140 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
The cost of treatment is somewhat difficult to arrive at, as few figures are 
published. The Portland mill places the cost of chlorination at about S3.70 per 
ton. Mr. T. A. Rickard states that in one of the large mills the cost reaches S3.46, 
which will probably be increased to S4 per ton with charges for depreciation and 
general expenses added. Roasting alone costs from 45 to 60 cents per ton (Rickard). 
In the opinion of some able metallurgists the cyanide process is much better adapted 
to the ores and will eventually displace chlorination; they claim that the cost 
should not exceed $2.50 per ton, including amortization of capital invested." 
Cyaniding without roasting is practiced in two mills at Cripple Creek which 
handle low-grade and entirely oxidized ores. In this case mining costs are low 
and ore containing $5 per ton should yield a fair profit. The extent of these ore 
bodies, chiefly located on Globe and Ironclad hills and at Copper Mountain, is as 
yet more or less problematical. The breccia is thoroughly oxidized on Globe 
Hill, in places to a depth of over 800 feet, and it is not impossible that good-sized 
ore bodies of low grade may be encountered in this vicinity. Up to date the 
fairly extensive exploration has not been rewarded by corresponding development. 6 
TECHNICAL DETAILS. 
At present the Dorcas mill, at Florence, is the only cyanide plant treating the 
ordinary telluride ores. Much of the ore is of remarkably high grade, averaging 
4 ounces per ton; it is largely obtained from the C. K. & X. mine. After passing 
through rock breaker, three sets of rolls, and a drier the ore is roasted in a Holthoff 
automatic oil-burning furnace, from which it is conveyed to bins. There are 
twelve 140-ton steel leaching tanks about 30 feet in diameter. The solution 
used is naturally strong, the different grades ranging from 0.6 to 0.8 per cent. 
The percolating gold solution is precipitated in boxes with zinc shavings. Tailings 
are passed over Wilfley tables, on which a considerable amount of coarse gold is 
saved. 
The different chlorination plants use practically identical processes. 
A type is the Standard plant of the United States Reduction and Refining 
Company at Colorado City, which treats Cripple Creek ores exclusively, has a capacity 
of 450 tons per day. All the ore received goes to the sampler. The ore is there 
crushed to three-fourths inch mesh and one twenty-fifth of it taken out for finer 
crushing and quartering for the assay and analysis sample. Belt conveyors take 
the ore from the sampler to the bedding room, where it is loaded from hoppers into 
cars and thence dumped in heaps on the bedding floor below. With ore of ordinary 
grade sufficient homogeneity of the mixture is secured by dumping alternately 
on different heaps small carloads from different shipments. But high-grade ores 
are mixed more carefully with those of lower value. 
From the bedding floor the ore is taken b} T belt conveyors to the driers—long 
tables where the ore is moved by mechanical rakes and heated only sufficiently to 
drive off mositure. It is next trammed to hoppers, whence it goes to the rolls to 
a Argali, Philip, Chlorination r. cyanidation: Eng. and Min. Jour., November 24,1904. For further contributions to the 
same subject see Greenawalt, W. E., Eng. and Mm. Jour., October 27, 1904; and Doveton, G. D., The metallurgy of 
Cripple Creek, Colo.: Min. Jour. (London), December 23, 1905. 
b At the end of 1905 five small plants with individual capacities up to 150 tons were in operation. 
