CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
47 
E. Biotite-granite, Dorseys Run, Howard County. Typical, dark 
colored. Quartz, feldspar, and biotite, with accessory allanite and 
epidote. (Keyes.) 
F. Same locality, light-colored dikes. 
G. Inclusions in E. Derived from gneiss. 
H. The typical gneiss of the Dorseys Run area. Perhaps of sedi- 
mentary origin. 
Descriptions by Keyes. Analyses by Hillebrand. The remarks 
appertaining to B and C apply here also. Record No. 1220. 
Si0 2 . 
A1A 
Fe 2 3 
FeO. 
MgO 
CaO. 
Na 2 
K 2 0. 
H 2 0. 
Li 2 
62.91 
19. 13 
.98 
3.20 
1.69 
4.28 
3.94 
3.38 
.63 
trace 
100. 14 
70.45 
15.98 
.75 
1.84 
,77 
2.60 
3.83 
3.59 
.45 
trace 
100. 26 
G. 
57.33 
15. 31 
3. 39 
8.19 
4.36 
3.95 
1.22 
4.57 
1.80 
trace 
100. 12 
ii. 
48.92 
16.57 
4.21 
9.18 
5.98 
9.69 
2.47 
1.56 
1.68 
trace 
100. 26 
I. Biotite-granite, Sykesville. Contains quartz, feldspar, and bio- 
tite, with accessory magnetite, zircon, and apatite. 
J. Inclusion in I, derived from limestone. Yellowish central portion. 
Consists of epidote and quartz, with a little chlorite. 
K. Same inclusion, fine-grained dark outer zone. Quartz, garnet, 
and epidote, with a little magnetite. Feldspar and muscovite in some 
portions. Descriptions by Keyes. Analyses by Hillebrand, record 
No. 1220, with the same limitations as in the Guilford, Woodstock, and 
Dorseys Run granites. 
I. 
J. 
K. 
Si0 2 
71.45 
14.36 
2.07 
2.78 
1.17 
1.58 
1.95 
3.28 
1.30 
trace 
67.02 
13.77 
4.64 
1.02 
.65 
11.09 
.66 
.09 
1.16 
trace 
47. 3§ 
29.76 
2.94 
3.15 
1.60 
2.20 
2.84 
6.83 
3.15 
trace 
A1 2 3 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 .' 
Li 2 
99.94 
100. 10 
99.82 
