CHAPTER XY. 



THE LESSER METALS, CONTINUED MERCURY, NICKEL AND 

 COBALT, PLATINUM, TIN. 



MERCURY. 



2.15.01. Ores : Cinnabar, HgS. Hg. 86.2, S. 13.8. Metacin- 

 nabarite is a black sulphide of mercury. Native mercury also 

 occurs. 



Mercury deposits are found in workable quantities in the 

 United States only in California, in Oregon, and in one locality 

 in Nevada. , In all cases cinnabar is the principal ore. The Cali- 

 fornia deposits are limited to the Coast range and in their forma- 

 tion seem to have followed great basaltic eruptions of post-Plio- 

 cene age. 



2.15.02. Example 50. New Alinaden. Cinnabar with sub- 

 ordinate native mercury, in a gangue of crystallized and chalce- 

 donic quartz, calcite, dolomite, and magnesite, forming a stockwork, 

 or "chambered vein," in shattered metamorphic rocks (pseudo- 

 diabase, pseudo-diorite, serpentine, and sandstone). There are 

 two main fissures, making a sort of Y, with a wedge of country 

 rock between. The ore bodies are in the fissures and also in the 

 intervening wedge, and have associated with them much attrition 

 clay. A great dike of rhyolite runs nearly parallel to the fissures, 

 and to this Becker attributes the activity of circulations which 

 filled the vein. New Idria is farther south, high up toward the 

 summit of the Coast range. The ore is deposited in shattered 

 metamorphic rocks of Neocomian (Lower Cretaceous) age, and in 

 overlying Chico beds. The ore is accompanied by bitumen. Ba- 

 salt is abundant ten miles away. North of San Francisco other 

 mine have been opened, among which are the Oat Hill, Great 

 Eastern, and Great Western. The mines are in a region pierced 

 by eruptions of basalt and andesite, which doubtless gave impetus 



