146 
ANALYSES OF RJCKS, U. S. GEOLOGICAL SURVEY. 
--• 
H. Feldspar-porphyry, dike below Castle. Lassenose. Contains 
orthoclase, less plagioclase, hornblende, biotite partly altered to 
chlorite, sometimes allanite, and occasional iron ore. apatite, and 
zircon. P. R. C. 
I. Rhyolitic tuff, near fork- of Checkerboard Creek. Contain- frag- 
ments of shale, quartz, plagioclase, sanidine, and hornblende, in a 
brownish material carrying pumiceous glass. Much decomposed, with 
formation of kaolin. P. K. C. 562. 
.T. Svenitic mass included in granite, head of Cottonwood Creek. 
§ . Contains orthoclase, plagioclase, quartz, hornblende, biotite. 
apatite, and iron ore. A hornblende-mica-syenite. P. K. C. 554. 
K. Diorite, between Blackhawk and Robinson. Andose. Contains 
plagi lase, se, [uartz, biotite, diallage, hypersthene, iron orej 
apatite, and zircon. P. R. C. 559. 
L. Basalt, Volcano Butte. V *. Contains labradorite, augite, 
olivine, a little serpentine, occasional quartz grains, small patches 
glass, iron ore. chiefly ilmenite, apatite, a trace of calcite, and a 
mineral which may be nephelite or analcite. P. R. C. 565. 
M. Ajigite-vogesite, dike on west side of upper Fonrmile Creek. 
Kent . Contains augite, hornblende, iron ore. a little plagio- 
clase. orthoclase, calcite, and -fine decomposition products. P. R. C. 
N. Monchiquite-like dike rock, west side of upper Willow Creek. 
. Contains augite, olivine, biotite ilmenite, and a colorless 
- which appear- to be partially zeolitized glass. Also a little 
serpentine, chlorite, and calcite. P. R. C. 5»;4. 
- 
61.21 61.87 56.8 46.55 

FeA 
Fe<:» 1.^3 
1.54 


K 2 3.15 
H.m L43 


X 
MnO trace 
i.v i 

- 
58 
- S 
1.57 
- 71 
- 
17.26 
- - 
- - 
32 
9 
. 87 
trace 
9 
1.64 
" 58 
5.31 
28 
.46 
.10 
trace 
trace 
18 
4.40 
" 
58 
9. 49 
3.12 
1 . 55 
1.79 
2. 98 
.83 
.73 
.11 
trace 
trace 
45. 15 
15.39 
2. 76 
5.64 
9 
9 B 
2. 67 
2. 77 
_ - 
2.80 
42. 
12. 
3. 
5. 
12. 
12. 
1.21 
2.68 
4.03 
2.47 
.84 
. 14 
trace 
4.27 
.16 
trace 
. 55 
- 
I 
_ 2 
- " 
38 
- 
- 
2. 7i i 
99.51 
2.94 
.rated rare earths or metallic acid-, such as columbic. tantalic, etc. 
