn Mining Co. tenancy, a s follows :

h he p r i n c i p a l v e i n on (Black ~ o c k ) claim NO. 1 was developed by an i n c l i n e d s h a f t , 50 f e e t deep, and a s i n g l e l e v e l from the bottom of the s h a f t t h a t followed t h e v e i n f o r about 400 f e e t . Stopes, ranging from 50 t o 100 f e e t i n length. and averaging about 5 f e e t i n width, extended t o var ious he igh t s above t h e l e v e l . The o r e was mined i n open s topes supported by s t u l l s and p i l l a r s of lower g r a b o re . B l a s t holes were d r i l l e d with jackleg- type rock d r i l l s . The ore, when b l a s t e d i n t h e back of t h e s topes , f e l l t o the f l o o r of t h e l e v e l . A scraper , powered wi th a double-drum s lushe r h o i s t , was used t o p u l l t h e broken o r e t o the bottom of t h e s h a f t , where i t was shoveled i n t o t h e s k i p , Aft.er t h e o r e reached t h e sur face , i t was placed i n p i l e s near t h e c o l l a r of t h e s h a f t ; i t was then hand-sorted and loaded i n t o t rucks wi th a small power sh~ovel .

6 ~ o r k c i t e d i n footnote 3 (p. 4 ) ) pp. 19-20.

BLACK ROCK NO. I I

FAULTS

ORE

SECTION A-A'

TUFF pfl + + + BASALT

FIGURE 2. - Geologic P lan and Section o f Ore Body.

I 1 The west v e i n on t h e Black Rock NO. 3 claim had been explored i n s e v e r a l p l aces by shallow p i t s and opencuts. The most ex tens ive opening was an open- c u t about 100 f e e t long, 2 t o 4 f e e t wide, and about 8 f e e t deep ."

A t f i r s t t h e overburden was removed i n 18-foot benches downdip along t h e s t r i k e of t h e o r e body. When t h e depth of the overburden became too g rea t f o r t h e normal opera t ion of wagon d r i l l s , a r o t a r y d r i l l was used. This machine was used t o d r i l l 50-foot 4-314-inch b la s tho le s , and the l & f o o t waste benches were el iminated. On completing t h e r o t a r y d r i l l i n g and t h e s t r ipp ing , t h e o r e body was s u f f i c i e n t l y exposed t o a s su re an adequate o r e r e se rve f o r t h e mining program. A s mining progressed i n t h e s t r i p p e d a rea i t was decided t h a t f u t u r e mining would be done underground because of t h e th i ck overburden. When the s t r i p p i n g opera t ion was concluded, a room- and- p i l l a r method was employed, us ing double-,drum s lushe r h o i s t s ( f i g . 3 ) .

D r i l l i n g and B las t ing

Open- P i t Operat ion

A t t he s t a r t of t h e open-pit operat ion, overburden d r i l l i n g was done wi th wagon d r i l l s ,, The 1- 114- inch round d r i l l s t e e l was used i n 10- foot s ec t ions . D r i l l ho les were c o l l a r e d wi th 3-inch-diameter s t e e l c ros s b i t s and f in i shed wi th 2- 112-inch-diameter b i t s . D r i l l crews cons is ted of two men. Compressed a i r was suppl-ied by one 600- c . f .m. and one 315- c . f .me r o t a r y compressor.

Much of the d r i l l was i n f r ac tu red and b recc ia t ed rock, and d r i l l b i t s o f t e n were l o s t . By experimental d r i l l i n g , i t was found t o be cheaper t o use s t e e l c ros s b i t s than the more expensive ca rb ide - inse r t b i t s .

Blasthol-es were spo t t ed by t h e p i t foreman. Two rows of holes were d r i l l e d p a r a l l e l t o the c r e s t of t h e previous c u t . Rows were spaced 6 f e e t apa r t , and the holes were 10 t o 12 f e e t a p a r t . Spacing of t he d r i l l ho les depended upon t h e cha rac te r of t he ground and whether o r no t t he face of t h e lower bench had been c l ea red of broken ma te r i a l ( f i g . 4) . D r i l l i n g speed of t h e wagon dri-11s ranged from 15 t o 20 f e e t pe r hour. The benches usua l ly were 18 f e e t high, , Blas tholes were d r i l l e d 2 f e e t deeper than bench he ight t o a s s u r e a reasonably l e v e l p i t f l o o r fo r t h e heavy equipment opera t ion .

Later Mohave Mining and Mil l ing Co. cont rac ted fo r 8,500 f e e t of 4- 314- inch, ro tary- d r i l l e d b l a s tho le s . I n t h i s d r i l l i n g program ho le spacing was 20 f e e t i n rows 10 f e e t apa r t , wi th s taggered holes . The average depth of d r i l l ho le s was 54 f e e t .

Free flowing quarry-type dynamite was used t o b l a s t and break the over- burden. The type used has a low v e l o c i t y t h a t produces a heaving r a t h e r than a s h a t t e r i n g e f f e c t on the overburden. Approximately 75 percent of t h e d r i l l ho le was f i l l . ed wi th dynamite, and the remaining 25 percent was f i l l e d with stemming ( d r i l l c u t t i n g s ) . Millisecond-delay e l e c t r i c b l a s t i n g caps were i n s e r t e d i n EL 1-118- by 8-inch c a r t r i d g e of dynamite t o form the primer used t o de tonate t h e charges. Approximately 0.5 pound of explosive w a s used for

each ton of cmerburden b la s t ed .

