|
UNITED STATES, CANADA AND MEXICO
|
167
|
||
|
|
|||
|
very
fine gem stone, differing from labradorite and moonstone, the
chatoyancy being an intermediate one between the white of moonstone and
the dark blue of the former. It occurs in large masses at Cavendish,
near Cavendish Falls, in the railway cutting, twenty-two miles
northeast of Bellows Falls, Vt.
A
compact variety of white or gray orthoclase, spotted black by hydrated
manganese oxide, and called from its leopard-like appearance,
leopardite, is abundant near Charlotte, Mecklenburgh County, and also
in Gaston County, N. C. It is a variety of porphyry with disseminated
crystals of quartz, and occurs in large masses as a rock, so that it
would furnish a good ornamental stone, if polished. It might be also
used for a gem stone.
In
December, 1887, specimens of feldspar were sent to the writer' for
examination by Daniel A. Bowman, who had found them at a depth of 380
feet in the Hawk Mica Mine, four miles east of Bakersville, N. C. They
proved to be a variety of oligo-clase, remarkable for its transparency.
The clearest piece measured 1 by 2 by 3 inches. One of the two
varieties is of a faint window-glass green color, and contains a series
of cavities, surrounded and fringed by tufts of white, needle-shaped
inclusions called microlites, which measure from 1/50 to 3/50 inch (0.5
to 1.5 millimeter) in diameter and are quite round, resembling those
that are occasionally present in the Ceylonese moonstone. The
wonderful transparency of the oligoclase and the whiteness of the
inclusions give the whole mass a striking resemblance to the lumps of
glass so commonly obtained from the bottom of a glass pot. It was
mistaken for this until its highly perfect cleavage was noticed.
Recently some material of a slightly different character has been
obtained at the mine. Cleavage masses of a white, striated oligoclase,
3 inches long, were found, containing nodules about 2/5 inch to 3/5
inch (10 to 15 millimeters) square, which were as colorless and
pellucid as the finest phenacite and entirely free from the inclusions
found in the greenish variety. This transparent variety, like the
other, shows no striae.
The
following analysis by Prof. Frank W. Clarke, made from a faint green
variety, shows it to be a typical oligoclase. The specific gravity was
determined to be 2.651. This has been
1 See Mineralogical Notes, by George F. Kunz, Am. J. Sci. III., Vol. 36, p. 222, Sept., 1888.
|
|||
|
|
|||