ORTHOCLASE-FREE GABBRO. 
45 
Tabulation of observations on coarse orthoclase-free gabbro and diabase. 
Place. 
Specimen number. 
Bed 107, Eagle 
River section, 
Keweenaw Point. 
93 W .| Near Potato River, 
Ashland County, 
Wisconsin. 
1661..| Ashland County, 
Wisconsin. 
81661 | Ashland County, 
Wisconsin. 
2028 S.| Bad River, Ash- 
land County, Wis- 
consin. 
121...| Bad River, Ash- 
land County, 
Wisconsin. 
701...) Ashland County, 
Wisconsin. 
lS 
Section. 
Township. 
Macroscopic char- | 
acters. | 
SE. 
Nw. 
Nw. 
NE. | 31 | 45 | 2 W. 
Nw. 
45 | 1E. 
15 | 45 
34 | 45 
31 | 45 | 2 W. 
6 | 44/3 W. 
| 
Medium- grained; 
black -and-white- 
mottled. 
Mediom- grained; 
dark-gray ; rough- 
textured. Sp. gr., 
2.95. 
Coarse-grained; 
very light-colored, 
gray, mottled with 
much white; 
rough-textured. 
Sp. gr., 2.80. 
Fine-grained; 
dark-gray. 
Very coarse-grain- 
ed; _ light-gray; 
mostly made up of 
very coarse pla- 
gioclase, in which 
are embedded 
very numerous 
large olivines. 
Sp. gr., 2.82. 
Coarse-grained; 
dark-gray, some- 
what stained 
with brown; 
rough - textured. 
Sp. gr., 2.81. 
Very coarse-grain- 
ed; light gray; 
shows much 
olivine to naked 
eye. 
Constituents as determined by 
microscope, in order of age. 
Anorthite; magnetite, or titanic 
tron; augite. (Pumpelly.)! 
Anorthite ; augite tending to di- 
allage; alittle altered magma. 
(Pumpelly.)? 
Olivine, in large areas reaching 
2mm in length, largely quite 
fresh, but also in part altered 
to ochre, biotite and tale; an- 
orthite, greatly predominating ; 
diallage. 
Olivine, largely quite fresh; an- 
orthite abundant; titaniferous 
magnetite ; augite, only slightly 
diallagic. 
Olivine, very abundant and coarse, 
making up over one-third of the 
section, the particles elongated, 
reaching one-fourth inch in 
length, wholly altered to viri- 
dite, with some biotite in the 
interior and a shell of tale 
scales; anorthite; magnetite, 
sparse; augite ; diallage, sparse. 
Olivine, partly fresh, partly 
altered, reaching 1.3™™ in 
length; labradorite greatly 
predominating; augite; biotite 
in minute scales between the 
plagioclase grains; viridite, 
biotite and tale secondary to 
olivine ; viridite and magnetite 
secondary to augite; ochre.3 
Olivine, very abundant, and 
coarse, partly fresh, partly 
Angle between 
maximum ex- 
tinctions of 
adjacent hemi- 
tropic bands of 
the plagioclase 
in sections cut 
at random in 
the zone O; ii. 
altered to biotite and talc; 
labradorite or anorthite 
crowded with black needles, 
constituting most of the sec- 
tion; magnetite, sparse; 
augite, only slightly diallagic. 
Angles on| 2 
opposite | og 
sides of | 4 
cross-hair.) & a 
° ° ° 
=Asene| besos 49 
60 
70 
75 
28 31 59 
33 35 68 
32 29 61 
26 23 49 
23 34 67 
18 21 39 
31 30 61 
31 32 63 
34 30 64 
25 28 53 
37 38 75 
28 30 58 
19 18 37 
18 19 37 
32 33 65 
28 28 56 
18 21 39 
1Metasomatic Development of the Copper-bearing Rocks of Lake Superior, Proc. Am. Acad. Sci., Vol. XIII., pp. 256, 259. 
2Geology of Wisconsin, Vol. IU, p. 38. 
8 See also A. A. Julien, Vol. Il, Geology of Wisconsin, pp. 235 to 237. 
