38 PEGMATITES AND ASSOCIATED ROCKS OF MAINE.
temperature quartz. This pegmatite has been described by the writer in another report a and
is similar in most of its characteristics to the coarser Maine
deposits. The quartz of tins quarry is mostly white but is rose colored
in places. It is associated with the feldspar in a wholly irregular
maimer and forms large masses in one pit, being the principal rock on
two of the walls. These quartz masses at their borders are in intimate
intcrpenetration with the feldspar and may even grade into the quartz
of graphic granite. There is not the slightest doubt that they form an
integral part of the pegmatite mass, though very likely they were the
latest portion to crystallize.
Another
specimen of quartz, collected by the writer from the, pegmatite at an
old feldspar quarry on the northwest side of Mount Ararat in Topsham.
showed a quartz crystal about 1 .V inches across projecting with
perfectly developed pyramid faces into a crystal of pink microcline.
The crystal faces of the quartz were only shown when the feldspar was
broken away. The two minerals formed intimate parts of a large mass of
coarse pegmatite and plainly" crystallized contemporaneously. The
tests on this quartz (No. 20, W. and L.) indicate that it crystallized
below 575°.
Another
test (No. 16, W. and L.) was made upon quartz collected from the Berry
feldspar quarry in Poland, Me. The deposit is a gem-bearing pegmatite
and the quartz tested was irregularly inter-grown with rounded
lepidolite and bladed albite of the clevelandite variety. It occurred
in the solid pegmatite but near miarolitic cavities. The tests, though
not wholly conclusive, show that it probably belongs to the
low-temperature variety.
Crystals
of transparent smoky quartz (No. 15, W. and L.) developed on the walls
of pockets in the pegmatite at the same quarry exhibited
low-temperature characters. Similar results (No. 19, W. and L.) were
obtained for a compound quartz crystal developed in one of the pockets
at the G. I). Willes feldspar quarry in Topsham. At its proximate end
this crystal mass was intergrown witli the feldspar of the wall of the
pocket. It was plainly a pegmatite crystallization, though a late one.
A
specimen (No. 16, W. and L.), taken by the writer from a large mass of
white quartz several feet across in the pegmatite at the Fisher
feldspar quarry in Topsham, also showed the characters of the alpha or
low-temperature variety. These quartz areas form an intimate part of
the pegmatite mass, interlocking at their borders with crystals of the
other constituents and in places grading without break into the quartz
of coarse graphic granite.
In
contrast to the above tests on specimens of quartz from the large
quartz masses in the pegmatites and from the quartz in or near
a Bastin, E. S., Feldspar and quartz deposits of southeastern New York: Hull. I". S. Geol. Survey No. 315, 1907, pp. 395-398.