BANK TOE7

BANK CFIEST7

SECT ION A-A'

\\ 3" dri holes

SCALE, FEET

FIGURE 4. - P lan and Section of Surface D r i l l i ng Pattern.

A modified wagon d r i l l was used fo r d r i l l i n g t h e ore . Blas tholes were d r i l l e d by a 4-inch pneumatic drill on a 12-foot mast. The mast w a s attached t o a f ront - end loader mounted on a crawler t r a c t o r ( f i g . 5) . The u n i t proved

FIGURE 5. - Wagon D r i l l Mast Mounted on Front-End Loader.

t o be v e r s a t i l e and e f f i c i e n t . Compressed a i r was suppl ied by one 315-c.f.m. r o t a r y compressor. The b i t s , d r i l l s t e e l s , and d r i l l p a t t e r n s were the same a s those used on the overburden. Ore benches ranged from 5 f e e t t o a maximum of 18 f e e t high. The same types of quarry dynamite and b l a s t i n g caps used i n the overburden were used i n t h e o re . The powder' f a c t o r was approximately 0.7 pound of explosive per ton of o re .

Underground Mining

Mining underground was by room-and-pillar mining method, and t h e d r i l l i n g was done wi th jackleg mounted d r i l l machines. Compressed a i r f o r d r i l l i n g was suppl ied by t h e 600-c.f.m. and t h e two 315-c.f .m. r o t a r y compressors. The d r i l l s used 6-foot , 7/8-inch hexagonal hollow d r i l l s t e e l with clhisel type I- 17132-inch carbide- i n s e r t b i t . Each d r i l l round cons i s t ed of e ighteen 5-1/2- foo t holes , and was b l a s t e d wi th semigela t in dynamite. An average of 0.8 pound of explosive was used t o break one ton of o re . D r i l l i n g aind b l a s t i n g t h e o r e cos t $3.80 per ton.

P rope r t i e s of t h e explosives a r e shown on Table 1.

TABLE 1. - Explosives c h a r a c t e r i s t i c s and loading data1

Explosives Data: Type of explosive............. S t i c k count. .per 50-pound case Weight s t r eng th . . ..... .percent Density. .pounds per cubic f e e t Rate of detonat ion. . . . . . . . feet

per second Car t r idge diameter ....... . inch Car t rd ige length .......... inch Type of package.. ........... .. Water res i s tance . . . . . . . . . . . . . . Type of ini t ia t ion. . . . . . . . . . . .

Loading Data: Explosives pe r foot of h o l e . . , . . . .p ounds pe r f e e t

Explosives per .... ho le . . .pounds per ho le T o t a l explolsives--

round.. . .pounds per 6 f e e t Kind o f s t €arming ........... Point of detonat ion. . . . . . . .

Type of delays ............. ..... I n t e r v a l of delays. . . .

Overburden

Quarry dynamite Four 12-1/2-lb. bags 30 59

f r e e running poor primer3

Semigelat in dynamite. 130. 40 . (2)

11,500. 1- 1/4. 8 . wax paper. good. primer. 3

Open-pit o r e Underground o r e

Ore -

- 68.8

d r i l l c u t t i n g s none bottom 2nd s t i c k from

bottom. mi l l i second fuse timing mi l l i second 1 inch of fuse

i n t e r v a l

Surface was t e

- d r i l l c u t t i n g s .

bottom, mil l isecond. mil l isecond

i n t e r v a l . - ' s t r eng th andl r a t e of de tonat ion from manufacturer 's s p e c i f i c a t i o n s . 2 ~ e n s i t y of s t t i ck dynamite i s expressed i n terms of t h e number ( i n t h i s case

130) of 1-1/4 x 8 c a r t r i d g e s contained i n a 50-pound case. 3 ~ r i m e r consi.sts of e l e c t r i c b l a s t i n g cap i n s e r t e d i n a 1- 1 /4 x &inch dynamite

c a r t r i d g e .

Loading and Transportat ion

For rernc~ving overburden, t he company rented diesel-powered shovels of two d i f f e r e n t sin:es. A t t h e s t a r t of t h e opera t ion a 3/4-cubic-yard shovel was f i n t e d a t c o s t of $18.50 per hour, which included wages of t h e opera tor and t h e o i l e r . I a t e r , when t h e r o t a r y d r i l l was i n use i n t h e open-pit operat ion, a 1- 1/2- cubic: yard shovel was r en ted a t a c o s t of $25 -00 pe r hour; t h i s p r i c e a l s o included the wages of opera tor and o i l e r . I n t h e e a r l y s t ages of t he open- p i t operat ion, ,the overburden was hauled by end- dump 15- ton- capaci ty t rucks . The average haulage d i s t ance was 800 f e e t . Af t e r t h e p i t was devel- oped, waste was dumped i n t h e cen te r of t h e mined a rea . This reduced t h e haulage d i s t ance from 800 t o about 300 f e e t .

A bul ldozer was used i n the pit to maintain the haul road and loading a r e a and t o he lp move t h e overburden t o t h e waste dump.

A front-end loader w a s used t o load the o r e i n t o t rucks ; average c o s t of loading o r e w a s $0.55 per ton. The contracted cos t of t rucking ore from the p i t t o the company's m i l l (48 mi les) w a s $3.47 per long wet ton.

I n the underground opera t ion the o re was removed by double-drum s lushe r h o i s t s . The ore was slushed ou t from underground t o a poin t j u s t beyond the p o r t a l of the d r i f t , then loaded i n t o 16-ton end-dump s e m i t r a i l e r s by the front-end loader .

