and
mica crystals 8 to 10 inches in diameter. The arrangement and position
of the different minerals in the pegmatite is very irregular.
The
quartz of the pegmatite is white, gray, or smoky, mostly opaque, but
some is translucent and nearly clear. The muscovite is clear
rum-colored and part has a good cleavage. Biotite is plentiful; some of
it is intergrown with the muscovite. Black tourmaline is present in
some places in crystals up to 2J inches thick. Opaque dull-red garnet
crystals half an inch to 2 inches in diameter are scattered through
the pegmatite, and a few small pink garnets were observed in one
specimen on the dump. Only a few beryl crystals were seen in the rock.
These were yellowish green to pale aquamarine-green and mostly opaque.
Little could be learned of the quality of the gem material found during
mining.
New
prospects for mica and beryl were opened during 1914 by Charles Murphy,
of Wilmot, on the old Underbill place, about If miles N. 75° E. of
Springfield in Sullivan County. Only one of these was of interest for
its possible gem minerals. This consisted of an open cut 20 feet square
and 12 feet deep in a large pegmatite outcrop. Much of the rock exposed
in the working is graphic granite of both coarse and fine grain. In
places there are small segregations of quartz and orthoclase crystals
measuring from a few inches to 1 foot thick. About 4 tons of small mica
crystals suitable for cutting into small sheets and for punching were
taken from this opening. A great many beryl crystals were found. These
range from one-sixteenth of an inch to \\ inches in diameter.
They are well-formed simple hexagonal prisims occurring separately in
parallel growths, and in radialg roups. Most of them are opaque or only
translucent and have pale-greenish aquamarine color. Up to the time of
examination no beryl of gem quality had been found. Among associated
minerals are biotite, black tourmaline, opaque red garnet up to 2
inches in diameter, triphyllite in masses up to 8 inches thick,
loflingite or arsenopyrite, and apatite.
PENNSYLVANIA.
Beryl
crystals occur at many localities in Chester and Delaware counties,
Pa., and occasionally one of sufficiently good color and quality for
cutting into gems is found. Many of the crystals are obtained from the
pegmatite deposits worked, for feldspar, but a few have been found in
small veins or deposits or pegmatite inclosed in other rocks. One of
the best-known localities of this type is in the C. F. Leiper quarry at
Avondale, Delaware County. This quarry has been opened by a cut nearly
a quarter of a mile long in a north and south direction, 100 to 250
feet wide and 40 to 80 feet deep. The rock quarried is a
muscovite-biotite granite gneiss, strongly schistose in some phases. A
few streaks or veins of quartz and pegmatite are inclosed
approximately conformably with the gneiss, that is, striking north and
south with nearly vertical dip. The pegmatite veins examined vary from
1 inch to 2 feet in thickness, pinching and swelling along the strike.
They contain flesh-colored potash feldspar, opaque brownish-red garnet
up to 2-1/2 inches in diameter, black tourmaline, masses of gray quartz, and muscovite up to 1-1/2 inches
in diameter. Fragments of golden beryl crystals were observed at two
places in one of these pegmatite veins, but the better
