94 IT. Lindgren — Gold Deposit at Pine Hill, Cal. 



Hill forms the cumulating point. Surrounding the latter 

 there is an area of intense decomposition, somewhat ill de- 

 fined but approximately one mile long and from one to two 

 thousand feet wide, of a very different character from the 

 ordinary chloritization and uralitization. The rocks within 

 this area are converted to a soft, porous, reddish brown to 

 yellowish mass, from which calcium, magnesium, iron and the 

 alkali metals together with a part of the silica are removed ; 

 the ultimate product of this decomposition, which I think 

 should be regarded as having been effected by thermal waters, 

 alkaline in character, is a soft white nearly pure kaolin* or 

 hydrated silicate of aluminium. If there exists a large quan- 

 tity of this pure white kaolin it could no doubt be utilized 

 for keramic art; the somewhat impure substance would do 

 very well for the manufacture of ordinary pottery. 



In many places the zone of decomposed and kaolinized 

 diabase is impregnated with irregular veins and seams of barite 

 or heavy spar, and with this mineral the gold is closely con- 

 nected. The largest barite mass appears on the northeast side 

 of the hill and about three hundred feet from the crest ; a 

 shaft fifty feet deep was sunk here a few years ago and some 

 ore extracted. The deposit not being worked at the time of 

 my visit, the shaft was inaccessible. It did not appear as if a 

 well defined and extensive vein of barite were present, but 

 rather as a local enlargement of one of the numerous smaller 

 irregular barite seams. The ore on the dump was largely 

 composed of barite mixed with limonite and decomposed 

 country rock. !No sulphurets, but a few stains of sulphate of 

 copper were noticed. Although no normal vein quartz occurs, 

 there are in various places seams and smaller masses of a fine 

 granular aggregate of quartzitic appearance but doubtless due 

 to secondary processes. Assays were made on a series of 

 specimens, both of ore and country rock, by Dr. W. H. 

 Melville, in the laboratory of the U. S. Geological Survey. 

 Special precautions were taken to insure correct results and 

 the exceptionally pure litharge used contained only 2 cents of 

 silvertto the ton. 



The assays in general show a large relative amount of silver 

 — more than is usual in the gold quartz veins. The proportion 

 of gold to silver by weight varies from 1 : 1 down to 1 : 5, or 

 in value from 20 : 1 to 4:1. The metal resulting from the 

 reduction of this ore would be a dore bullion similar to that 

 yielded by the Bodie (Mono County) quartz veins. 



The assay of the ore from the dump, composed of barite 



*In a specimen of this white substance the water was determined quantita- 

 tively by Dr. E. A. Schneider, who obtained almost exactly the theoretical amount 

 for kaolin, viz: 13*8 per cent HoO. 



