54 
COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
Tabulation of observations on orthoclase-bearing gabbros—Continued. 
Angle between 
maximum ex- 
tinctions of 
adjacent hemi- 
tropic bands of 
5 A : : a the plagioclase 
| Place. g Macroscopic char- Constituents as determined by in sections cut 
5 3 acters. microscope, in order of age. at random in 
| S : the zone O: zi. 
g 4 | # ; Angles on | 2 
4 = & é &p apiorite cet 
2 Sie lboaleaal eas sides of | 43 
a e l|alal| & crosshair.) © 
° ° ° 
61. | Cut on Wiscon- | SE. | 30 | 45 | 2W.| Coarse-grained; | Oligoclase, predominating in| 14 16 30 
sin Central red - and - black large crystals, much clouded, 9 10 19 
Railroad, Bad mottled ; rough- but still showing the banding | 14 14 28 
River, Ashland textured. distinctly; orthoclase; very 
County, Wis- coarse titanic magnetite ; 
consia. greenish hornblende or uralite, 
showing strong dichroism, 
and in a marked degree the 
characteristic prismatic cleav- 
age, but evidently an altera- 
tion from diallage and augite, 
as proved by the existence of 
a few cores of the original 
substance. This hornblendio 
mineral fills in the spaces be- 
tween the oligoclases in the 
manner characteristic of the 
gabbros. 
641. | Brunschweiler’s | SE. | 16 | 45|4 W.| Coarse-grain‘ed, | Apatite, in very large crystals; | 21 | 23 | 44 
River, Ashland dark greenish- labradorite ; orthoclase; titan- | 16 22 38 
County, Wis- gray, mottled iferous magnetite, very abun- 
consin, with dull red| dant and coarse; wralite; 
and white. quartz, ferrite, secondary feld- 
spars; chlorite, secondary to 
uralite. 
1121. | Bayfield County, | NE.| 12 | 44 | 6 W.| Coarse-grained; | Oligoclase; orthoclase; highly | 10 14 24 
Wisconsin. dark greenish-| altered titaniferous magnetite, 
gray, sparsely very coarse and abundant; di- 
mottled with] allage, almost wholly altered 
red; dull. to uralite ; chlorite secondary 
to feldspars ; ferrite. 
2021. | Douglas County, | SE. | 32 | 48 |12 W.| Medium-grained; | Apatite in long crystals; oligo- | 10 il 21 
Wisconsin. red- and - gray - clase, stained red; orthoclase; | 17 15 32 
mottled. Sp. diallage, sparse, mostly al-| 10 ll 21 
gr., 2.76. tered to a dark-green sub- 
stance; ferrite, chlorite, 
quartz, secondary to feldspars. 
2051. | Aminicon River, | SE- | 32 | 48 |12W.| Coarse-grained. | Labradorite (in sections cut at 
Douglas County, 
Wisconsin. 
red-and black- 
mottled. 
random in the zone O: 72, the 
angle ranged from 37° to 509; 
a section cut independently 
and carefully parallel to O 
gave 12° to 14°); orthoclase ; 
augite; diallage in twinned 
plates. (Pumpelly, Geology of 
Wisconsin, Vol. III., p. 41.) 
