It
is the breaking down of these veins that form many of the smaller often
microscopic minerals found in the detritis of the gold veins.
THE FELDSPARS.
Several
interesting varieties of feldspar occur in North Carolina, among which
the following may be especially noted as the ones which are of
importance as gem material.
Orthoclase.—A
very interesting variety of sunstone was found by J. A. D. Stephenson
at the quarry in Statesville, N. C; the reflections are as fine as
those of the Norwegian, but the spots of color are very small. Several
hundred dollars' worth from this locality have been sold as gems.
Microline.—This
feldspar is closely related to orthoclase; it is sometimes of a very
beautiful light green color, and is then known as amazon-stone, and
valued for cutting and polishing for ornamental purposes. Several
localities in North Carolina furnish this mineral, especially the Kay
mica mine, Yancey County.
Oligoclase.—In December, 1887, specimens of feldspar were sent to the writer2
by Daniel A. Bowman, who had found them at a depth of 380 feet in the
Hawk Mica mine, 4 miles east of Bakersville, N. C. They proved to be a
variety of oligoclase, 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; these tufts vary 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 § inch to § inch (10 to 15 millimeters)
across, which were as colorless and pellucid as the finest phenaeite
and entirely free from
2 See Mineralogical Notes, by George F. Kunz, Am. Jour. Sci., Ill, Vol. XXXVI, p. 222, Sept., 1888.
