Information Circular 6113: Method and Cost of Mining Zinc and Lead at No. 1 Mine, Tri-State Zinc and Lead District, Picher, Oklahoma
Information Circular 6113: Method and Cost of Mining Zinc and Lead at No. 1 Mine, Tri-State Zinc and Lead District, Picher, Oklahoma by United States…
Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.
i MAY 14 29
CircuLar No. 6113. ApriL, 1929.
Information Circular
Department Of Commerce Bureau Of Mines
METHOD AND COST OF MINING ZINC AND LEAD AT NO. 1 MINE, TRI-STATE ZINC AND LEAD DISTRICT, PICHER, OKLAHOMA.
BY Wwe. F. NETZEBAND
Washington, D. C., April, 1929.
This paper is the second of a series of publications dealing with mining methods and costs in the metal mines of the United States. The first paper, which discussed the Method and Costs of Mining Magnetite in the Mineville District, New York, was published as Information Cir- cular 6092, and, like the present paper, dealt with an operation employ— ing open stopes with pillar support.
Reports on 18 additional mines using the open stope method are in the course of preparation. After these reports are completed and published separately in Information Circular form, it is proposed to issue a bulletin in which will be discussed the open stope method with its variations, its application and limitations, and the costs of mining under the various conditions where it is employed.
Reports on other methods of mining are also being prepared, and it is planned to deal with these methods in a Similar manner.
These papers are all being written by officials and engineers of mining companies in accordance with an outline prepared by the Bureau of Mines
for the purpose of obtaining uniform and comparable data.
howvtz—cL eumen SCOTT TURNER, Director.
Circular No. 6113, April, 1929,
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“DEPART oF commence. BUREAU? oF. ures: #4 a Resale Rake
METHOD AND COST OF MINING ZINC AND LEAD AT.NO. 1 MINE, 0° - TRI-STATE ZINC AND LEAD DISTRICT Be
By Wy, r. Netacband®
“Introduction
. “The purpose of this. paper. is ie ae oe ac operators in other districts a,’ ‘detailed description of the mining method. used and the results obtained in ex- ploiting one of the zinc-lead deposits.of .the Kansas-Oklahoma-Missouri district, No, 1 mine is located in the heart of the town. of Picher’. in the extreme northeast corner of nen
" History:
The first prospect artiitiig WAS - dite at Ws. ¥ ine ‘Late - in: 1914, and. shaft sinking was started early in°1915; Sufficient “dré “was "developed to start construc- tion of the mill in April, 1916. Production began in Angust, 1916, ‘and the mine. has been producing, except.for short periods, to the present time. The property was originally a 40-acre tract; but additional properties: have ‘been consolidated with the original one until the mine now covers ie acres,
- The mill. has a x capacity of 1, ,400 tons’ in ve hours ak is one of. the largest mills in the district, This mill was one of the first'in the district to use flo- tation, a flotation plant having been added'td the mill in the fall ak 1917. :
Piast The surface rock 3 are of Pennsylvanian age," and’ are made up entirely of. shales and sandstones of. the’ Cherokee: formation,’ the thickness: of ‘the Cherokse- in the vicinity of No. ae ming ‘ranges from 60° to 100 se ayy: oe
‘The Cherokee formation lies iine’dnf ormably’ upon “the. oe er and de stones of the Chester formation, the youngest member of: :Mi's sissippian age. This formation, which is entirely absent in many places, has a maximum thickness of 40 feet. In churn drill cuttings ‘it is difficult.to distinguish between the lime- stones of this formation: and Lesool nee Boone: rere: upon which it. rests. with a marked unconformity, - Barge o.oo oe ee 3
Ll The Bureau of Mines will welcome reprinting of ‘this article but requests that the following footnote acknowledgment be made: "Printed by permission of the Director, U. S. Bureau of Mines. (Not subject to copyright. )"
2 One of the consulting engineers, U. S. Bureau of Mines,
Inf. Cir... 6113
The Boone formation is sevens with the Warwaw-Keokuk-Burlington serieg of other areas. It is the principal ore-bearing formation and consists of inter-_ bedded limestones and cherts, It is broken up locally into a number of members, the principal ones being the Short Creek -oolite member, a thin but persistent oolitic limestone, and the Grand Falls chert member, a massive chert occurring 70 to 100 feet below the base of the Short Creek ‘oolite. The thickness: of the Boone ranges from 275 to 325 feet.
