170 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
coarser varieties of Vinalhaven and that of Hurricane Island, for which 
it might readily be mistaken. It however differs microscopically in 
containing muscovite, garnet, and epidote, and no hornblende, as do 
both of these rocks. 
Two varieties of granite are quarried at Mount Waldo, in the town of 
Frankfort. Both are light-gray rocks, frequently porphyritic through 
large white orthoclase crystals. Both varieties are of the same min- — 
eral composition, the difference being simply one of texture, one being 
quite coarse and somewhat porphyritic, while the other is much finer 
and of more even texture. As would naturally be expected, the finer 
grade is the better and more durable rock, the coarser variety being 
more liable to crumble. The mica occurs in large flakes, which the mi- 
eroscope shows to be frequently pierced by small crystals of apatite. 
A part of the mica is greenish in color and contains a few small faintly 
pleochroic grains of epidote. An occasional flake of white mica was 
noticed in this rock, and there is present the usual sprinkling of mag- 
netite granules, together with an occasional cube of pyrite. Quarries 
were opened at Mount Waldo in 1853, and single blocks 80 by 40 by 20 
feet have been taken out and afterward cut up. It is estimated that 
blocks 150 by 50 by 12 feet could be obtained if desired. The rock has 
been used largely in the building of: forts on the coast of Maine, but is 
also used for all purposes, both ornamental and otherwise, to which 
granite is usually applied. It is a beautiful stone when polished. 
The granites from the numerous quarries about Vinalhaven all have 
biotite as the characterizing accessory, though in many of them more 
or less hornblende is present.* They vary in texture from very fine to 
coarse, and are mostly dark gray in color, though the coarser varieties 
are sometimes of a pinkish tinge, owing to the presence of a flesh- 
colored orthoclase. In thin sections the feldspar of this rock is seen 
to be nearly all orthoclase, but little plagioclase being present. The 
microscope brings to light small apatite, magnetite, and zircon crystals, 
invisible to the unaided eye. These are all compact, safe working stones, 
and take a good polish. They are extensively used both for building 
and ornamental purposes in all the leading cities throughout New En- 
gland and the West. Quarries were first opened at Vinalhaven about 
the year 1850. The largest single block ever taken out was the obelisk 
for the General Wool monument at Troy, N. Y., which measured when 
dressed 60 by 54 by 54 feet. It is stated that at the “Harbor Quarry” 
a single block 240 feet long by 32 feet wide and 8 feet in thickness — 
might be obtained if desired. 
The rock of Hurricane Island closely corresponds to that of Vinal- 
*In Hitchcock’s ‘‘ Report on the Geology and Natural History of Maine,” 1862, p. 
265, the Vinalhaven rock is referred to as a “ peculiarly fine-grained syenite of good 
color,” &c. In none of the specimens received at the Museum from this locality, 
however, does hornblende play more than a secondary part, and in the majority of 
cases does not appear at all. Hence, all are classed as biotite granites. 
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