66 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
the olivine-free fine-grained diabases are greatly subordinate to the oli- 
vinitic diabases, ashbed-diabases and diabase-porphyrites among the fine- 
grained kinds, and to the non-orthoclastic and orthoclastic gabbros among 
the coarse-grained kinds. 
Tabulation of observations upon fine-grained olivine-free diabases of the “ordinary type.” 
Angle between 
maximum ex- 
tinctions of 
adjacent hemi- 
tropic bands of 
Ke the plagioclase 
3s Pla z Macroscopic char- | Constituents as determined by in sections cut 
| wah a} acters. microscope, in order of age. at random in 
5 , the zone O: it. 
A a & 
- & ;|/4 . Angles o: ‘OMe 
E 2 \2\8) & opposite | oS 
F a /S/—F) 8 sidesof | Sq 
BR Ce lala a cross-hair.| & © 
} ° ° ° 
Bed 22, Eagle |SWw./19/| 58 /31W.| Rather  fine- | Labradorite; augite,in part quite 34 
| River section, grained; indefi- fresh, in partaltered to a green 34 
Keweenaw nitely mottled pseudomorph. 36 
Point, Michi- dark green and 51 
gan; lowerzone.! purple. Sp, gr., 60 
2.77. 62 
Bed 22, Eagle |Sw.| 19} 58 |31W.| Like preceding, | Labradorite, all more or less al- 
River section, with numerous tered to prehnite, the change 
Keweenaw prehnite pseud- being at times complete; au- 
Point, Michi- amygdules, gite much altered; prehnite 
gan; pseud- averaging x5 to also forms countless pseud- 
amygdaloid linch apart, and amygdules from ‘microscopic 
zone.2 about ¥ inch in size up to 4 inch in diameter; 
: diameter. The also chlorite pseud-amygdules, 
prehnite is usu- and pseudomorphs after plag- 
ally of a flesh- ioclase. 
pink color, with 
or without vitre- 
ous luster, and 
is radiated or 
not. Sp.gr.,2.72, 
Bed 87, Eagle | NE.| 30} 58 /31W.) Rather fine- | Residuary base altered to dirty 22 
River, Kewee- grained; dirty white substances; apatite ? ; 23 
naw Point, gray-green; oligoclase much altered to 24 
Michigan; powder yields | pseudomorphs and pseud- 34 
lower zone. somemagnetite. | amyadules of chlorite; mag- a 
oe BEN 15 netite; augite highly fissured 
mee = and more or less thoroughly 
Composition: ; Ha eee i 
SiOz 46.32; AlsOs changed to chloritic sub- 
15.95: Fe203.86; stance, with which are asso- 
FeO 8.92; MnO ciated red and black iron 
.89; CuO 10.28; stains, which are probably 
MgO 4.08; Ti0z| the source of some of the 
2.78; KeO 1.23; magnetite. 
‘ Na2O 3.56; H20 
3.25 = 100.12. 
1Pumpelly, Metasomatic Development, p. 281. 2 Tbid., p. 282. ®Tbid., p. 283. 
