ORTHOCLASE-FREE GABBRO. 
47 
Tabulation of observations on coarse orthoclase-free gabbro and diabase—Continued. 
Specimen number. 
579... 
583.... 
587.... 
588... . 
658... 
Place. 
North shore Lake 
Superior; east 
point of Sucker 
RiverBay, Min- 
nesota. 
-| North shore Lake 
Superior, near 
east point of 
Sucker River 
Bay, Minnesota. 
North shore Lake 
Superior, _ be- 
tween Knifeand 
Sucker Rivers, 
Minnesota. 
North shore Lake 
Superior, _ be- 
tweenmouthsof 
Knife and Suck- 
er Rivers, Min- 
nesota. 
Encampment 
Bluff, north 
shore Lake Su- 
perior, Minne- 
sota, 
Encampment 
River, Minne- 
sota. 
Quarter-section. 
| Section. 
Township. 
Range. 
Macroscopic char- 
acters. 
n 
5 
SE. 
SE. 
SE. 
SE. 
36 
22 
10 
51 
51 
51 
51 
52 
12W. 
12W. 
12W. 
12W. 
12W. 
12W. 
10 W. 
10 W. 
Medium- grained ; 
light - gray; 
rough-textured. 
Medium-grained ; 
light-gray; 
rough-textured; 
close to 579. 
Medium-grained ; 
dark -gray; 
rough-textnred ; 
altered. 
Medium-grained ; 
light-gray; 
rough-textured ; 
near 579. SiO, 
46. 44 per cent. 
Medium- grained; 
light-gray; 
rough-textured; 
near 579. 
Medium- grained; 
dark-gray; 
rough-textured; 
near 579, 
Medium -grained ; 
dark-gray; 
rough-textured. 
Medium to coarse- 
grained; black ; 
rough-textured. 
Sp. gr., 2.89. 
Constituents as determined by 
microscope, in order of age. 
Angle between 
maximum ex- 
tinctions of 
adjacent hemi- 
tropic bands of 
the plagioclase 
in sections cut 
at random in 
the zone O: iz. 
Olivine, mostly very fresh, in 
part altered to a green sub- 
stance; anorthite; titaniferous 
magnetite; diallage, in large 
areas, including many feld- 
spars. A very fresh rock. 
Olivine, mostly very fresh, in 
part altered to a green sub- 
stance; anorthite; titanifer- 
ous magnetite; diallage, in 
large areas, including many 
feldspars. 
Olivine, very large and aban- 
dant, wholly altered toa green 
substance and magnetite ; an- 
orthite; titaniferous magne- 
tite; augite ; diallage. 
Olivine, mostly very fresh; an- 
orthite; titaniferous magne- 
tite; diallage in large areas. 
A very fresh rock. 
Olivine, very large, abundant 
and fresh; anorthite; titan- 
Yferous magnetite; diallage ; 
green alteration-products of 
olivine and diallage. 
Olivine, very large and abun- 
dant; anorthite; titaniferous 
magnetite ; augite, in part di- 
allagic; green alteration-pro- 
ducts of olivine and augite; 
brown iron oxide. 
Olivine ; labradorite ; titanifer- 
ous magnetite ; augite, in part 
diallagic, very coarse; serpen- 
tine as alteration-product of 
olivine; a@ green alteration- 
product of augite. 
Olivine, partly altered; anor- 
thite ; titaniferous magnetite ; 
augite non-diallagic; altera- 
tion-products of olivine and 
augite. 
Angles on | 2 
opposite | o% 
sidesof| 42 
cross-hair.| = @ 
| 
° ° 
20 21 41 
26 32 58 
36 36 72 
18 24 42 
42 30 72 
32 47 79 
33 31 64 
33 35 68 
31 30 61 
34 39 73 
35 40 75 
37 35 72 
33 37 70 
32 39 71 
37 43 80 
31 40 71 
38 38 71 
30 30 60 
27 33 60 
32 33 63 
24 26 50 
26 28 54 
25 27 52 
26 24 50 
24 23 47 
37 42 79 
27 37 64 
23 44 67 
37 33 70 
—— eS eee eee a a ee 