Ore Deposits:
The ore deposits of No. 1 mine occur in the brecciated and boulder ground 40 feet below the base of the Short Creek oolite,
This horizon is at the 270-foot or main mine lavit There are two minor ore horizons. mined, one at-230 feet, the Short Creek oolite horizon, and the other at 200 feet. The. upper. or 200-foot level.is of the semisheet ground type; the ore occurs: along the bedding planes and is disseminated throughout the blue and gray chert, The ore on the middle, or 230-foot level, is of the brecciated type.
The ore on the main level occurs disseminated in the jasperoid breccia, as massive lenses or patches and as the lining of vugs and cavities. The gangue ‘minerals are jasperiod breccia, chert, calcite, and dolomite, The accompanying
sketches (figs. 1 and. 2) show the mode of. occurrence of the ore in the different — of ene :
Exploration And Estimation Of Ore Reserves
“There are no surface indications of ore in the district. All exploration — work is done with the churn drill and is usually started by drilling several rows © of holes. across the tract from north to south or east to west at intervals of 200 to 400 feet, until a favorable area has been defined and then drilling the holes closer together,
The earlier holes were drilled 5-7/8: inches in diameter, but later the standard size was changed to 6% inches. Logs of all holes ‘are kept, and assays are made of all values above ee cent blende or 1 per.cent galena; values below - this are recorded as "shines." On the 200 acres constituting the No. 1 mine property 128,204 feet of drilling has been done. The drilling is all done on contract at prices ranging from $1.00 no $1.25 a foot papeneIne upon the character of the ground being drilled.
Estimates of ore reserves are based on a careful analysis of the churn drill records. Past experience has shown that an ore-body mills out about 10 per cent better than the estimate. In estimating tonnage, a factor of 12.5 cubic feet per ton. is used for rock in place,
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Inf, Cir, 6113 EARLY MINING METHODS
The early mining methods were similar to the methods typical of the dis- — trict; hand-shoveling into cans set on trucks, . tramning by mule to the shaft, and hatebiee the can of ore to the surface, 3
When the original Yo. 1 mine was consolidated with the first of the other properties, mechanical haulage with cars instead of cans was installed, A skip hoist was installed at the mill shaft and all ore hauled thereto by trolley locomotive.
Mechanical loaders of var ious types have’ been tried, but none have proved successful. Hand-loading has been found to “be iad id ‘economical method.
As to the mining method, ihe open. iaahe eel with pillar support has continued to be used, since no other method has been found that could be employed satisfactori ly - in this type of ore a 3
‘Tevelopment System
No definite jovliocment estem is peor out once the shaft has been sunk to the ore and the mine opened. up to the product ion stage. The churn drilling has defined the mineable areas, and: the. problem nas resolved itself into keeping the pillars in the leaner ore as. much as possible and at the same ae PEOTAOOOE
adequate support to the roof,.
Prospect drifts, known locally as "pull" drifts, are driven nal of the workings as the occasion requires, but these are usually driven to an isolated, previously proved ws with the idea of later using them as ae drifts.
Main Shaft. The main or mill shaft was originally sunk at the wi site on the original tract. The shaft is 5 by 7 feet in cross section, the standard size for shafts in the district, . It-is sunk to the 270-foot level which is the main haulage level for the mine. -Originally. it was equipped with the usual type of Joplin hoist, using cans to bring the ore to the surface, ‘The standard can holds about 1,400 pounds of ore. :
The shaft is close-cribbed witn 2 by 6 inch pine timbers from the collar of the shaft to'a point. below the shale. Careful lagging and. packing behind the cribbing is necessary, since the’ shale. slacks off and gives trouble when wet un- less it is held securely in place so tins .t it can not slum. Below the shale no cribbing is necessary unless loose boul.ier ground is encountered, in which case © "jump" cribbing is tied in above and below to 6 by 6 inch bearing timbers set in hitches in solid rock,
The shaft was equipped for skips in 1920 using 23-ton self—dumping skins and hoisting in pdalance,
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Inf. Cir. 6113
Auxiliary Shafts.- The usual practice in the district is to sink a shaft to an isolated, orebody and tram the ore on the surface, rather than to connect underground and hoist at a central shaft. For this reason the mines usually have two or more "field" shafts for hoisting ore besides the mill shaft.. At No. 1 mine, however, all ore is hoisted at the mill shaft. Before the various properties were consolidated, several shafts were sunk on-each tract, so that at present there are 14 "field" shafts on the 200 acres, The. only one of these in use at present is
equipped with a double-deck cage for handling men and material.
