| Specimen number. 
1781d.| Pebble from Al- 8 55 |33 W. 
bany and Bos- 
ton conglomer- 
ate, Keweenaw 
Point, Michigan. 
NW. 
602...| Duluth, Minn. 
From red vein 12 
inches wide cut- 
ting coarse gab- 
bro, Rice Point 
quarry. 
Area of red rock 
in coarse gabbro, 
Duluth, Minn. 
Macroscopic char- 
acters. 
Fine-grained; 
highly crystal- 
line; dark brick- 
red; appears to 
be entirely made 
up of minute red 
feldspars. 
NW.| 34 50 |14W.) Flesh-red; highly 
crystalline; me- 
dium - grained; 
nate. 
Nw.| 27 50 |14W.)| Highly crystal- 
line; medium- 
Appears to have been originally 
pinkish feldspar 
facets predomi- 
grained; red, 
mottled with 
green. 
AUGITE-SYENITE AND GRANITELL. 
Microscopic descriptions. 
and fine frequently polarize 
together in large clusters. It 
also appears evident in this 
section that the fine radially 
arranged quartz affects, in 
part at least, original crystals. 
chiefly made of feldspar crys- 
tals, in part triclinic, with 
possibly also some finer ma- 
trix material. The crystals 
are now, however, all much 
dulled and altered, and more 
or less blotched with iron 
oxide. Inmany crystalslong, 
brownish ferrite lines follow 
the cleavage directions. An 
excessively fine secondary 
quartz fills some of the feld- 
spars, corners between which 
are sometimes occupied by 
coarser particles of quartz; 
but large parts of the section 
are singularly free from the 
usual quartz saturation. 
Clusters of opaque black and 
brownish particles, with now 
and then a brightly polarizing 
core, represent augites. 
Appears to have been originally 
made up entirely of feldspar 
crystals; but these are now 
completely saturated with 
secondary quartz in unusually 
coarse particles, arranged in 
a graphic form. See Figs. 3 
and 4, Plate XIV. 
A granite-like rock, in which 
the chief ingredients are red- 
dened feldspars and quartz. 
The quartz is in relatively 
large areas, filling spaces be- 
tween the feldspars; but in 
the neighborhood of the larger 
areas,saturating the feldspars, 
119 
Tabulation of the results of a microscopic examination of augite-syenites, ‘&c.—Continued. 
Angle between 
maximum ex- 
tinctions of 
adjacent hemi- 
tropic bands of | 
the plagioclase 
in sections cut 
at random in 
the zone O: it. 
opposite| o< 
ten cs) = 
cross-hair.| = 
° ° ° 
5 7 12 
4 6 10 
