160 ANALYSES OF ROCKS AND MINERALS, 1880-1908. 
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13. THE QUICKSILVER REGION. 
Rocks described by Becker in Mon. XIII. Analyses made by W. H. Melville in 
the San Francisco laboratory. With one exception (the serpentine from New Idria) 
all the rocks are from the distriets north of San Francisco. 
A. Pseudodiabase, near Mount St. Helena. Ornose. Contains augite, hornblende, 
oligoclase, albite, zoisite, ilmenite, leucoxene, and a little chlorite. P. R. C. 1459. 
B. Pseudodiabase, Sulphur Bank. Ornose. Contains oligoclase, a little quartz, 
pyroxene, hornblende, ilmenite, sphene, serpentine, and chiorite. P. R. C. 1460. 
C. Pseudodiorite, Knoxville. Rossweinose. Mainly actinolite, with a little white 
mica, chlorite, serpentine, sphene, rutile, and zircon. P. R. C. 1461. 
D. Glaucophane schist, Sulphur Bank. Mainly glaucophane and zoisite. Quartz, 
albite, muscovite, and sphene are also present. P.R. C. 1462. 
99. 62 
E. Andesitic obsidian, Clear Lake. Liparose. Shows grains of plagioclase, augite, 
and hypersthene. Sp. gr., 2.391. P. R. C. 1463. 
F. Andesite (asperite), Clear Lake. Yellowstonose. Contains pyroxene, plagio- 
clase, magnetite, and sometimes biotite. Pyroxene mostly rhombic. Sp. gr., 2.664. 
P.R. C. 1464. 
G. Obsidian, south of Borax Lake. Varingose. Sp. gr., 2,390. P. R. C. 1465. 
H. Basalt, south of Burns Valley. Andose. Rich in olivine, with a microlitic 
groundmass of plagioclase and augite. Sp. gr., 2.380. P. R. C. 1466. 
I. Ordinary basalt, Knoxville. P. BR. C. 1467. 
