662 MINERAL RESOURCES, 1913—PART II.
level
a few feet above the lower cuts, but still 18 or 20 feet lower than the
summit of the knoll. The country rock is biotite gneiss carrying much
black tourmaline near the pegmatite. The gneiss has been strongly
folded and crinkled near the pegmatite and accordingly has a variable
strike and dip. The pegmatite is very irregular in shape, having a
westerly trend across the knoll. It incloses streaks of biotite
gneiss, and the surrounding gneiss has been injected by many small
lenses and streaks of pegmatite. The pegmatite contains large
segregations of gray and smoky quartz, some graphic granite,
ortho-clase and albite feldspar, pockets or bunches of mica (both
muscovite and biotite), black tourmaline, green apatite, a few red
garnets, and numerous beryl crystals. A quantity of mica of good
quality was obtained during rnining.' The beryl crystals range up to a
foot in diameter and are vari-colored; some are bluish, bluish green,
yellowish green, and light and dark golden yellow. Much of the beryl
is translucent, and parts of some of the crystals are transparent and
flawless so that perfect gems can be cut from them. Small dark golden
beryl of exceptional beauty has been cut from clear portions of large
crystals. Much of the translucent beryl could be used to advantage for
cabochon gems and beads.
Beryl
Mountain, in the town of Acworth, N. H., has long been famous for the
size and abundance of its beryl crystals. According to Mr. Eugene
Crossett1 owner of the prospect, an attempt was made
in 1884 to quarry a large beryl crystal here for use as a tombstone
over the grave of Emerson at Concord, Mass. Difficulty was experienced
in removing a crystal without fracturing and the attempt was abandoned.
Later a bowlder of rose quartz was adopted for this purpose. Mr.
Crossett states that some specimen beryl was removed at this time and
a quantity of feldspar and quartz were shipped for the manufacture of
pottery, glass, and sand paper.
Beryl
Mountain is a steep-faced hill or ridge rising about 200 feet above the
road around its base. It has a north-northeast trend and is narrow near
the summit. Prospects have been opened on the east side of the northern
end about 25 feet below the summit and on the summit above. The work on
the summit consists of several pits now badly overgrown by vegetation.
The principal work is an open cut or small quarry about 25 feet long,
15 feet wide, and 10 to 12 feet high in the hillside. This cut has a
cavern-like face 8 to 10 feet high with an overhanging ledge above.
The
beryl occurs in a pegmatite mass cutting the mica gneiss country rock.
The pegmatite and the inclosing formations appear to strike with the
trend of the hill, but no minerals of interest were observed in the
outcrop to the south of the prospects. The open. cut has been made in a
deposit of mixed oligoclase feldspar and quartz through which are
scattered numerous beryl crystals and a little muscovite mica. This
deposit is capped by a massive bed of granular sugar quartz mostly pure
white or tinted with pink. In places this quartz is glassy and
translucent, and some has a pale rose color. The contact between the
massive quartz and the beryl matrix is not distinct, but the massive
quartz grades into that associated with the feldspar and beryl. Several
feet below the massive quartz, feldspar is more plentiful than near the
quartz. In an exposure of the quarry face measuring about 16 feet long
and 8 feet high 35 large beryls
Personal communication, dated South Acworth, N. H., Mar. 2,1914.
