Arizona republican., 1918-03-24
Concentration and SmeItng at Hum boldt, Arizona
 By P. R, Miinesl

Consolidated Arizona Smelling con- | pany's plant at Humboldt, Arizona, IS treating 500 tons of ore daily and | producing therefrom about 1,S00,000 | pounds of copper per month. Ap- | proximately half of the copper pro- auction is from the ores of the com | panys mines, the Bluebell and the | De Soto and the balance from cus tom material. The ore deposits of the two com 1 pany mines are of the same type, 1 replacements in schist by chalcopyrite | and pyrite accompanied by secondary sillclfications. In physical character lstlcs the ore bodies are rather chim- neys than lenses; in the Bluebell mine six ore bodies are being worked and Tn the De Soto also six, which have persisted with practically the same dimensions on each level from the surface to the deepest workings 1900 feet in the Bluebell and 800 feet in the De Soto.
 The Bluebell ore bodies vary i'll length from 100 to 400 feet and in width from to 25 feet. Two sys- tems of mining are in use, "cut and filI' and overhaul stoping on ore, or 'shrinkage stoping," the latter method predominating and the former being employed only where the stope walls are bad, due to severe faulting. The ore is hoisted to the surface in skips through a three compartment shaft and dumped into bins from which it is drawn for the buckets of the aerial tramway to be carried | three miles to the railroad. There it is loaded in 40 ton cars for the F mile haul to Humboldt over the q i,1cr lA,-r,, ,,oI, Nn | system.
 The Bluebell mines present produc- i ton is 10000 tons of ore per month and the mining cost, including de- velopment, is s2.75 to $3O0 per ton F. o. B. cars Bluebell Siding.
 The De Soto mine is worked through a 2000 foot adit which cor responds to the 600 foot level of the mine. Five levels have been opened above the adit and two be- low it, and the mines production of l 150 tons per day is hauled by mules from ore pockets on the adit level l to the bins at the upper terminal of | the aerial tram, distance of 2300 feet. The tram line is 4000 feet long and operates by gravity, there be- ing a difference in elevation of | 1000 feet between the two terminals. In addition to overcoming friction and pulling up the empty buckets, considerable energy is absorbed by brakes. This energy will shortly be utilized as electric power by gearing a motor to the bull wheel, which motor may be reversed and operated as a generator delivering as electric energy the surplus power, which serves now only to heat the friction brakes.
 The De Soto ore bodies vary in length from 30 to 120 feet and in width from 5 to 40 feet. The walls stand firmly and "shrinkage" stoping is the only method employed. The mining cost, including development, sorting and tramming is s2.55 per ton; freight to Humboldt (25 miles distant) is 70 cents, making the ore cost S325 per ton F. o. B. Humboldt. Both at Bluebell and De Soto the ore is run over a sorting belt before loading from to per cent of the tonnage is discarded as waste.
 Concentration
 At Humboldt are the concentrating mill and smelting plant. The concen- trator capacity 800 tons per day, treats exclusively the more silicious ore from the Bluebell and De Soto mines. No custom ore is milled and the oXidiZed domestic ore and more basic domestic ore are likewise sent direct to the furnaces. The De Soto ore is all very siliceous, containing 65 to 75 per cent insoluble and is all sent to the concentrator; but much of the Bluebell ore is quite basic and it is more profitable to smelt the l ha centage of insoluble runs below SO This is particularly the case since the precious metal values are greater in the more basic ore and the re- covery of these is better in direct smelting than in concentration fol- lowed by smelting.
 The ore is delivered in bottom dump railroad cars at the top of the concentrator building and discharged into the 125 ton bin supplying the crushing plant. A short conveyor belt takes the ore to a 12x24 inch Blake type breaker that reduces it to inches. The breaker product dis charges on to a 20 inch conveyoI belt leading to the Symons (4Sinch diameter) disc -crusher. This con- veyor is equipped with a Ding mag netic pulley to pick out drill bits hammer heads and other iron and steel pieces that would otherwise find their way into the Symons crusher. In spite of this precautior steel occasionally gets into the crush CT, causing chokeups that require from half an hour to several hour. to clear and threatening always serl- ous damage to the machine.
 From the Symons crusher, the ort fo int a bucket elevator which raises it t a 7x3 foot trommel covered with ]: inch punched plate. The undersize il conveyed by a 20 inch belt to tn 600 ton crushed ore bin furnishin: storage for the concentrating sec tion. The oversize drops to a SC of 40x16 inch Anaconda type roll sent to 14 inch and the discharge 0 rolls is led to the bucket elevate mentioned above. The oversize i thus kept in closed circuit with tn rolls until crushed free enough t pass the trommel screen whereupol it is conveyed to the crushed or bin.,
 From the crushed ore bin the ore now reduced to F inch is drawn a required for the ball mills by tw apron feeders, discharging onto 2 inch conveyor belt. This belt run over a Merrick weightometer wit automatic register, recording the ton mage passing over it: At the head c the belt is a splitter to proportio the feed as desired between tn two ball mills. One ball mill an Allis Chalmers, 6x6 feet cylinderi cal mill from which the grating a the discharge end has been removed The other is a Hardinge mill 6x2 inches. Both mills are driven b spur gears on countershafts belt con nected to motors and grind in ope