IGNEOUS AND CRYSTALLINE ROCKS. 33 
3. GRANITE AND GNEISS. 
For descriptions see Williams, 15th Ann., p. 657, and Keyes, idem, p. 685. The 
Rowlandsville granite is described by Grimsley in Jour. Cincinnati Soc. Nat. Hist., 
vol. 17, p. 78. 
A. White granite, Brookville, Montgomery County. Liparose. (Williams.) P. 
R. C., 1751. 
B. Binary granite, Guilford, Howard County. Toscanose. Contains quartz, ortho- 
clase, a little plagioclase, muscovite, and biotite, with occasional zircon and apatite. 
(Keyes.) * 
C. Biotite granite, Woodstock. Toscanose. Light colored, fine grained. Quartz, 
feldspar, and biotite, with accessory allanite and epidote. (Keyes.) 
D. Biotite granite, Rowlandsville, Cecil County. Tonalose. Dark colored. Con- 
tains plagioclase, orthoclase, quartz, epidote, biotite, sphene, magnetite, and apatite, 
with a little secondary muscovite. The percentages of the several minerals are com- 
puted 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. 
A B Cc D 
71.79 66. 68 
15. 00 14.93 
aohd 1.58 
1.12 3.32 
51 2.19 
2.50 4.89 
3.09 2.65 
4.75 2. a 
16 
-64) 109 
undet. 50 
undet. 10 
undet. 10 
undet. trace 
undet. -08 
trace trace 
100.17 | 100.32 
E. Biotite granite, Dorseys Run, Howard County. Yellowstonose. Typical, dark 
colored. Quartz, feldspar, and biotite, with accessory allanite and epidote. (Keyes.) 
P.R. C., 1752. 
F. Same locality, light-colored dikes. Toscanose. 
G. Inclusions in E. SR. 2 of tonalase. Derived from gneiss. 
H. The typical gneiss of the Dorseys Run area. Perhaps of sedimentary origin. 
Descriptions by Keyes. Analyses by Hillebrand. The remarks appertaining to 
B and C apply here also. Record No. 1220. 
