54 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [no. 228. 
3. GRANITE AND GNEISS. 
For descriptions see Williams, 15th Ann., p. 657, and Keyes, ibid., 
p. 685. The Rowlandsville granite is described by Grimsley in Journ. 
Cincinnati Soc. Nat. Hist., vol. 17, p. 78. 
A. White granite, Brookville, Montgomery County. Ziparose. 
(Williams.) 
B. Binary granite, Guilford, Howard County. Toscanose. Con- 
tains quartz, orthoclase, a little plagioclase, muscovite, and biotite, 
with occasional zircon and apatite. (Keyes.) 
C. Biotite-granite, Woodstock. Toscanose. Light colored, line 
grained. Quartz, feldspar, and biotite, with accessory allanite and 
epidote. (Keyes.) 
D. Biotite-granite, Rowlandsville, Cecil County. Tonalose. Dark 
colored. Contains plagioclase, orthoclase, quartz, epidote, biotite, 
sphene, magnetite, and apatite, with a little secondary muscovite. 
The percentages of the several minerals are computed by Grimsley 
from the analysis. 
Analyses by W. F. Hillebrand, record Nos. 1220, 1422, 1455. In B 
and C manganese was present, barium and strontium were not tested 
for, and the alumina contains possible titanium and phosphoric acid. 
B. 
i). 
Si0 2 . 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 Oatl00°... 
H 2 above 100 c 
Ti0 2 
PA 
MnO 
SrO 
BaO 
Li 2 
74.87 
14.27 
trace 
.51 
.16 
.48 
3. 06 
5. 36 
.26 
.66 
.05 
.21 
trace 
trace 
72. 57 
15.11 
.59 
1.02 
.30 
1.65 
3.92 
4. 33 
.47 
undet. 
undet. 
undet. 
undet. 
undet. 
trace 
71.79 
15. 00 
.77 
1.12 
.51 
2.50 
3.09 
4.75 
}- .64 
undet. 
undet. 
undet. 
undet. 
undet. 
trace 
66. 68 
14.93 
1.58 
3.32 
2.19 
4.89 
2. 65 
2.05 
.16 
1.09 
.50 
.10 
.10 
trace 
.08 
trace 
99.89 
99. 96 100. 17 
100. 32 
