of
green, bluish-green, and greenish-blue transparent crystals. Mr. Ware
has called some of the more beautiful green and bluish-green gems from
his mine emeralite, in allusion to their resemblance to emerald. Among
other mines the Esmeralda, 1£ miles north of Mesa Grande, was worked a
short time and yielded a few gem tourmaline and good pink beryl
crystals. This mine has never been a large producer, but good gems and
specimens of aquamarine and
p
ink beryl, along with varicolored tourmalines, have been taken from it.
CONNECTICUT.
Tourmaline
of value both as gems and specimens has been found at several places in
Middlesex County, Conn. Many of the specimens have been obtained from
quarries operated for feldspar for pottery, but in a few quarries the
mining has been for tourmaline and associated specimen minerals only.
A few of the quarries were visited in October, 1914, and are described
below.
The
M. P. Gillette feldspar quarry, known as the Haddam Neck quarry, is 1
mile N. 22° E. of Haddam, near tho east bank of Connecticut River. It
is one of the oldest quarries in Connecticut and, besides many gem
tourmalines, has yielded a number of fine specimens of other minerals.
The deposit has not been worked for several years and the pits were
partly filled with water and overgrown with vegetation at the time of
examination. Notes taken at that time have been supplemented from E. S.
Bastin's description.1 Tho quarry consists of one large
irregularly shaped open cut about 100 yards long in a north and south
direction and 100 feet wide iu the widest part, which joins a smaller
open cut on the west about 75 feet long m a north and south direction
and 35 feet wide. These quarries range from 20 to 30 feet deep and have
crosscuts leading out to two large dumps on the river side. One cut
extends west from the west quarry and the other west from the south end
of the east quarry. According to Bastin, the west quarry was worked
chiefly for tourmalines and specimen minerals. The east quarry was
worked chiefly for feldspar, also yielding some mica, gem tourmalines,
and specimen minerals.
The
country rock is dark-gray muscovite-biotite schist or gneiss, which
strikes about north with a vertical dip. Tho pegmatite is large and has
been split into several streaks by large inclusions or horses of
schist. In the north end of the quarries there are three beds of
pegmatite with a total thickness of about 100 feet in a width of 150
feet. In the middle of the quarry on the south side the schist
unconformably overlies a rounded boss of pegmatite. This boss pitches
to the south and on the north side of the quarry outcrops as a bed
nearly 50 feet thick conformably between schist walls. The pegmatite
contains large masses of graphic granite, potash feldspar crystals 1 to
3 feet across, generally with a little intermixed albite, albite,
muscovite, black and green tourmaline, and pockets or cavities lined
with crystals. Some of the mica crystals measure over 1 foot across and
are 6 inches thick, but do not split well because of the presence of
"wedge" and "A" structures.
Bastin describes the gem pockets in the east cut as averaging—
8
or 10 inches in diameter, though there are many smaller ones only 2 to
3 inches across. They are distributed with great irregularity through
ths pegmatite mass.
1 Feldspar deposits of the United States: U. S. Geol. Survey Bull. 420, pp. 4S-49,1910.
