CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
211 
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 arc from the districts 
north of San Francisco. 
A. Pseudo-diabase, near Mount St. Helena. Contains augite, horn- 
blende, oligoclase, albite, zoisite, ilmenite, leucoxene, and a little 
chlorite. 
B. Pseudo-diabase, Sulphur Bank. Contains oligoclase, a little 
quartz, pyroxene, hornblende, ilmenite, sphene, serpentine, and 
chlorite. 
C. Pseudo-diorite, Knoxville. 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 .. 
AlA- 
Fe 2 3 
FeO.. 
MgO. 
CaO.. 
Na 2 . 
H 2 at 100° 
H 2 above 100 c 
Ti0 2 
PA 
Cr 2 3 
MnO 
NiO 
49.08 
14.68 
1.95 
9.63 
6.69 
10.09 
4.60 
.20 
.27 
1.18 
1.72 
.23 
i'.. 
.15 
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 
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 
3.84 
1.31 
.21 
04 
99.59 
