46 THE GRANITES OF MAINE. 
at the Settlement quarry, near Stonington (see p. 108), the coarse 
granite is traversed by a dike, from 4 to 12 inches thick, of light 
pinkish-gray granite, in which the feldspars attain a size of one- 
tenth of an inch (2.5 mm.), but under the microscope some are found 
that measure as little as 0.025 inch (0.12 mm.). This rock consists of 
a pinkish potash feldspar (microcline), a white soda-lime feldspar 
(oligoclase-andesine), smoky quartz, and black mica (biotite). At 
the Mosquito Mountain quarry (p. 153), near Frankfort, there is a 
10-foot dike of medium-grained gray granite (quartz monzonite), 
with feldspars up to 0.3 inch. The potash feldspar (microcline) is 
about equal in amount to the soda-lime feldspar (oligoclase), the 
quartz is smoky, and the mica is black. At the Mount Waldo quarry 
(p. 155) there is a dike 200 feet wide of fine biotite granite, with 
coarse biotite granite on both sides of it. The feldspars of this dike 
measure up to 0.15 inch, but range ordinarily from 0.30 to 1.45 mm. 
The fine-grained biotite-muscovite granites quarried at the Sherwood 
quarry, on Crotch Island (spec. 25, a, described on p. 105), at East 
Bluehill (spec. 39, c/, on p. 87), and at a small opening on Dodlin 
Hill, near Xorridgewock (spec. 117, a, described on p. 152), all seem 
to belong to similar dikes that are not many feet in thickness. At 
an old quarry near Bluehill (p. 85) there is an 18-inch dike of fine- 
grained muscovite-biotite granite, in which the feldspars are much 
intergrown with quartz. The courses of these granite veins are N., 
N. 15° E., N. 20° W., N. 55° E., N. 70° W. All such dikes represent 
granitic intrusions. 
VEINS. 
Quartz yeins are exceptional in the Maine quarries. At the old 
Bodwell Company's quarry on Cook's Mountain, near Redbeach, now 
abandoned, the red granite is traversed by a banded grayish quartz 
vein, about 18 inches thick, that has a course N. 25° W. and a vertical 
dip. It comprises three, or. in places, four bands, which differ 
mainly in texture and are separated by more or less pyrite in fine 
particles. In places this vein divides into three smaller veins, each of 
which is from 3 to 4 inches thick. The quartz contains some purple 
fluorite (lime fluoride), as determined by W. T. Schaller at the 
chemical laboratory of 'the United States Geological Survey, and a 
variable amount of a foliaceous lemon-colored mineral which Wirt 
Tassin, of the United States National Museum, has analyzed and 
determined as a new variety of sericite, resulting, possibly, from 
the alteration of a feldspar, and which is accompanied by another 
mineral, regarded by him as probably talc. Mr. Tassin's analysis and 
report are as follows: 
