crest
of this mountain trends in a northwest-southeast direction and was
examined for over half a mile of its length. The width of outcrop
examined from southwest to northeast across the trend of the ridge was
also about half a mile. The whole area traversed and the remainder of
the mountain so far as it could be seen was underlain almost
exclusively by coarse pegmatite, the mountain being essentially a
"boss" of this material. Near the highest part a few patches of schist
a few square yards in surface are entirely surrounded by pegmatite.
Another schist mass was 40 to 50 feet wide and 100 feet long. It was
bordered on three sides by pegmatite, its fourth contact being obscured
by vegetation. These masses appear to be entirely unconnected with any
large schist areas.
The
pegmatite is of the usual type, being an association, often in graphic
intergrowth, of quartz, orthoclase-microchne, muscovite, black
tourmaline, and subordinate amounts of biotite. In a few places, as on
the highest part of the mountain, it is coarse enough to yield feldspar
of suitable quality for pottery purposes, some masses of pure potash
feldspar being 2 to 3 feet across and rather coarse graphic granite
being abundant. Its inaccessible location would, however, render its
working impracticable under present conditions. Certain portions of
this pegmatite consist almost wholly of graphic granite, intersected by
blades of muscovite, but these areas grade into others characterized by
a granular-pegmatitic texture and containing the same minerals, but
also much black tourmaline and some garnet.
It
is difficult to conceive of a mass of this size and general uniformity
crystallizing under anything like vein conditions. With high gaseous
content and hence high mobility it would be natural to expect more
differentiation both in texture and composition. Although the
composition of the pegmatite magma was probably slightly different from
the normal granite magma, it seems probable that the rigidity of the
mass was not greatly less than that which would characterize a granite
boss of similar dimensions.
Mills feldspar quarry.—A
small abandoned feldspar quarry, situated on Number Four Hill, near
the Paris-Hebron line, was visited by the writer in August, 1906. The
quarry was worked by the Mount Marie Mining Company in 1901 but was
soon abandoned.
The
principal pit is about 75 feet long by 30 feet wide and 10 feet in
maximum depth. A second pit close by is about 30 by 30 feet and 10 feet
deep.
The
bulk of the feldspar belongs to the potash varieties, orthoclase, and
microcline, though some albite of the clevelandite variety occurs in
the coarser-grained portions. In the northwestern part of the larger
pit some masses of pure spar are 3 to 4 feet across. The bare ledge to
the north of the smaller pit for a length of 40 or 50 feet and a width
of about 30 feet shows feldspar in crystals 2 to 4 feet across