Production

The average r a t e of o re production from the open p i t , 300 tons per day from 1956 t o 1958, required removing 1,200 tons of overburden d a i l y . S t r i p - ping was conducted 1-1/2 s h i f t s per day, and o r e was mined 1 s h i f t per day, 6 days per week.

The production during the f i n a l year of opera t ion (1959) was 150 tons per day, a l l from underground mining. The underground mine was operated 2 s h i f t s per day, 6 days per week.

Table 2 g ives the annual production and grade of o re .

TABLE 2. - Black Rock mine production d a t a (long dry tons)

Year

Mine Organization

1959... Tota l

Personnel a t the mine included the super in tendent , who was i n complete charge of the opera t ion; a genera l mine foreman respons ib le f o r d r i l l i n g , b l a s t i n g , shovel and t ruck opera t ions , and ore shipping; a mechanic, i n charge of maintenance of equipment and f a c i l i t i e s ; and a mining geo log i s t , respon- s i b l e f o r a l l engineering.

M i l l o r e Tons 1 percent

The open-pit opera t ion was concluded before mining underground began. The average mining crew employed f o r each opera t ion i s shown on Table 3.

23,593

No bonuses were paid. Wage r a t e s i n e f f e c t a t the Black Rock mine i n 1958 a r e shown on Table 4 .

Sin te r ing o re Tons 1 Percent

-

Tota l - Tons I Percent

157,604 19.71 962 39.12 158.566 19.82 25.62 536 40.20 24,129 25.94

TABLE 3 . - Average mine crew

TABLE 4 . - Wage Rates i n 1958

Job c l a s s i f i c a t i o n Machine d r i l l e r :

Wagon d r i l l . . . . .... Jackleg.. ..........

D r i l l he lper . . ....... Bulldozer opera tor . . . Labor..... . . ..........

Total . . .........

Hourly wages Job c l a s s i f i c a t i o n :

Bulldozer opera tor . . . . . . . . . . $3.00 Mechanic .................... 2.46 Machine d r i l l e r . . . . . . . . . . . . . 2.25 Scraper operator . . . . . ....... 2-05 Laborers..... . . . . . . . . . . . . . . . 1.80

Open p i t

6 - 3 1 2

12

Mine Surface P lan t

Underground

- 6 3 1 2

12

The su r face p l a n t cons is ted of a mine o f f i c e , shop, compressor house, and fuel- s to rage bui ld ing . A l l were frame cons t ruc t ion covered wi th corrugated shee t metal . Most of t h e minor r e p a i r s on equipment were made a t the p i t , equipment needling major r e p a i r s was sen t t o the main shop a t t h e m i l l . Fuel o i l , l u b r i c a t i n g o i l , and grease were s t o r e d i n a sepa ra t e bui ld ing .

Compressed a i r fo r d r i l l i n g w a s suppl ied by one 600-c.f.m. and two 315- c.f.m. r o t a r y compressors. Major mine equipment used a t t h e Black Rock mine i s shown on ta.ble 5.

Water f o r t h e mine p r o j e c t was piped from a windmill w e l l about 112 mi le from t h e mine. No bunkhouse f a c i l i t i e s were a v a i l a b l e a t t h e mine, and t h e r e was no change room. The workmen commuted from Aguila, Ar iz .

Safe ty P r a c t i c e

The mine foreman, i n add i t ion t o h i s r egu la r du t i e s , ac t ed a s s a f e t y engineer and h.eld monthly s a f e t y meetings wi th t h e crew. Safe ty top ic s were discussed, and. t h e employees were requested t o br ing unsafe p r a c t i c e s and con- d i t i o n s t o the. a t t e n t i o n of t h e management.

The explosives magazine was 1 /2 mi le no r th of t h e p i t . It had a wooden f loo r , was v e n t i l a t e d , and was kept locked a t a l l times. The b l a s t i n g cap magazine was a. wooden- f loored 6- by 6- foo t £ram bui ld ing; i t was v e n t i l a t e d and was kept 1.ocked. Danger s igns were displayed prominently a t both magazines .

TABLE 5. - Inventory of major mininp equipment

Type o f equipment Compressor. ............

DO. . . . . . . . . . . . . . . . . . . Wagon-mounted d r i l l . . . . T rac to r , w i th f ron t - end

loader ..............., Bul ldozer . . . . .,......., A i r - leg- type rock d r i l l S lusher (double drum) . .

DO^^^^^^^^^^^^^^^^^^^

Truck, end dump.. ...... Truck, s e m i t r a i l e r end 1

Q u a n t i t y 1 2 4

1 1 5 4 1

Generator ( l i g h t p l a n t ) . Power shovel . . . . . . . . . .

D ~ ~ ~ ~ ~ o o . . ~ . o . . ~ . . ~ ~ ~

Rotary d r i l l . . .........

1 1 1 1

40 hp ........... 191 hp.. ........ 2- 5/8- i n . . ...... 42- i n . s c r a p e r . . 36-in. s c r ape r . .

S i z e o r c a p a c i t y 600 c.f.m...... .

30-in. s c r ape r . .

--

Rlemar ks D i e s e l powlered.

3 kv.-a ......... 3 / 4 cu. yd ...... 1-1/2 cu. yd.. .. 3- 1/2- i n . ho le , ....... 1,000 f t 15- ton . . ........

Do. Pneumatic.

