HISTORY AND TECHNOLOGY OF THE GOLD DEPOSITS. 
137 
The ore from the various stopes is not separated but dumped in two bins after 
passing over 1-inch grizzlies. The hand sorting is done at six tables with four 
men at each. The waste from the sorting,slides down over an inclined 15- by 4- 
foot sheet-iron plate perforated with half-inch holes and is continually sprayed in 
order to wash off the fines. Before going to the dump the waste from the washer 
is finally picked over on a belt conveyor. 
At the Mary McKinney mine the ore from the stopes is shoveled into a Crane 
washer, a local invention composed of a 46-inch by 15-foot trommel with three- 
fourths inch holes, separating out the dry fines. The coarse is discharged into a 
smaller strongly inclined and perforated trommel about 15 feet long, the near end 
partly submerged in a tank of water. By this device the ore is washed, the fines 
falling into the tank and the coarse being carried up by means of an endless screw 
and discharged at the higher end of the trommel on a conveyor belt 50 feet long 
and 20 inches wide, on which the ore is sorted by five men. The capacity is said 
to be 100 tons per eight hours. 
At the El Paso mine ten bins are used and the ores from various stopes are 
kept apart. The classification is effected by two or three parallel screens under a 
protecting 3- by 15-foot grizzly, with bars 4 inches apart. The first screen has 
1-inch perforation, the second three-fourths inch. The dry fines below three- 
fourths inch average $75 per ton, those between 1 inch and three-fourths inch $25. 
From each bin the ore slides down on a sorting table, while sprays wash off the 
remaining fines, which are collected in tanks. These fines are of very high value. 
Ten sorters are employed. The present output (March, 1904) is 50 tons per day. 
In former j^ears the sorting of the ore was much neglected, as evidenced by 
the numerous rich dumps in the camp. Even now the arrangement at many 
mines is imperfect. 
The cost of mining is, as a rule, very high, though few accurate data are avail¬ 
able on this subject. Mr. J. R. Finlay/' the former manager of the Portland mine, 
makes the following statement, which is well worth quoting: 
A study of the situation shows that these high costs result from the amount and character of the waste 
that must be handled with the ore. As is well known, the largest ore bodies of Cripple Creek are not solid 
masses of uniformly valuable mineral, but contain volumes of rock into which the gold-bearing solutions have 
penetrated along multitudes of crevices. The problem of getting the best results in such veins is essentially 
one of concentrating the values. The peculiar character of the ore renders concentration difficult, if not 
impossible, by any method other than hand sorting. Ordinarily the concentration of ores may be effected 
cheaply by mechanical means, depending on the difference in specific gravity between the valuable and the 
worthless minerals. In the case of Cripple Creek ores this difference can not be depended upon. When the 
rock is blasted, a large part of the valuable material in the seams is reduced to an extremely fine powder, 
practically the lightest part of the mass; another part of the values will adhere to the rocks, while another 
small part is probably heavier than the average. 
The total cost of mining, including sorting and development work, is probably 
nowhere in the district—in the deep mines—less than $8 per ton and in many 
cases it may be considerably higher. The actual stoping cost in the Portland 
mine averaged about $3 per ton in 1902, and for 1903 is reported as averaging 
$2.19. 
a Ninth Ann . Rept. Portland Gold Mining Company, p. 16. See also Finlay, J. R., Mining costs at Cripple Creek: Eng. 
and Min. Jour., November 21, 1903. 
