CLARKE.] 
IGNEOUS AND CRYSTALLINE ROCKS. 
73 
4. PENOKEE-GOGEBIC REGION. 
Rocks mostly described by Van Hise in Mon. XIX. Analyses A to G 
by T. M. Chatard, record Nos. 991, 992, 993, 994, 905. 
A. Diabase, near SE. corner of sec. 13, T. 47 K, R. 46 W., Michi- 
gan. Contains plagioclase, augite, magnetite, apatite, and olivine, with 
some ilmenite and leucoxene. P. R. C. 1001. 
B. Same dike as A, partly altered. The pyroxene is altered to 
amphibole, and the latter partly to biotite. Biotite has also been 
derived from feldspar. P. R. C. 1000. 
C. Feldspar separated from A. 
D. Altered diabase, Aurora mine, NE. i of SW. i of sec. 23, T. 47 
N., R. 47 W., Michigan. P. R. C. 1002. 
Si0 2 
A1A 
Fe 2 3 
FeO 
MgO 
CaO 
Na 2 
K 2 
H 2 Oatl05°.... 
H 2 above 105° 
Ti0 2 
r 2 o 5 
Cr 2 3 
MnO 
NiO 
BaO 
CO, 
A. 
47.90 
15. 60 
3.69 
8.41 
8.11 
9.99 
2.05 
.23 
.15 
2.34 
.82 
.13 
trace 
.17 
.10 
.05 
.38 
100. 12 
46.85 
22.62 
5.12 
1.58 
2.01 
1.25 
.80 
2.66 
3. 12 
8.25 
1.12 
.16 
2.54 
.08 
.10 
1.89 
100.15 
51.18 
27.00 
3.19 
undet. 
1.92. 
11.70 
3.48 
.41 
1.19 
.17 
100. 24 
41.60 
37.20 
3.21 
.30 
.02 
.23 
.07 
.29 
13. 54 
3.79 
.14 
.08 
trace 
.38 
100. 85 
