Lepidolite
in finely granular masses, pale-green albite, and small green
tourmalines are abundant near many of the pockets. Muscovite surrounded
by a border of lepidolite, or in parallel growth with lepidolite, is
also of common occurrence near the pockets. As in most of the
gem-bearing pegmatites the tourmalines are seldom in their original
positions on the walls of the cavities, but lie embedded in a sandlike
mass of quartz fragments, cookeite, and other decomposition products at
the bottom of the pockets. They are mainly grass-green to olive-green
in color, becoming nearly colorless toward the tip. The exact apex of
some of the crystals is pink and many of them show very perfect
terminations. Gem tourmalines are not so abundant that it would pay to
work the mine for these alone.
Most of the gems found in the feldspar mining were marketed irregularly through local collectors.
The associated minerals and tourmaline from Haddam Neck have been described by H. L. Bowman,1
as pinkish muscovite, lepidolite, greenish-white muscovite, tourmaline,
apatite, microcline, albite, beryl, quartz, cookeite, fluorspar,
microlite, and columbite. The tourmaline occurs in beautiful,
transparent, striated, curved triangular prismatic crystals of various
colors, the most common being light and dark green and pink. A few
crystals are almost perfectly colorless. Color variations in the
crystals are generally in transverse bands, either with sharp contacts
or hazy gradations. In some crystals the color shades are delimited by
planes corresponding to crystal terminations, yielding ghost or phantom
crystals. Kunz states that crystals showing marked internal striations
have been found which yield gems showing cat's-eye effects when cut
cabochon across the prism. This property has also been found highly
developed in some of the tourmalines from Mesa Grande, Cal.
The feldspar quarry of F. E. Strickland is about 2\ miles
northeast of Portland, in the west side of Collins Hill. It is operated
by Mr. Strickland under lease to the Eureka Mining & Operating Co.,
of Trenton, N. J., all of the spar, quartz, and mica going to the
company and gems and other minerals being retained by Mr. Strickland.
The quarry consists of two joining open cuts with north and south
elongation, parallel, and connected at the north end. The east cut is
about 300 feet long, 65 feet wide, and 10 to 40 feet deep. The west cut
is about 200 feet long, 50 feet wide, and 25 feet deep. A crosscut
leads out to the hillside at the north end of the west cut.
The
country rock is muscovite-biotite schist containing much black
tourmaline near the pegmatite. The schist has a general north strike
and a dip of about 20° W. It has been warped, however, to correspond
approximately with the contact of the pegmatite. The pegmatite is a
large irregular semibedded deposit both parallel with and cutting the
schist in different parts. In the east deposit the outcrop was an
elongated dome pitching under the schist at each end. That this body of
pegmatite joins the one forming the west deposit under the surface is
shown where the two open cuts join at the north end.
The
pegmatite is coarse-grained containing large bodies of graphic granite,
potash feldspar crystals 2 or 3 feet across, irregular quartz
segregations several feet thick, and bunches or streaks of mica
crystals. Cavities or pockets with crystal-lined walls are found
irregularly distributed in parts of the quarry, especially in the east
working. These pockets range from small size up to one reported to be 4
feet long by
i
Mineralog. Mag. and Jour. Mineralog. Soc. Great Britain, vol. 13, pp.
97-121,1903. Reviewed by G. F. Kunz, U. S. Geol. Survey, Mineral Resources U. S., 1902, pp. 841-842,1904.
