36 
ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. 
[bull. 
NEW YORK. 
I. ROCKS OF THE ADIRONDACK REGION. 
Collected by J. F. Kemp, who furnishes the petrographic data. A 
and G are described by Kemp in 19th Ann., Part III, p. 383. The 
other descriptions are hitherto unpublished. Analyses A and B by 
George Steiger, record No. 1715; C to G by W. F. Hillebrand, record 
No. 1717. 
A. Wall rock of iron mine near Lincoln Pond, Elizabeth town. 
Varies from norite to gabbro. Chief minerals, green augite, hyper- 
sthene, brown hornblende, plagioclase, and magnetite. Microperthitic 
feldspar less common. Garnet varies from absence to abundance. 
B. Coarse gabbro, top of Whiteface Mountain. A pyroxenic phase 
of the anorthosite. Contains much labradorite, abundant light-green 
augite, brown hornblende, shreds of more or less bleached brown 
biotite, and magnetite. 
Si0 2 
A1 2 3 
FeA 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 at 100° . . . 
H 2 above 100 c 
Ti0 2 
MO, CoO. 
MnO 
BaO 
C0 2 
s 
44.77 
12.46 
4.63 
12.99 
5.34 
10.20 
2.47 
.95 
.12 
.48 
5.26 
.28 
trace? 
.17 
trace? 
.37 
a. 26 
100. 75 
B. 
53.18 
23.25 
1.53 
1.82 
2.60 
11.18 
3.97 
.86 
.15 
.98 
.45 
.09 
(?) 
.11 
trace? 
.34 
trace 
100. 51 
a Mainly present as pyrrhotite. 
