ACADEMY OF NATURAL SCIENCES. 851 



At "Whisky Hill, a mill of forty stamps has been set up which is now running 

 with satisfactory returns. The cost by contract of delivery of the ores to the 

 mill, being stated at forty cents (40c.) per ton, the cost of mining and treat- 

 ment in mill being considerably less, it is said, than one dollar per ton, the 

 amount treated being five tons to each stamp. 



The chemical results of the extensive decomposition of metallic sulphids 

 which has in former times occurred at these localities, offer an interesting prob- 

 lem in chemical geology. The sulphur has been removed chiefly as sulphuric 

 acid beyond doubt, which has combined with iron and copper to form sulphates 

 of these metals. These have for the most part disappeared, being washed out 

 by the atmospheric waters, and have followed the drainage of the country. 

 At Whisky Hill I found the sulphate of iron, (Coquimbite) sulphate of cop- 

 per, (Cyanosite) and alum. The water of the shaft contains copper enough to 

 redden the iron tools. At Quail Hill considerable masses of heavy spar are 

 found, formed probably from the action of soluble sulphates upon witherite. 

 No gypsum was observed at either locality. 



The mineral species observed at Whisky Hill, are as follows : 



Metallic Gold. 

 Metallic Copper. 

 Metallic Silver. 

 Red Copper. 



Malachite (Green Carbonate of Cop- 

 per). 

 Azurite (Blue Carbonate of Copper). 

 Chrysocolla (Silicate of Copper). 

 Cyanosite (Blue Vitriol). 

 Copper Glance (Vitreous Copper). 

 Zinc blende. 



Galena. 



Iron pyrites. 



Alum. 



Coquimbite. 



Heavy Spar. 



Hematite (chiefly the earthy varieties). 



Kaolin. 



Lithomarge and various aluminous and 

 magnesian silicates resulting from 

 the decomposition of the chloritic 

 aud talcose rocks. 



The list of species is about the same for the deposit at Quail Hill. 



The line of division between the ore-bearing ground in these great ore chan- 

 nels, and the country rock is quite distinctly seen on both the eastern and west- 

 ern outcrop at Quail Hill, and on the western at Whisky Hill. At the former 

 place it is a dark bluish porphyritic rock, probably metamorphic, of a sandstone 

 or silicious sediment. The outcroppings resemble those of many quartz veins, 

 and I find the moss-covered portions of this quartzose matter full of cavities, 

 resulting from the decay of pyrites, and yielding, by assay, three to five dollars 

 to the ton in bullion. 



From all the evidence presented, we seem justified in regarding these remark- 

 able metallic deposits as segregated veins, holding a pretty uniform and high 

 tenor of gold aud silver, associated with and derived from the decomposition of 

 extended masses of metallic sulphurets and quartzose matter, and carrying at 

 times, ores of copper, the commercial value of which is, however, entirely subor- 

 dinate to that of the precious metals which are found to characterize these veins 

 or ore channels. 



San Francisco, April 15th, 1867. 