The early shafts were sunk by the company as a regular part of the mining operation, and due to the heavy flow. of water the costs were excessive. The later shafts were sunk on contract, but as all of these were sunk a number of years ago, no costs are available. An average contract price is $12 per foot in shale and $18 — foot in the rocic, the company furnishing everything but labor and pone
Prospect or "Pull" Drifts.- Prospect or "pull" drifts are driven 7 by 7 feet in cross section. The work is. almost..always done on contract, the contractor furnishing all the labor and the company all the equipment. Occasionally a con- tract is let wherein the contractor furnishes sia tac out the track and piping.
The average ‘round with the amounts of powder used is shown in the sketch (fig. 3). The rounds are varied somewhat to meet the changing conditions of the ground, When the ground becomes harder, three or four cut: holes are used, and occasionally it is found necessary to drill ts wO or three extra bottom or — holes in order to assure an even grade, - 7 ,
The powder used. in 1¢ by 8 indies 33 per cent, parrot oe The primers are made up with No..6 caps; the caps are placed in the center of the stick of powder and the entire primer is put. into. safety: id abil for the
Purpo se.
The holes are drilled from a column set in the center of the drift; a, heavy Leyner-type drill is used. All Leyner drills are operated by two men, a runner anda helper. - The cut holes are drilled with 7-foot steels to a depth of 6 feet, and all other holes are drilled with 9-foot steels to a fe of 8 feet. tase rai d 6 feet are broken per round.
The costs given below are based on a adrift which was ponksasion for at the rate of $7.50 per foot, with the contractor furnishing only the labor and the company furnishing everything else.
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Inf, Cir, 6113
Cost per Foot of “Prospect ‘Drift
ee oe a Cost a. Per cent . Pil pe dabot 2 acs see eaadooes ec. $2, 95° 20.8 Mocking Labor .sccccecscsesgerooseactaccce. @042 4 2 Ole. HI LOSIVOS 3604.4 2b4e08, one ae ees stehaveuneaeaie , 2.38 (16.8 Tramming (DOWN): wnapecessaccavecvenersee 611 0G? 6.9 . Labor insurance carried, by contractor . meer —8A4 Compressor Mabe chat acecmeanaemeceueaee © 6 oes a4. Tracking and piping 0.ceeeeeeees 0 46 3.3 a, Ventilation. TO we a Ee Pee re ee cree 043°. 3.0 - Steel. Consumption neicceiedglisasaeteridail - 06 , O4 - Blacksmith. Se a oe (Q-- ; $0.0. Miscellaneous: (carbide, :repairs,.etc..) oo 986" or “Motel, cost per Poot is sew sete. cas yas 13. aie :
When a new orebody is being developed and the rock has to be hoisted to ‘the orale ‘there isan additional: biclade ‘oF 14: cents - foot. — hoisting.
-Ratsess- ‘Raises are: “Hot necessary very: often, when an “isolated orebody is found above the main level'a raise is driven up, usually at an angle of about 459 so that-it can later be used for an ore chute, “The raises are driven 6 by 6 at in cross ives
Wel padead: ‘are drilled froma shaft bar with the same a of heavy Leyner drill that ‘is used in the "pull!" a@rifts, The Yound used is practically. the same as for the "pull" drift, /except that the center stope and roof holes are not used, This cuts down the powder i ll slightly.
