546 MINING INDUSTRY. 



CoALEY AND GiLPiN LoDES. — Although the mineral veins of Gilpin 

 County are chiefly valuable for their gold, there are some, as has been already 

 shown, that carry a considerable proportion of silver. In addition to these 

 there are a few that are only valuable for silver and which possess no gold at 

 all, or so little that it is practically unimportant. The development of these 

 silver veins has not progressed very far, but within a year past they have 

 attracted increased attention and are now of growing importance. The 

 Coaley and Gilpin lodes are among the more recent and valuable discoveries 

 of this class of veins. They are situated in Slaughter House Gulch, a ravine 

 on the north side of Clear Creek, a half mile or more below Black Hawk ; 

 they were opened late in 1868. 



The Gilpin apparently crosses the ravine with a northeast and southwest 

 course, dipping almost vertically. It is opened by a tunnel on the west side 

 of the gulch, about 200 feet in length. The Coaley crops out about 60 or 70 

 feet south of the mouth of the Gilpin tunnel. Its course is nearly east and 

 west and its dip is to the north at about 30° from the horizon. The two 

 veins, therefore, intersect each other. The work done upon them thus far is 

 not sufficient to determine positively whether they are independent veins or 

 one of them a branch of the other. The depth reached in August, 1869, 

 did not exceed 40 feet. 



The inclosing rock is of the same gneissic or granitic character which 

 prevails in this district. The walls of the vein, where visible, especially the 

 north wall of the Coaley, are pretty well defined ; the crevice is not large in 

 either vein. The gangue is chiefly quartz ; the ore consists of galena and 

 zincblende, both apparently argentiferous, a little copper and iron pyrites, 

 argentiferous sulphurets, and native silver. The latter, in some selected speci- 

 mens, is very abundant. Some of the assays of this ore show a very high 

 value in silver but no gold. Seventy-three tons of this ore, sold for smelting, 

 contained, on the average, 215 ounces of fine silver per ton, 



