CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
245 
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 districts 
north of San Francisco. 
A. Psendo-diabase, near Mount St. Helena. Ornose. Contains 
augite, hornblende, oligoclase, albite, zoisite, ilmenite, leucoxene, and 
a little chlorite. 
B. Pseudo-diabase, Sulphur Bank. Ornose. Contains oligoclase, a 
little quartz, pyroxene, hornblende, ilmenite, sphene, serpentine, and 
chlorite. 
C. Pseudo-diorite, Knoxville. Rossweinose. Mainly actinolite, 
with a little white mica, chlorite, serpentine, sphene, rutile, and zircon. 
D. Glaucophane-schist, Sulphur Bank. Mainly glaucophane and 
zoisite. Quartz, albite, muscovite, and sphene are also present. 
Si0 2 .. 
A1A- 
FeA 
FeO.. 
MgO . 
CaO.. 
Na,0. 
H 2 Oatl00°_... 
H 2 above 100° 
TiO, 
Cr 2 3 - 
MnO. 
MO.. 
A. 
49.08 
14.68 
1.95 
9.63 
6.69 
10.09 
4.60 
.20 
.27 
1.18 
1.72 
.23 
L5 
100. 4; 
]',. 
51. 28 
15. 05 
2.42 
8.01 
6.07 
7.08 
4.43 
.12 
.39 
2.96 
1.33 
.13 
.25 
.10 
99.62 
C 
50.44 
8.18 
1.06 
6.29 
17.63 
11.55 
2.98 
.50 
.07 
.92 
.48 
.21 
100. 31 
49.68 
13.60 
1.86 
8.61 
6.26 
10.97 
3.09 
.12 
3.84 
1.31 
.21 
.04 
99.59 
