CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
61 
VIRGINIA. 
A. Andesite, Si miles east of Front Royal. SB. 4 <>f orendase. 
Described by Keith in 14th Ann., p. 305. Intermediate between dia- 
base and quartz-porphyry. Contains plagioclase, quartz, magnetite, 
ilmenite, and a little epidote. Analysis by George Steiger, record 
No. 1450. 
B. Porphyritic felsite or felsophyre, forks of Straight Creek, 3 miles 
ENE. of Monterey. Toscanose. Described by Dartonand Keith in Am. 
Journ. Sci., 1th series, vol. 6, p. 305. Contains phenocrysts of biotite, 
orthoclase, and plagioclase, the mica and feldspar being about equal in 
amount. In the groundmass are feldspar, quartz, magnetite, or ilmen- 
ite, and a little secondary chlorite with less muscovite. No glass. 
Analysis by Hillebrand, record No. 1665. P. R, C. 342. 
B. 
Si0 2 
A1A 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 Oatll0°.... 
H 2 above 110° 
Ti0 2 
PA 
MnO 
SrO 
BaO 
Li 2 
C0 2 
Cl.F 
51.08 
1 1 . 37 
11.17 
5. 64 
3.96 
5. 20 
5. 54 
1.50 
1.31 
.19 
2.67 
. 39 
.22 
69.56 
15. 52 
1.67 
1.19 
.41 
1.20 
4. 46 
4.68 
.34 
.67 
.31 
.08 
.07 
trace 
.10 
trace 
none 
(?) ' 
trace 
100.24 
100.26 
