292 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[BULL. 168. 
VIRGINIA, NORTH CAROLINA. 
A. Residual clay from decay of Trenton limestone, Lexington, Vir- 
ginia. Described by Russell in Bull. 52. Analysis by R. B. Riggs, 
record No. 373. See also analysis of the limestone. 
B. Residual clay from limestone, Staunton, Virginia. 
C. Portion of B soluble in weak hydrochloric acid. 
D. Insoluble portion of B. Analyses B, C, and D by George 
Steiger, record No. 1630. See also analysis of limestone. 
E. Decomposed dolerite, near Wadesboro, North Carolina. De- 
scribed by Russell in Bull. 52. Analysis by T. M. Chatard, record 
No. 327. 
F. Residual clay from decay of chloritic schist, Cary, 8 miles west 
of Raleigh, North Carolina. Analysis by R. B. Riggs, record No. 364. 
Described by Russell in Bull. 52. 
A. 
B. 
c. 
D. 
E. 
F. 
SiO, 
43.07 
25.07 
15.16 
55.90 
19.92 
7.30 
.39 
1.18 
.50 
.23 
4.79 
2.54 
6.52 
.20 
.10 
3.09 
3.96 
6.25 
.30 
.43 
.30 
.20 
.28 
52.81 
15.96 
1.05 
.09 
.75 
.20 
.03 
4.51 
39.55 
28.76 
16.80 
54. 54 
26.43 
9.04 
ALO, 
Fe 2 3 
FeO 
MgO 
.03 
.63 
1.20 
2.50 
| 12.98 
.59 
.37 
undet. 
undet. 
1 13.26 
.64 
.10 
trace 
trace 
CaO 
Na 2 
K 2 
H 2 Oatll0 o ._. 
H 2 above 110° 
Ti0 2 
} 9.87 
2.10 
.04 
.04 
4.42 
.16 
.06 
P 2 5 
O 2 3 
MnO 
none 
.38 
co 2 . . 
.38 
none 
100. 64 
99.95 
17.37 
80.04 
100. 07 
99.88 
