IF. Lindgren — Gold Deposit at Pine Hill, Gal. 95 



and some limonite, gave a paying amount of gold with silver 

 in the proportion of 1:2 by weight ; a piece of very pure 

 white barite selected for the purpose, and shown under the 

 microscope to contain no visible gold or sulphurets, gave the 

 same amount of gold, but much more silver, the proportion 

 between the two metals being 1 : 5. Only a part of the silver 

 exists as an alloy with gold, for a pan of the ore washed out 

 gave a considerable quantity of quite yellow gold in very fine 

 particles ; hence it may be permitted to surmise that the silver 

 partly occurs as a chloride. A piece of barite with much lim- 

 onite gave an exceptionally high return with but little silver, 

 the proportion being 1 : 1. 



Near the crest of the hill there are several little prospect 

 holes in the decomposed mass. One specimen shows a brown- 

 ish to gray compact decomposed rock permeated with little 

 seams of barite. This gave 0-063 oz. gold and 0*163 oz. silver 

 to the ton, or $1.26 in gold and $0*16 in silver, the proportion 

 in weight being about 1 : 3. 



A specimen from the summit of Pine Hill is a soft crumb- 

 ling mass largely composed of kaolin, pink or yellow in color 

 and showing on fresh-fractured surfaces traces of the grain of 

 the original rock.^It was not expected that this mass would 

 yield any results, but it proved to contain 0*0375 oz. gold, and 

 O'OTo oz. silver per ton, or respectively $0.75 in gold and $0.07 

 in silver. No barite is visible in the rock, but a quantitative 

 determination by Dr. E. A. Schneider showed it to contain 

 0-34 per cent BaS0 4 . 



At the southeast end of the decomposed area a shaft has 

 been sunk to a depth of about one hundred feet, and traces of 

 gold are reported to have been found. 



It is thus reasonably certain that this whole altered mass of 

 diabase and porphyrite is auriferous ; that barite in vei*y vary- 

 ing quantities is distributed through it, and that the quantity 

 of the gold contained is approximately proportional to that of 

 the barite, or, in other words, that the barite acts as the car- 

 rier of the gold. The primary mineral combination was prob- 

 ably native gold, pyrite, rich silver ores, and barite. 



Whether the kaolinized zone is connected with large fissures, 

 it is not possible to say from the present slight underground 

 developments ; on the surface, at least, there are no indications 

 of such a connection, yet a channel must have existed for the 

 passage of the waters effecting this far-reaching alteration of 

 the rocks. 



In the foothills of Yuba County and also in massive diabase 

 there is a zone of extreme decomposition resembling some- 

 what the one here described, but associated with a considerable 

 amount of secondary, fine grained, quartzose and chalcedonic 



