CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
177 
The following rocks are from Shasta County, but not within either 
the Mount Shasta or the Lassen Peak areas. Collected by J. S Diller 
who furnishes the petrographic data. 
A Dacite-porphyry, east fork of Clear Creek, 9 miles above French 
Uuich. Contains conspicuous phenocrysts of plagioclasc, a few of 
quartz, and smaller ones of biotite and pyroxene, in a groundmass of 
quartz and feldspar. Analysis by J. K. Whitfield, record No. 970 
B. Dacite-porphyry, Smiths Gulch, 6 miles up Clear Creek from 
Brench Gulch Contains phenocrysts of plagioclasc, quartz, bio- 
Me and hornblende in a groundmass chiefly of quartz and feldspar. 
t^SoX S. ltfle P d k N c°: 9o L Also dcscribed by J R Iddi ^ >" 
eeo'i-d^oinW 1 " 0n °' N<>t d6SCribed - Anal y sis h y T - M - Chatard, 
A. 
B. 
c. 
Si0 2 .... 
66.30 
17. 55 
2.19 
.55 
.97 
3.12 
5.15 
2.45 
1.25 
trace 
.15 
trace 
64.24 
18.67 
1.40 
1.96 
1.48 
4.11 
4.14 
1.71 
1.18 
.76 
.08 
trace 
68.10 
15.18 
1.34 
1.70 
2.06 
4.66 
3.71 
. 1.48 
.55 
.35 
.18 
.20 
.06 
A1 2 3 
Fe 2 3 .__. 
FeO_... 
MgO .... 
CaO 
Na 2 
K 2 
H 2 
Ti0 2 
P 2 5 
MnO .... 
BaO 
S0 3 
.28 
.22 
.25 
CI 
Less 
99.96 
100. 20 
.05 
99.57 
100. 15 
2. LASSEN PEAK REGION. 
iRocks collected by J. S. Diller, who has furnished the petrographic 
ta Nearly a ii are from the ^ ^^ hy ^ ^^ ^^ 
let of the US. Geological Survey. The quartz basalts have been 
scribed by Diller in Bull. 79, and partly in Amer. Journ. Sci., 3d 
les, vol 33, p. 49. The analyses arc so numerous that it seems best 
divide them into subordinate groups. 
Bull. 168 12 