‘The contract, ‘price is $3. 50 per foot, but the contractor furnishes only the drilling lahor, The company does the mucking and tramming and supplies all equip- ment, These costs will be practically the same for raises as for "puil" drifts,
After the upper orebody has been developed to assure mining on that level, the raise is converted into an ore chute by putting a front on the lover end with a gate for loading. -If: the-raise is the only means of entrance to the new ore level, a partiion-is built so that part canbe used. for a manway. Usually, -how- ever, two raises are-driven, one to be used for a manway.. This arrangement. always affords better ventilation, and often a raise is driven solely for this purpose. es Forme rly’ all. raises ‘were driven’ vertically with alight stoper, but the inclined raise has been found so’ satisfactory that no vertical raises are now drive:
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Inf, Cir, 6113 PRESENT: MINING METHOD
The plan and sections of No. 1 mine are shown in the sketches (figs. 4 and 5). The headings are kept well in advance of-the main. stope except where the ore
face is low, when no stope is carried, and: the entire face.is. advanced by the same method as the heading. ore
The chert and ‘cceihs breccia breaks into large boulders, and it is necessary to do a ; considerable. amount. of "boulder. popping” before loading. All
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used, The headings are drilled from. a post, but the stopes are drilled from a. tripod. For ordinary work 33 per cent ammonia. powder is used, but, for wet work or where the ventilation is poor, gelatin powder of the same strength is used. The
cost of ammonia powder a $0.1266 — oui and the gelatin powder $0.1400 per for the eae 1928, ee 7
Under — Su ail “The mine is ‘supported almost nities by pillars of . ore from 20 to 60 feet in diameter, the average being 30 feet. The size depends upon the character of the ground and the height of roof. The pillars are: spaced 40 to 100 feet, center to center, with an average spacing of 80 feet. Wherever. the character of the ground permits, the roof is arched between a
Some of the pillars have been. trimmed down as small as was considered safe; these have shown no signs of taking weight. ‘At present the ‘pillars represent about 15. ‘per cent of the total area cut, but ‘many of these will.be recovered be-. fore the mine is abandoned. All pillars can not be recovered, for the mine is under the town of Picher and the surface must be protected,
There are parts of the mine where thick'shale or loose boulder. ground necessitates timbering, but generally these parts are not..ore-bearing and only . "pull" drifts are driven through them. This method of support is of minor. importance in the mining operations. .
Drilling And Blasting Practice
Compressors.~ Air is. furnished rn a central compressor plant serving several mines. The capacity of this plant is 9,380 cubic feet per minute. The individual compressors range in capacity from 1,080 to 700 cubic feet. The air ig maintained at 110 ee at the plant. 7
Now 1 mine consumes steal 1: 600 ‘cubic feet of air per minute. The pressure at the machines ranges from 85 to 90 pounds, the average being about 86 pounds.
Drills.~ The drills used are all of the heavy Leyner type, although several makes of machines are used, They are run from tripods or columns, All drills use 14-inch hollow-round steel. Jackhammers are employed for "boulder popping," using l-inch hexagon, hollow steel.
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Figure 6—Stope and heading rounds
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Inf, Cir, 6113
The standard cross bit with 18° taper and 1/4-inch difference in gauge is used for both the Leyner drills and the jackkammers. The steel lengths for the Leyner drills are 5, 7, 9, 11, 13, 15, 17, and 20 feet. The holes are started with 2 3/4-inch gauge or the 20-foot holes bottomed with 13-inch gauge. The jack- hammer steels are made up into 1, 3, and 5 foot lengths. ‘The holes are started with 2-inch gauge and the 5-foot Noles are bottomed with 13-inch gauge. The
steels are bitted and shanked underground at a central plant located near the material shaft. 7
The steel consumption is 0.073 pounds per ton of ore mined,
Blasting.- The blasting practice in the district is different from that at most metal mines; so the practice will be described in some detail.
The heading rounds are loaded with three-fourths of a box of ammonia powder, 12 to 14 sticks to the hole. When the ground is hard and tight and a six-. hole round is used, the holes are fired in the order shown in the diagram (fig. 6). In ordinary ground, No. 1 hole is omitted and No. 2 hole is placed vertically above No. 3. In this case No. 2 is the lead hole and the other holes are fired in the same. sequence as before, Where the face is less than 12 feet high only a head- ing round is useé@, All holes are stemmed, using a ee eer prepared for the purpose, :
For mine faces ranging from 25 to 40 feet high the round shown in the dia- gram is used, For mine faces above 40 feet two sets of splitters are used, making 6 splitters and 3 stope holes. ‘The slope of the stope is kept at an angle of about 45°, For the 40-foot face, which will be taken as a model in the following description, the collars of the splitter holes are about 20 feet horizontally be- hind the heading round, and likewise the collars of the stope holes are about 20 feet behind the collars of the splitters. Where the mine faces are lower the measurements are cut down accordingly. For faces over 40 feet high six splitter holes, in two rows of three each, and three holes are. used. In every case the burden is the same on each hole.
