GEMS AND PRECIOUS STONES. 683
NEW HAMPSHIRE.
The discovery of topaz on Baldface Mountain, N. H., was made, according to George F. Kunz,1
by E. A. Andrews, in May, 1888. Baldface Mountain is about 4 miles
northwest of North Chatham. It rises to an elevation of 3,585 feet
above sea level or some 3,000 feet above the valley of Cold Kiver on
the east. Only rock is exposed on the steep cliff-like slopes of the
upper part of the mountain, but the lower part is heavily timbered. Two
knobs or shoulders project from the mass of the mountain half a mile
northeast and southeast, respectively, of the main summit and 500 to
600 feet lower down. It is on these knobs or shoulders of the mountain
that the topaz has been found.
The
bare rock of the upper part of the mountain is composed of biotite
granite, partly broken into great loose blocks and partly showing the
effects of rounding and erosion by the ice of the glacial epoch. Near
the east foot of the mountain outcrops of mica schist and gneiss were
observed in the hollows.
No
systematic mining has been carried on for the topaz and associated
minerals, but most of the crystals have been obtained at various times
by prospectors and mineral collectors working only a few days at a
time. Considerable prospecting for topaz and associated minerals on
Baldface Mountain has been done by John Chandler, of North Chatham. Mr.
Chandler acted as guide for the writer, and three prospects were
visited. Two of these were on the northeast shoulder of the mountain in
the steep cliff-like slope, and the other was on the southeast shoulder
of the mountain. The two prospects on the northeast shoulder are a few
hundred feet apart in a northeast-southwest direction with a difference
of elevation of 200 to 300 feet. At the Upper prospect the topaz occurs
with crystals of smoky quartz, orthoclase or microcline, biotite,
muscovite, and a little phenacite lining the walls of miarolitic
cavities or pockets of pegmatite in the granite. These pockets range
from small to large size, one measuring 10 feet deep (or high) and 2
by 3 feet across at the top and 4 by 7 feet across near the bottom. The
pockets have been worked in a northeast course down the mountain side
for a distance of nearly 50 feet. The granite near the pockets is
medium to coarse grained, rich in biotite and smoky quartz. The
crystals lining the walls of the pockets range from small size to 2 or
3 inches across, in the case of the feldspar. The transition from the
ordinary granite to the coarser, more crystallized deposit forming the
walls of the pockets is gradual in some places, and in other places
there is a layer of fine tufted graphic granite between.
Some
of the feldspar crystals have a faint bluish-green color, like pale
amazon stone. Others are buff colored, but present well-developed
crystal faces. Most of the quartz crystals found in the pockets are
smoky brown and many are clear. Some occur in single well-developed
crystals and others in aggregates of crystals in parallel growths. In
the cavities biotite occurs in sharply developed prismatic crystals
with hexagonal outlines. The topaz occurs in crystals of minute size up
to those more than an inch thick. The majority of them are translucent,
or transparent only in places, but some perfectly transparent crystals
are found. Some of the topaz is suitable
i Gems and precious stones of North America, p. 70,1890.