D i e s e l powered. Do

Pneumatic. Rope speed 132 £.p.m. Pneumatic. Rope speed

160 £.p.m. Pneumatic. Rope speed

121 £.p.m. Gasoline powered, D i e s e l powered,

Do.

Gasoline powered. D ie se l powered.

........ dump. ................. I 6 1 16- ton. . I Gasoline powered.

The mine o f f i c e se rved as a f i r s t - a i d room and w a s equipped wi th f i r s t a i d supp l i e s . F i r s t - a i d t r a i n i n g was given t o employees by Federa l Bureau of Mines s a f e t y engineers .

Sa fe ty r egu la t i ons , such a s wearing hard h a t s , s a f e t y goggles, r e s p i r a - t o r s , and hard- toe shoes, were enforced. Sa fe ty b u l l e t i n s and p o s t e r s ob ta ined from t h e Nat iona l Sa fe ty Council, and t h e S t a t e I n d u s t ~ r i a l Commission were d i sp layed on b u l l e t i n boards.

CONCENTRATING

The company opera ted a concen t r a t i ng p l a n t about 4 mi les f~tom Wickenburg a long the Hassayampa River . The o r e was concent ra ted by g r a v i t y s epa ra t i on , f l o t a t i o n , o r a combination of t h e two methods.

Ore was hauled 48 mi les from mine t o m i l l i n s e m i t r a i l e r s . The cable- opera ted end-dump s e m i t r a i l e r s hauled an average of 16 tons pe r load. Custom o r e was rece ived a t t h e m i l l 24 hours a day, 7 days a week. Adequate coa r se and f i n e b i n capac i ty was provided f o r each type of o r e be ing r ece ived .

Organizat ion

The m i l l crew by s h i f t s i s shown on t a b l e 6 .

I n add i t i on , an average of 10 l abo re r s were used f o r u n c l a s s i f i e d and miscel laneous work, making a t o t a l of 39 men employed i n operati .ng t h e m i l l . Labor d i s t r i b u t i o n i s shown i n t a b l e 7.

TABLE 8. - M i l l power d i s t r i b u t i o n

Item: Crushing..... . .... Fine grinding. . . . . F lo ta t ion . . ....... Heavy media ....... Tables . . ,mm. . . . . . .

Percent of t o t a l 10.0

Item: Water supply ...... Assaying .......... Yard work.....m...

Tota l . .........

Percent of t o t a l - 5.5

DEEP WELL ( PUMP NO. I )

DOMESTIC TANK ( LA80RATORY9 SHOP, CHANGE ROOM 1

* 33,400 GAL. MILL STORAGE TANK

h

t t 7 PUMP NO, 2 PUMP NO. 3 PUMP 1\10. 4 PUMP NO. 5

GRINDING SECTION HEAVY ME:DIA SECTION

FLOTATION SECTION TABLE SECTION (FIG. 9 ) (FIG.8)

FIGURE 6. - Diagram of Water Distr ibut ion.

t

PUMP NO. I

2

3

4

5

TYPE SIZE DEEP WELL 4 0

CENTRIFUGAL 15

DO 10

DO 3" 15

DO 7- lh

Ore Treatment

rzaw Flowsheets of t h e var ious operat ions a r e shown on f igures 7, 8, and 9; major items of equipment a r e numbered t o correspond with more d e t a i l e d desc r ip t ions on Table 9. An a e r i a l photo of t h e m i l l a r e a i s shown on f i g u r e 10.

TABLE 9. - Inventory of milling, equipment

,-- Unit No.

1

.".a-

2 3 4 5 - 6 7 8 9

10 11 12 13 14 15 16 1 7 18 19 20 21 22 23 24 25 26 27 28

Descript ion

Truck s~~ale . . . . . . . . . . . . . . . . . . .... .................... Ore s t o c k p i l e .......... Bin, coarse-ore s to rage ............ Feeder, r ec ip roca t ing Crusher, impact. ................. Conveyor, belt...................

DO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....... Screen, 1/2" double deck.. Conveyor, bel t . . . . . . . . . . . . ....... Sampler .......................... ........... Bin, finle-ore s torage . Ore s t o c k p i l e .................... ...... Ore bin, f ine-ore s torage . . Conveyor, be l t . . . . . . . ............

............ Bin, f ine-ore s to rage Conveyor, b e l t . .................. ............ Bin, f ine-ore s to rage Conveyor,, belt . . . . . . . . . . . . . . ..... ......... Magnet, :suspended type.. . .....* Crusher, shor thead cone. :. Conveyor,, b e l t . . ............. .... Feeder, v i b r a t i n g ................ Conveyor, belt................... Scale, conveyor.................. ...... Screen, 3/16" double deck.. ................. Cone separa tor . . Screen, low head drainage and washing,, 10 mesh.. ..............

Pump., salnd......... .............. Magnetic separa tor , be l t . . . . , . ... Pump, salnd....................... DensifFe:r, s p i r a l . ............... ............. Demagnetizing c o i l . . ........... Pump, v e r t i c a l , sand.. Conveyor, belt . . . . . . . . . . . . . . . . . . . Bin: storage,. . . . . . . . . . . . . . . . . . . . Conveyorl b e l t . ......,........... Pump, sand....... . . . . . . . . . . . . . . . . Cyclone c l a s s i f i e r . . . . . . . . . . . .*..

