50 ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [no. 228. 
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. 
SB. 1 of Baltimoriase. Contains olivine, bronzite, and diallage, the 
olivine partly serpentinized. Analysis by T. M. Chatard, record No. 
1094. 
B. Pyroxenite, Johnn}^ Cake Road. Baltimorose. Consists entirely 
of hypersthene and diallage. P. R. C. 110. 
C. D. Alterations of B. Maricose. B, C, and D dried at 104°. 
E. Smaragdite rock, altered pyroxenite, Dogwood Road, Baltimore 
County. Oecilose. 
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. 
B. 
SiO,.. 
A1 2 3 . 
Fe 2 3 
FeO.. 
MgO . 
CaO.. 
Na^O. 
K,0.. 
H 2 OatllO° 
H 2 at red heat . 
TiO, 
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 
50.10 
2.00 
2.38 
8.68 
26.85 
5.06 
none 
4 16 
none 
none 
.36 
51.94 
2.53 
2.88 
9.38 
25.97 
3.60 
2.82 
none 
none 
.60 
.17 
trace 
.24 
.29 
trace 
.26 
trace 
.19 
.16 
100.03 
100. 14 
100. 07 
53.22 
3.14 
7.95 
20.09 
14.44 
> none > trace 
none 
.23 
.11 
trace 
.26 
100. 42 
