90 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[no. 228. 
H. Dark vitreous quartzite. Contains quartz, a little red feldspar, 
some chlorite, some green mica, a few scales of biotite, and grains of 
magnetite. P. R. C. 1007. 
I. Lighter interbedded quartzite. Feldspar in it much altered. 
P. K. C. 1004. 
J. Epidotic quartzite. P. R. C. 1023. 
K. Unaltered quartzite. P. R. C. 1000. 
Analyses by R, B. Riggs, record Nos. 569, 571, 572, 575. Material 
dried at 105°.' 
Si0 2 . 
A1 2 3 
Fe 2 O s 
FeO. 
MgO 
CaO. 
Na 2 
K 2 0. 
Ign . 
Ti 2 
MnO 
74.22 
10.61 
7.45 
.85 
1.48 
.56 
2.12 
1.08 
1.79 
.16 
none 
100.32 
73. 65 
11.08 
7.24 
. 77 
1.52 
.40 
1.67 
1.65 
1.88 
trace? 
trace 
99. 86 
73. 14 
12.60 
7.57 
1.31 
1.67 
.43 
1.78 
1.00 
.83 
.04 
trace 
100. 37 
K. 
73.64 
11.25 
6.24 
1.04 
1.57 
.36 
3.04 
1.42 
1.98 
trace 
none 
100. 54 
Ba and Sr not looked for. 