Required No. 1

Capacity o r s i z e

40 ton. . ........ ................ 50 ton.. . . . . . . . . 2 'x6 ' . .......... 30'1~3011. ........ 36I1x13 I 6". ...... 24"x38 ' ......... 18"x124'.... .... 16". ............ 110 ton ea. . . . . . ................ 15 ton.. . . . . . . . .

18"x108 '........ 110 ton. . . . . . . . . 18"x25 '......... 90 ton.. . . . . . . . . 18"x43 .......... 1211~161' ......... 24'' ............. 18"x45 . . m a . . . . . . ................ 18"x140 '........ 2400 ton.. . . . . . . 3 'xlZ '.......... 7 ' ..............

Tota l h i .

TABLE 9 . . Inventory of m i l l i n g equipment (con.)

Un i t No . -

40 41 42 43 44 45 46 47 48 49 50 51 52 53

54 55 56 57 58 59 6 0 6 1 62 63 64 65 66 6 7 6 8 69 70 7 1 7 2 7 3 74 75 76 77 78 7 9 80 8 1 82 83 84 85

Desc r ip t i on

D i s t r i b u t o r . r evo lv ing ........... Table. concen t r a t i ng ............. Pump. sand .......................

DO ............................. C l a s s i f i e r . dewater ing ........... Screen. 20 mesh ............... ,.. Thickener .........O..............

.................. Conveyor, screw DO .............................

C l a s s i f i e r , dewater ing ........... Pump, diaphragm ...............,,, Tank, mi l l -wate r s t o r a g e ......... Conveyor, screw .................. Concrete s l a b , open s t o r a g e w i th

d i v i d e r s ........................ Compressor, a i r .................. Conveyor, b e l t ...................

DO ............................. .................. Conveyor. screw

DO ............................. Pump, sand .. ..................... .......... C l a s s i f i e r , duplex rake

.................. Conveyor, screw Pump, sand ....................... Thickener .. Pump, diaphragm .................. A g i t a t o r ......................... Pump, sand ....................... Dis t r i bu to r , , ....... .............. ............... 4 - c e l l cond i t i one r ............... 5 - c e l l cond i t i one r .................. 12- c e l l rougher 6 - c e l l rougher ................... Pulp sampler ..................... Pump, sand ....................... Pulp sampler ..................... Pump, sand ....................... ............. . 3 - c e l l No 1 c l eane r

DO ............................. 3 - c e l l No . 2 c l e a n e r ............. 3 - c e l l scavenger ................. Pump. and...............^....... ............. 3 - c e l l No . 2 c l e a n e r Pump. v e r t i c a l . sand ............. Pump, sand .......................

Required No . 1 8

2 1 1 1 1 1 1 1 1 1 1 2 1 2 1 1 2

1 bank 1 bank 1 bank 3 banks

1 1 1 1

1 bank 1 bank 1 bank 1 bank

1 1 bank

1 1

Capac i ty o r s i z e To ta l hp .

TABLE 9. - Inventory of m i l l i n p equipment (Con.)

u n i t I Descr ip t ion 1 Required 1 Capacity o r s i z e 1 Tota l hp. No. -

86 8 7 88 89 90 91 92 93 94 95 96 97 98 99

100

Pump, sand.. . . . . . . . . . . . . . . . . . . . . . Pump, v e r t i c a l , sand.. ........... Thickener..... . . . . . . . . . . . ........ Pump, df~aphragm.. ................ ........... F i l t e r , American type. Concrete s lab , s torage. . . . . . . . . . . Pump, c tmt r i fuga l ................ Tank, reagent mixing. ............ Tank, reagent , s torage. . . . . . . . . . . Pump, c e n t r i f u g a l . ............... D i s t r i b u t o r ...................... ....... Pump, reagent d i s t r i b u t i o n Tank, a c i d s torage. . . . . . . . . . . . . . . Feeder, vibraflow... . . . . . . . . . . . . . Tank, Polyacry lamide f l o c u l a n t mixing .......................... ........... Tank, sitorage..... . . . .

Conveyo~r, be l t . . . . . .............. Pump, vacuum...... . . . . . . . . . . . . . . .

1

Phys ica l c h a r a c t e r i s t i c s of manganese minerals i n t h e o r e determined t h e m i l l i n g procedure. For example, a f t e r crushing ores conta in ing l a r g e high- grade nodules of manganese oxide, p l u s 3/16-inch p a r t i c l e s were t r e a t e d by heavy media concentrat ion. Minus 3/16-inch m a t e r i a l was concentrated by wet t a b l i n g wi th ,slime f r a c t i o n t r e a t e d by f l o t a t i o n . Crude o res conta in ing man- ganese in t ima te ly a s soc ia t ed with t h e gangue a l s o were t r e a t e d by f l o t a t i o n a f t e r being ground t o l i b e r a t e manganese p a r t i c l e s .

Capacity of t h e m i l l depended upon grade of crude o re . Under optimum condi t ions , m(aximum capaci ty was 750 tons per 24 hours . The crushing p l a n t normally oper'ated 16 hours per day, 7 days per week; t h e concent ra tor r a n 24 hours per day, 7 days per week.

Primary crushing was t o 1-1/2-inch s i z e and was performed by a 30- by 30-inch impact crusher , proving e f f e c t i v e f o r a l l kinds of manganese ores . Crushed o r e was conveyed t o a double-deck 4- by & f o o t 112-inch screen. The over s i ze was conveyed p a s t a suspended-type magnet t o remove any tramp i ron . It then was crushed t o minus 1/2- inch i n a short-head cone crusher i n c losed c i r c u i t with t h e screen. The undersize product was conveyed t o t h e f ine-ore b in . Dust l o s s was con t ro l l ed by water sprays a t a l l t r a n s f e r po in t s .

