Tabulation of the results of a microscopic examination of augite-syenites, &c.—Continued. 
COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
| 
| 
| 
é | 
2 a Macroscopic char- 
3 Place. 2 | ; | acters. 
g seedy 
8 ON Baal xo 
3 a 1216] 2 
ra |@ lala] @ 
1067...| Eagle Mountain, labout| 23 | 68 |2W.| Fine-grained; 
Minnesota | highly crystal- 
(township not | line; brick-red; 
subdivided). | blotched with 
gray and black; 
appears to be 
chiefly made up 
of minute red 
feldspars. 
| 1520...) North shore of | SW./| 12 | 62 | 4E. | Brick-red; mi- 
Lake Superior, 7 nutely crystal- 
one mile above line; appears to 
the month of be made up of 
Maw-ske-quaw- minute red feld- 
caw-maw River. spars; crossed 
by parallel black 
stripes of rela- 
tively large size. 
Microscopic descriptions. 
Angle between 
maximum ex- 
tinctions of 
adjacent hemi- 
tropic bands of 
the plagioclase 
in sections cut 
at random in 
the zone O: ii. 
Argles on| o 
opposite se 
sides of| 23 
cross-hair. Be 
Resembles closely the last see- 
tion described, except that 
there are some coarser clus- 
ters of quartz which are 
plainly connected with that 
which saturates the feldspars. 
The latter attains, in this sec- 
tion, an extreme and most 
beautiful development. It 
often follows the cleavages in 
a most regular manner, and 
again forms groups of diverg- 
ing lines. The tendency seems 
to be for each quartz particle 
to have one narrow or even- 
pointed end, while the other 
is broad, club-shaped, or even 
hooked. The deposition of 
this secondary quartz has 
plainly been from without in- 
ward in each feldspar crys- 
tal. This is evidenced by its 
common greater abundance 
and coarseness in the outer 
portions of the crystals, some 
of the feldspar crystals being 
provided with a core, in which 
there is no quartz. This 
cors, when present, has linear 
outlines parallel to the sides 
of the original crystal. 
Allied to the last two described. 
It contains also long needle- 
shaped crystals of augite, 
largely altered to greenishand 
opaque ferritic substances ; 
numbers of these needles are 
parallel and appear to be parts 
of one original crystal. 
a teat 
