42 ANALYSES OF KOCKS, U. S. GEOLOGICAL SURVEY. [bull. 168. 
MARYLAND, INCLUDING THE DISTRICT OF COLUMBIA. 
1. PERIDOTITE AND PYROXENITE. 
Rocks A to I, inclusive, described by G. H. Williams in Amer. 
Geologist, vol. 6, p. 35. 
A. Porphyritic lherzolite, Johnny Cake Road, Baltimore County. 
Contains olivine, bronzite, and diallage, the olivine partly serpentinized. 
Analysis by T. M. Chatard, record No. 1094. 
B. Pyroxenite, Johnny Cake Road. Consists entirely of hypersthene 
and diallage. P. R. C. 110. 
C. D. Alterations of B. B, C, and D dried at 104°. 
E. Smaragdite rock, altered pyroxenite, Dogwood Road, Baltimore 
County. 
Analyses B, C, D, and E by J. E. Whitfield, record Nos. 975, 976. 
C, D, and E are from the laboratory record, and do not appear in the 
published paper. 
SiO a . 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 OatllO° 
H 2 at red heat. 
Ti0 2 
PA 
Cr 2 3 
NiO 
MnO 
S0 3 
CI 
43.87 
1.64 
8.94 
2.60 
27.32 
6.29 
.50 
1.08 
7.64 
.12 
trace 
.44 
trace 
.19 
100. 63 
50. 80 
3.40 
1.39 
8.11 
22.77 
12.31 
trace 
.52 
none 
trace 
.32 
.17 
trace 
.24 
100. 03 
50.10 
2.00 
2.38 
8.68 
26.85 
5.06 
none 
4.16 
none 
none 
.36 
.29 
trace 
.26 
100. 14 
51.94 
2.53 
2.88 
9.38 
25.97 
3.60 
none 
2.82 
none 
none 
.60 
trace 
.19 
.16 
100. 07 
53.22 
3.14 
7.95 
20.09 
14.44 
trace 
.98 
.23 
.11 
trace 
.26 
100. 42 