The crushed and screened product was sampled by an automatic sampler, producing a f i n a l sample of one pound per ton of crushed ore . The crushed o r e was discharged onto conveyors and t ranspor ted t o d i f f e r e n t s to rage b ins , depending upon t h e m i l l c i r c u i t requi red .

CRUSHING SECTION

TRUCK SCALE a,,----- - - --I I I I I

16" GRIZZLY I ORE STOCKPILE @ I

ORE BIN @ o I + :I FEEDER @ ?I

ORE BIN @ 1 3

I CRUSHER @ I

4 I CONVEYOR @ I

CONVEYOR @ I 1

I

+ I + 1/2"

I 1

CONVEYOR @ + SAMPLER @

OPTIONAL r---------

I I 3 ORE BINS @ I I I

I I I I I I I I I +

CONVEYOR @

2 ORE BlNS @

t

I coNV:YoR @ I

I I (OPTIONIIL)~ - - - - - 1 ' MAGNET @

CONE CRUSHER @)

1 CONVEYOR @

TO GRAVITY SECTION

TO FLOTATION SECTION 0 SEE TABLE 9

FIGURE 7. - F lowsheet o f Crushing Section.

GRAVITY SECTION

FIGURE 8. - Flowsheet of Gravity Section.

maw"

FIGURE 10. - Aerial Photo of the M i l l Area. (1) Pr imary ore crusher, (2) Secondary cone crusher, (3) Water storage tank, (4) Heavy media plant, (5) Tables, (6) Crushed ore bins, (7) Bal lmi l ls , (8) Thickeners and fi l ter, (9) F lo tat ion section, and (10) Reagent section.

( C o u r t e s y o f Mohaue Mining and Mi2ling Co.)

From t h e b ins supplying t h e g r a v i t y s e c t i o n of t h e m i l l , v i b r a t i n g feeders moved t h e o r e t o a conveyor b e l t t h a t discharged onto a 3- by 12-foot double-deck 3/16-inch screen. The ove r s i ze m a t e r i a l from t h e screen was t r e a t e d i n a heavy-media sepa ra to r us ing minus 65-mesh f e r r o s i l i c o n . Con- sumption of f e r r o s i l i c o n was from 0.25 t o 0.50 pounds pe r ton of o r e t r e a t e d . Concentrate from t h e heavy media p l a n t was t rucked t o t h e r a i l r o a d and s o l d as type I1 ore . According t o National S tockpi le Spec i f i ca t ion P-30-R, da ted January 8, 1953, type I1 was n a t u r a l ore, unprocessed except f o r grading, washing, o r screening, w i th not more than 15 percent pass ing a ~ ~ l e r ' Stand- a r d Sieve Mesh No. 20 o r U.S. Standard Sieve No. 20,

Undersize from t h e 3/16-inch sc reen w a s s i z e d and dewatered i n cyclones, y i e l d i n g two products-- sand and sl imes. The sand passed t o the concent ra t ing t a b l e s . The concent ra te from t h e t a b l e was s i z e d by a 4- by 7--foot screen producing a p lus 20-mesh f r a c t i o n t h a t was shipped t o General Services Admin- i s t r a t i o n (GSA) a s type I1 ore . Undersize from t h e screen (minus 20-mesh) was t rucked t o the s i n t e r i n g p l a n t f o r f u r t h e r processing. Table ka i l i ngs were e i t h e r discarded o r were t r e a t e d by f l o t a t i o n t o recover a l l a v a i l a b l e manga- nese. They were r e c l a s s i f i e d before f loa t ing , t h e s l imes being thickened, and t h e sand f r a c t i o n was ground f o r l i b e r a t i o n of manganese. The s l imes (minus 250-mesh) from t h e cyclones ahead of t h e t a b l e s were passed through t h e same thickener as t h e t a b l e t a i l i n g s l imes be fo re going t o t h e f l o t a t i o n c i r c u i t f o r t reatment . Both s l imes were thickened t o 29- t o 31-percent s o l i d s fo r f l o t a t i o n .

Capacity of t h e f l o t a t i o n p l a n t t r e a t i n g t h e combined sand and sl imes was approximately 12 tons per hour. Feed t o t h e f l o t a t i o n c i r c u i t s averaged 18 percent manganese. F l o t a t i o n r ecove r i e s ranged from 86 t o 92 percent , and concent ra tes averaging 44 percent manganese were produced.

I n t h e f l o t a t i o n s e c t i o n t h e primary gr inding was accomplfished by two b a l l m i l l s , 6- by 5- f e e t and 5- by 10- f e e t , ope ra t ing i n c losed c i r c u i t wi th one 8- by 24-foot duplex r ake c l a s s i f i e r . Crude o r e and t h e sand f r a c t i o n from t a b l e t a i l i n g s were ground, were c l a s s i f i e d t o minus 65-mesh, and were pumped t o a thickener . The thickened sl imes from t h e g r a v i t y s e c t i o n and t h e minus 65-mesh pulp were pumped t o an a g i t a t o r , then combined pulp was t r e a t e d by f l o t a t i o n .

The concent ra tes were cleaned a s many a s t h r e e times, depending upon t h e s i l i c a and alumina content . They then were pumped t o t h e thickener , were f i l t e r e d , and were t rucked t o t h e s i n t e r i n g p l a n t t o be nodulized fo r shipment.

