66 ANALYSES OF ROCKS, U. S. GEOLOGICAL SURVEY. [bull. 168 
2. CRYSTAL FALLS DISTRICT, MICHIGAN. 
Rocks described by J. Morgan Clements and H. L. Smyth, 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. 41 N., R. 30 W. Contains quartz, orthoclase 
microcline, plagioclase, biotite, muscovite, magnetite, hematite, 'titan 
ite, 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 N., 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 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 OatllO°.... 
H 2 above 110° 
Ti0 2 
P 2 5 
MnO 
76.10 
12.95 
.65 
.09 
.14 
.12 
2.36 
6.50 
.17 
.48 
.07 
.02 
trace 
99.65 
74.37 
13.34 
.92 
.21 
.27 
.50 
2.50 
6.70 
.12 
.44 
.07 
.01 
trace 
99.45 
C. 
64.71 
16.43 
1.83 
3.84 
2.97 
.08 
.11 
5.63 
.31 
2.79 
.72 
.02 
trace 
99.44 
D. 
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. 
