78 
ANALYSES OF KOCKS, U. S. GEOLOGICAL SURVEY. 
[NO. 228. 
2. CRYSTAL FALLS DISTRICT, MICHIGAN. 
Rocks described by J. Morgan Clements and H. L. Sm} T th, in Mon. 
XXXVI. A, B, C, and D by Smyth, p. 274. Analyses by H. N. 
Stokes, record No. 1721. 
A. Granite, sec. 2, T. 11 N., R. 30 W. Magdeburgose, Contains 
quartz, orthoclase, microcline, plagioelaye, biotite, muscovite, magnet- 
ite, hematite, titanite, and occasional apatite. 
B. Gneiss, sec. 35, T. 42 N., R. 29 W. Same minerals as in A. 
C. Mica-schist, sec. 35, T. 42 K, R. 29 W. Contains biotite, quartz, 
some microcline, and magnetite. 
D. Amphibolite, sec. 32, T. 42 N., R. 28 W. Contains hornblende, 
plagioclase, biotite, and quartz, with a little rutile and magnetite. 
Si0 2 
A1A 
Fe 2 0, 
FeO 
MgO 
CaO 
K 2 
H 2 OatllO°..._ 
H 2 above 110° 
Ti0 2 
P 2 5 
MnO 
A. 
B. 
C 
76. 10 
74.37 
64.71 
12. 95 
13.34 
16.43 
.65 
.92 
1.83 
.09 
.21 
3.84 
.14 
.27 
2.97 
.12 
.50 
.08 
2.36 
2.50 
.11 
6.50 
6.70 
5.63 
.17 
.12 
.31 
.48 
.44 
2.79 
.07 
.07 
.72 
.02 
.01 
.02 
trace 
trace 
trace 
99.65 
99.45 
99.44 
50.36 
13.26 
6.30 
9.34 
5.55 
7.85 
2.11 
1.14 
.16 
1.55 
1.77 
.20 
trace 
99.59 
Ba, Sr, CI, F, S, S0 3 not looked for. 
