GOLD MINING IN COLORADO. 525 



depth just named. From these developments the vein appears to have a 

 course of north 60° east, true, though its average course for a longer distance 

 than that observed is said to be more to the eastward, and thus more nearly 

 parallel with the other neighboring lodes further south, that trend north 85° 

 east. Its dip is to the south 84°, and so far as sunk upon is very regular. 

 The average width is about two feet, frequently expanding or contracting to 

 greater or less dimensions. Its walls are generally smooth and well defined, 

 sometimes polished, grooved, or striated, showing indications of movement. 

 Usually there is a soft " gouge," or seam of clay between the walls and the 

 filling of the vein. The latter is chiefly quartz ; sometimes white, hard, and 

 amorphous, carrying little orno valuable mineral; sometimes showing a sparse 

 distribution of crystallized iron pyrites throughout its mass; but most com- 

 monly the vein-matter is a mixture of siliceous and feldspathic material, in 

 which occur small seams or scattered particles of pyrites, making a very fair 

 quality of stamp-rock, and, as in the other veins already described, associated 

 usually with a narrower but solid seam of compact pyritous ore. The latter 

 is from two or three to ten or twelve inches thick, and furnishes a small pro- 

 portion of smelting ore. This proportion appears, from all available data, to 

 be between one-twentieth and one-tenth of the whole number of tons pro- 

 duced. The valuable mineral in the vein consists chiefly of iron pyrites, with 

 a lesser proportion of copper pyrites and, as a characteristic feature, some 

 arsenical pyrites; with these are associated some zincblende and galena. The 

 yield of this ore in silver is shown by the assays of Professor Hill to be larger 

 than is usual in the pyritous ore veins of the district, the average of 42 tons 

 sold by the mine at the Smelting Works, during the summer of 1868, being 

 about four ounces of fine gold and twenty ounces of fine silver to the ton. 

 The yield of stamp-rock during a run of thirty -four weeks in the summer of 

 1868, when 200 cords, or 1,500 tons, were supposed to have been treated, 

 was 1,538 ounces of crude bullion, or about one ounce per ton. The average 

 value of the ounce of this bullion is stated at $15 50, coin. 



The filling of the vein is generally soft, so that much of it may be 

 removed with a pick, requiring comparatively little blasting. This facilitates 

 considerably the working of the ground, both drifting and stoping being done 

 for somewhat lower prices than in the majority of the veins in the district. 