The splitter holes are three in number, one in the center and one on either Side, all in the same horizontal plane. These holes are drilled with a rise of 1 inch to the foot so that they can be readily washed of all rn after squibbing. The holes are drilled with 20-foot steels,
The stope holes are also three in and are placed vertically under the splitters. These holes are drilled down with the same fall that the splitters have rise, They are so located that the bottom of the hole will be below the grade of the drift so as to prevent high bottom.
Each splitter and stope hole is squibbed or chambered three times before the final charge is loaded. The first time 15 sticks of powder are used, The
Inf. Cir, 5113 —
hole is then disweady Washed and 24 hours later is shot with 30 sticks of powder. After again being thoroughly washed, the hole is loaded with from 45 sticks to l béx of powder, denending on the size of the pocket. The hole is once more thorough ly washed, preparatory to. loading the breaking charge. For this charge from.2 to
4 boxes of powder are used, The hole is very seldom loaded to the collar except where the ground at the Sollay is unusually tight because of soft or cavey ground between the collar and the pocket. All holes are stemmed, using a clay cartridge prepared from clay found.on one of the company's properties, The-cartridges cost about $0.01 each.
jn average. ae ar. i esti hole will. beehk about 250. tons of ore, The powder consumption is 0.75 panier ton.
A teediue. round wt ‘bveik 40 tone per machine ‘shift, and where hind and . splitter holes are used, 60 tons. per. machine shift are broken. For. high: headings (70 ft. ) 75 tons ak machine shift has been. broken,. so oe 7
- ‘Loading “And Tramming
All seals shee taal labor, ‘the Cars are of 20-cubic-foot aaiekiie wn average 1 ton of ore. The size of the car is 4 a 25 by 2 feet. The track gauge is oA. inches throughout the mine. - see oe ee
The Cars are gathéred on "lay-bys" or sidings near the techie face by trammers who help the shovelers with the loaded-cars,. One trammer. or "mule" is provided for every four shovelers. For short hauls miles are.used to bring the Cars to the shaft or hopper, but for long hauls electric locomotives of the trolle type are used, Three nules are used underground and two locomotives, each.of whic weighs 45 tons and is Gapable of handling 40 loaded’ cars. .
Trammers or "bumpers", take the cars from the "lay-bys" near the skip pocke (fig. 7) and dump the ore upon a srizzly made of 90-pound rails set 6 inches apar above the skip pocket. "Screen specs" sledge all boulders which will:not pass through the grizzly. CO a
AY) ‘ore mined on the: 200-foot level in the north part of the mine is dampe into an ore chute or hopper and drawn out on the main haulage level. This is the
only hopper in use at present. The hopper is a raise driven at an angle of 45° with the lower end equipped with gates for drawing off the ore, The gates are
raised and lowered by a simple lever arrangement, PUMPING
The only pumping necessary is from a sump which drains the skip pocket. The water level has been lowered for the district so that the main level is dry. To keep the sump dry, two small pumps with a combined capacity of 100 gallons per minute are run for about three hours each day.
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Ficure 7 Details of skip pocket and skip installation
Inf, Cir. 6113 LABOR EFFICIENCY, 1928
Racord of Labor Performed at Mine No. ae daly to to December, 1928
Total shifts for © Tong per” TMaMMOrs dasauseesseceetanteeeaes 2,12 ° 82,36 Drill runners and helpers ©. %,009 22.90 UNCKEES. <iweseutareseaweemwesuaces “2)000 19,65 Miscellaneous sececcreeeeeeees 9. 8,000 2 22.92. Total underground dietaltons ee - sal aa “Fe 8,91
Ore hoisted during last 6 months of 192e amounted to 68,770 tons. PERCENT AGh oF EXTRAG m1 10N
At neon 15 per. cent of the afea mined is left in pillars, “but it: is expected that after the mine- is: abaridoned 90 per cent of the ore, at least, will have been extracted and that most of the Semies Bone 10 per cent will. be in lean ore and will not represent a very great loss.
7. And Contract System
AL labor. ‘except ae is hanes on an ee i Muckers are paid on contract, 145. cents per car if they work iess: than 6:.shifts per week, and 153 cents per car if they work the full 6 shifts., When loading from a large pile, With little clean-up work, the average muicker will load 30.to 40: tons per shift...