The s i n t e r i n g p l a n t was about 7 mi les no r th of Wickenburg along the Atchison, Topeka and Santa Fe Rai l road i n YavapaF County. Fine concent ra tes from t h e m i l l and s i z e d crude custom o r e s were s i n t e r e d i n a st:andard commer- c i a l m a c h i n e having a moving grade and a capac i ty of 150 tons pe r day. The

' ~ e f e r e n c e t o s p e c i f i c brand names o r makes and models of equipment i s done t o f a c i l i t a t e understanding and does n o t imply endorsement of such items by t h e Bureau of Mines.

machine w a s designed p r imar i ly t o r o a s t m e t a l l i c s u l f i d e s before smelt ing i n t h e b l a s t furnace but was adapted t o agglomerate f i n e p a r t i c l e s ( s in t e r ing ) of nonsul f ides by adding c o a l o r coke t o t h e charge. A s t h e f u e l i n t h e charge i s burned, enough h e a t i s given o f f t o fuse t h e f i n e p a r t i c l e s i n t o l a r g e r coherent masses ,,

The charge i s mixed, moistened, and then spread i n a uniform l aye r on a s e r i e s of moving p a l l e t s t h a t have gra ted bottoms. A s t h e p a l l e t s move through t h e machine, t h e charge passes over a suc t ion windbox and, a t t h e same time, t h e f u e l i n the charge i s i g n i t e d by a burner . The burner i s over t h e charge and i n l i n e with the windbox. The amount of s i n t e r i n g may be con- t r o l l e d by vary ing t h e r a t e of t r a v e l o f t h e p a l l e t s , t h e amount of f u e l i n t h e charge, o r t h e v e l o c i t y of t h e a i r b l a s t through t h e charge.

Concentrates from va r ious sec t ions of t h e m i l l , conta in ing d i f f e r e n t amounts of contaminates, were blended t o produce a f i n a l product from t h e s i n t e r i n g p l an t , conforming t o s p e c i f i c a t i o n s f o r type I11 manganese. Accord- i n g t o spec i f i ca t ion , type 111 nodules o r s i n t e r c o n s t i t u t e m a t e r i a l which has been agglomerated by the a p p l i c a t i o n of hea t below the po in t of fusion, with n o t more than 5 percent by weight pass ing a Tyler Standard Sieve Mesh No. 20 o r U.S. Standard Sieve No. 20.

Before s i n t e r i n g , blended concent ra tes were thoroughly mixed with petro- leum coke; windrowing was done wi th a motor grader . Petroleum coke i n t h e mixture was approximately 5 percent of t h e weight of manganese concentrate . This mixture was loaded i n t rucks by a front-end loader and was t ranspor ted t o the s i n t e r i n g b ins . It was conveyed t o t h e pugmill where water was added t o ob ta in a moisture content of 4.5 percent ; then i t was passed through a rotat ing-pel let iz ing-drum, and t h e r e s u l t i n g p e l l e t s conveyed t o the s i n t e r i n g hea r th ( f i g . 11). An a e r i a l photo of t h e s i n t e r i n g p l an t a r e a i s shown on f i g u r e 12.

Bedding m a t e r i a l (crude o r e crushed and s i z e d a t t h e s i n t e r i n g p l an t ) was f i r s t l a i d down on t h e p a l l e t s t o a th ickness of 1 / 2 inch. This was topped wi th 4 t o 6 inches of t h e petroleum-coke-mixed concent ra te . This layered mix- t u r e was d i s t r i b u t e d evenly across t h e f u l l width of t h e p a l l e t . As the pal- l e t moved from the feed hopper t h e charge passed under a butane i g n i t e r a t t h e head of t h e wind box, The i g n i t e r p ro jec t ed on i n t e n s e flame across a narrow t r ansve r se s t r i p of t h e upper su r face of t h e bed, k i n d l i n g t h e f u e l i n t h e mixture. The mixture continued over t h e suc t ion box where s i n t e r i n g took p lace . With proper con t ro l of s i n t e r i n g , enough lead and z inc were v o l a t i l i z e d so t h a t t h e agglomerated product d id no t exceed s p e c i f i c a t i o n l i m i t s f o r these base meta ls . The s i n t e r e d m a t e r i a l was then fed i n t o a s i n t e r breaker and crushed s i n t e r dropped on a double-deck 20-inch by 20-foot n a t u r a l frequency screen . P lus 10-mesh m a t e r i a l was conveyed t o s to rage p i l e s f o r shipment i n r a i l r o a d c a r s a s type I11 manganese, and minux 10-mesh m a t e r i a l was re turned t o the s i n t e r i n g p l a n t b i n s fo r reprocess ing .

Power for t h e s i n t e r i n g p l a n t w a s obtained from Arizona Publ ic Service Co., Wickenburg, Ariz. , t ransmi t ted a t 12,000 vo l t s and transformed t o 440 v o l t s by t h r e e 75-kv.-a. t ransformers on t h e proper ty .

