46 
ANALYSES OF KOCKS, U. S. GEOLOGICAL SURVEY. 
[LULL. 168. 
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. (Williams.) 
B. Binary granite, Guilford, Howard County. Contains quartz, 
orthoclase, a little plagioclase, muscovite, and biotite, with occasional 
zircon and apatite. (Keyes.) 
C. Biotite-granite, Woodstock. Light colored, fine grained. Quartz, 
feldspar, and biotite, with accessory allanite and epidote. (Keyes.) 
D. Biotite-granite, Rowlandsville, Cecil County. Dark colored. 
Contains plagioclase, orthoclase, quartz, epidote, biotite, sphene, mag- 
netite, 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. 
Si0 2 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 Oatl00°.... 
H 2 above 100° 
TiO, 
MnO 
SrO. 
BaO. 
A. 
74.87 
14.27 
trace 
.51 
.16 
.48 
3.06 
5.36 
.26 
.66 
.05 
.21 
trace 
trace 
99.89 
B. 
72.57 
15.11 
.59 
1.02 
.30 
1.65 
3.92 
4.33 
.47 
undet. 
undet. 
undet. 
undet. 
undet. 
trace 
99.96 
71.79 
15.00 
.77 
1.12 
.51 
2.50 
3.09 
4.75 
.64 
undet. 
undet. 
undet. 
undet. 
undet. 
trace 
100. 17 
14.93 
1.58 
3.32 
2.19 
4.89 
2.65 
2.05 
.16 
1.09 
.50 
.10 
.10 
trace 
.08 
trace 
100. 32 
