A
third small pit, 40 by 40 feet and 8 feet in average depth, just north
of the one described, shows some feldspar of commercial grade, as does
also a small prospect pit on the southeastern slope of the hill. In the
unopened natural exposures near these quarries practically all the rock
is too fine grained or too rich in muscovite or iron-bearing minerals
to be valuable for pottery purposes. As far, therefore, as can be
judged from the present exposures these quarries show little prospect
of yielding much feldspar of pottery grade. The material may ultimately
prove of value for poultry grit, fertilizer, or other uses where
iron-bearing minerals are not detrimental.
The
pegmatite of these quarries, though of poorer quality commercially
than that at the quarries of the Maine Feldspar Company, appears to
form a part of the same large pegmatite mass. The excavating has been
in part by hand drilling and blasting and in part by steam drilling.
The equipment includes a small derrick.
Towne feldspar and gem quarry.—In
April, 1907, a quarry was opened by J. S. Towne, of Brunswick, Me., on
the Pulsifer farm about one-half mile northwest of the Maine Feldspar
Company's quarries on Mount Apatite. This quarry is operated by the
Maine Feldspar Company for feldspar, the gems found being handled by
Mr. Towne.
The
workings were visited by the writer in October, 1907, at which time
they consisted of three very small pits all on the same half acre. All
are in pegmatite but only two expose the pockety or gem-bearing zone.
The third pit is higher on the hill slope, and has not yet got down to
the pocket-bearing layer; in the lower pits it has penetrated it for 4
feet but has not yet reached its base. The gem-bearing layer, though
grading gradually into the other pegmatite, is distinguishable from it
not only by the presence of pockets but by being somewhat coarser than
other portions of the pegmatite. It is characterized by the presence of
clevelandite, lepidolite, and green tourmaline embedded in the solid
pegmatite, the usual "indicators" of proximity to gem tourmalines. The
pocket-bearing layer appears to dip about 10° E. The bordering schists
are not exposed in the vicinity of this quarry.
The
feldspar obtained from these pits is similar to that mined at the Maine
Feldspar Company's quarry, and of equal value. Black tourmaline is
abundant near many of the pockets, as is also green tourmaline in
semitransparent crystals up to one-eighth inch in diameter, penetrating
or interleaved with muscovite. As at most localities where gem
tourmalines are found, biotite is almost entirely absent. Garnets are
not abundant in the pocket-bearing layer, though fairly abundant in the
bordering phases of the pegmatite. Lepidolite occurs both in granular
aggregates of small scales and prisms and in large curved crystals with
rounded botryoidal surfaces one-half inch