SlNTERlNG PLANT CAPACITY 150 TONS PER DAY

MlLL CONCENTRATES ~RMIXED WITH COKE

2 BINS 12~x8' I

1 2 BELT FEEDERS

/-,,.I 1 SCREENS

CUSTOM ORES I

1 BELT CONVEYOR

BUCKET ELEVATOR 50'

1 4 BIN 5 ' ~ 4 '

WATER BEDDING MATERIAL

I BIN 6 ' ~ 5 ' CRUDE ORE +1/4"-1/2"

I I

CRUSHER I

+ BELT FEEDER 24"

I SINGLE-ROTOR PUG MlLL 18' '~8 '

ROTARY PELLETIZER 3 0 ~ ~ x 5 '

4 I v

DWIGHT LLOYD SlNTERlNG MACHINE 4 2 " ~ 264''

SINTER BREAKER

CONVEYOR 24" t 1 + 1 °

- 10 MESH

I!?€INING AND MILLING COSTS

The l i f e of t h e opera t ion w a s est imated t o be r e l a t i v e l y s h o r t ; therefore , t o avoitl a high amor- t i z a t i o n r a t e heavy equipment was rented, or t h e work was con- t r a c t e d . The con- t r a c t r a t e f o r dri1:Ling 4- 1/2- inch b l a s tho le s , averaging 54 f e e t deep , was $1.25 pe r foo t .

One shovel, e i t h e r 3/4- o r l- 1/2- yard capac- i t y , was requi red . Renta l r a t e fo r t h e small shovel was $18.50 per hour and f o r t h e l a r g e shovel, $25.00, inc luding wages of opera tor and o i l e r i n both cases . Each of t h r e e 15- yard end- dump t rucks were r en ted a t $10.50 per hour, includ- i n g wages of d r i v e r . Ore was hauled 48 miles from mine t o m i l l by c o n t r a c t ; t h e r a t e was $3.47 per long wet ton.

TYPE m ORE TO RAILROAD

FIGURE 11. - Flowsheet of Sintering Plant.

Table 10 shows d i r e c t min- ing c o s t s of t h e open-pit opera t ion f o r a 3-month

FIGURE 12. - Aer ia l Photo of Sintering P lan t Area. (1) Warehouse, (2) Petroleum coke storage, (3) Sinter ing plant, (4) Crushing plant, (5) Sintered material storage, (6) Concentrate storage, (7) Mix ing windrows, (8) Bedding mater ial storage piles, and (9) Maintenance shop.

(Cour te sy of Mohave Mining and MiZZing Co.)

per iod i n 1958, when t h e mine was opera t ing on one s h i f t a day f o r 25 days a month and w a s producing an average of 300 tons of o r e a day. Proper ty tax, i n t e r e s t , deprec ia t ion , and dep le t ion a r e not included.

TABLE 10. - Sunnnary of open-pi t mining c o s t s (Cost pe r ton of o r e mined)

Item Operating

labor

Str ipping. . . ...........m...... D r i l l i n g and b l a s t i n g ......... Loading trucks.. . . . . . . . .......

Costs of labor , power, and supp l i e s f o r concent ra t ing 6,218 tons of o r e i n January 1959 by heavy media, t ab le s , and f l o t a t i o n a r e summarized i n t a b l e 11.

Power, maintenance,

Engineer s e r v i c e s . . . . . . . . ~ . . .. Haulage t o m i l l (48 mi les) . ....

Tota~. . . . . . . . . . . . . . . . . . ..

TABLE 11. - D i s t r i b u t i o n of m i l l i n g c o s t s , percenr

T o t a l

$1.56 . 75 -52

I t e m

and supp l i e s $0.25 $1.81

-20 .03 -

- -

Crushing. .......... .... Fine gr inding .......... Flotat ion. . . . . . . . . . . . . . Heavy media............ Tables..... . . . . . . . ..... Yard work..... . . . . . . . . . Assaying. ............., .......... Water supply.

- - - 6.82

Total.... . . . . . . . . . Supervision ........,...

Grand total,^^....

The company mi l l ed crude o r e from approximately 225 d i f f e r e n t producers, These var ious types of o r e n e c e s s i t a t e d d i f f e r e n t t reatment methods o r corn b i n a t i o n procedures, depending upon t h e grade and t h e phys ica l c h a r a c t e r i s t i c s of t h e manganese o res . The f l o t a t i o n cos t f i g u r e was high because t h e reagent c o s t was about $4.60 pe r ton of ore . Average c o s t fo r custom-milling proc- e s s i n g i s shown on t a b l e 12.

Labor Operating

3.2 3.9 9 .5 3.2 3 .3 1.2 1.6

T o t a l

7 .l 11.4 48.7

7.1 6.2

10.5 2 - 3

Maintenance 0.7 3.0 1.7 1.1 . 7 1.8 -

Power and supp l i e s Operating IMaintenance

2.5 3.7

36 .O 2.2 . 7 3.2 . 7

0.7 .8 "

1.5 .6

1.5 4.3 -

TABLE 12. - Average process ing c o s t s

Heavy media... $0.91 per ton of crude o r e t r e a t e d . Tables. . , . . . . . 31 D o . F lo ta t ion . . . . . 6.80 Do . Sinter ing . . . . . 5.52 per ton of concent ra te t r e a t e d .

One o the r major 'opera tor i n Arizona repor ted production c o s t s i n round f igu res , per ton of o r e mined, a s follows : Open-pit mining, $2.00; under- ground mining, $11.00; m i l l i n g ( j i g s , heavy media, and t ab le s ) , $3.80; and t r anspor t a t ion , $1.50; t o t a l i n g $7.30 a ton f o r open-pi t ore, and $16 -30 a ton f o r underground ore. A New Mexico opera tor quoted a round f igu re cos t of $35.00 a ton fo r underground mining, t r anspor t a t ion , and j i g mil l ing-- concent ra te de l ive red t o r a i l r o a d s id ing .