The following wage schedule was in effect for 1928: when ‘zinc ore pee stayed at $40 or under for the year. - .4
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Machine runners 4,25 Machine helpers 93.76 PVSMMCT S seg seinen sad aes 3.00 Blacksmiths 0 4.20 HOLSUMON: 64. <.6.6:00s.e Ge 4,75 Locomotive operators .. 4.25 Locomotive brakemen ... 3.70 POWGEYMEN wecscscvceess 4.50 Roof trimmers 4.00 DCTOCONMAN: 66-66 %.4uee eee 3.00
This wage scale is based on $40 zinc ore, If the price goes above $45 and stays there for one week, all wages are automatically raised 25 cents per shift and muckers ave raised 1/2 cent on the car, Likewise for every $5 raise in the price . of ore above $45, the wages are raised at the same rate, but for every drop of $5 the wages are reduced accordingly. A week is always allowed between the wage changes to make sure that the market will not fluctuate above or below the critical rice,
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The ventilation is natural excépt:.in rare cases where a long drift is being.driven or an orebody opened up froma raise. . In such cases ventilation is supplied by small blowers driven by motors, Where the drift or orebody cuts a churn drili-hole,. this hole is cleaned out and the blower installed on the sur- face. If no drill hole is available, canvas tubing is used and the blower set out in the main workings. a
FIRE - HAZARDS. . So Little timber is used idiaiaedal that the fire hazard is practically nil. .In case of fire at the surface buildings, the workings are cut into other properties so that the men are never in danger.
SAPSTY... pee
; Much attention has been given to a during the past few years, The
company Maintains a fuli-time, safety engineer and assistant. The se men have full power to enforce any safety measure s ‘they deem necessary.
The Tri-State Zinc and Lead Producers Senet ute maintains ‘a full- time safety engineer to cooperate with and coordinate the work of the various Company men, A system of presenting flags to the various mines for not losing any time from accidents for periods of 3, 6, and 12 months has been inaugurated by the
/ association, This has aroused the:men's interest in safety measures, as is shown ‘by the fact that mines from this district won the Explosive Engineer's Safety
Trophy for the years 1926 and 1927 and that several mines from the district: were in. the runner-up list. for 1928,
The company further arouses the interest of the men - paying all ground - bosses a bonus of $25 for every month passed witnout a lost-time accident, and the mén are. given a pair of sable work sail
BIB i ee
Inf. Cir, 6113 MINING COSTS
Below is the total cost for delivering a ton of ore to the surface at No. 1 mine:
Cost of delivering 1 ton of ore to the surface at No. 1 mine
Cost Per cent
Total underground labor weeee $0,598 60.7 Supervision ee ee ee ee ee ee 026 2.6 Compressors, air drills, drill steel . Le? 12.9 Hlectric poWer wicccccessevcoece seco ates O41 4.2 Explosives ere re ee ee ee L10 li.2 OtheyY’ supplies: <c.4csvecneeas jSelewiewas 083 8.4
UO UCRL. COB be: say. Sar5:bece eres 6 eunwie ace ee ecereed $0.985 100.0
summary of costs in units of labor, power, and supplies, July to Dec., 1928
Name or number of mine - lio. 1 Year, 1928 - 6 months' operation Tons of ore mined and hoisted: 68,770
Mining metnod: Open stopes with pillar support
(A) Labor (man hours per ton):
Cost Per cent
Breaking (drilling and blasting) son eerie cece 0.9877 228.1 MUG IELTS teeing iyo ota tenes acanee-e ore Re ee re re re err are 0.407 30.4 Haulage and hoisting ee ee re ree eee 0.282 21.0 Supervision Scat ebiaiu ce. euaters ee ee ee ee ee 0.028 wel GONCUA. 2454600 e cnaee tae eee eoss eneeeee ie etal tae 0.247 18.4
Total labor underground ee ae ere a 1.541 100.0 Average tons per man per shift Tee ee wed Labor, vercentage of total cost hcacectcicene: oratories 63.35
(B) Power and supplies:
Explosives (lbs. per ton) - 33 ammonia and gelatin.. 0.750
Total power (hp. hrs. per ton) woccccccccsesssoccees 9.91 (1) Air compression A aeauennree ates 6,00 . (2) Hoisting ee eer ee ee 2.77 (3) Pumping ca.ccceiewnse cesses eweweesece Ovec (4) Haulage (includes: lighting) 0.92 Other supplies in percentage of total Supplies and power ...ccesnosccccssesscrccesseces 22 22.99
Supplies and power, percentage of totahkh cost 36,65
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