The
gold recovered from concentrates is mostly fine, though nuggets worth
several dollars have been reported. It is said the value of the gold
obtained is sufficient to pay operating expenses. The larger part of
the sapphire, either on account of small size or poor color, is
suitable for mechanical purposes only, as watch and meter bearings.
Some of the sapphires are suitable in size, quality, and color for
cutting as gems. The predominant colors of the Dry Cottonwood
sapphires are deep and light aquamarine and pale yellowish green. Other
colors are clear and smoky blue, light and dark topaz yellow, straw
yellow, yellowish green like olivene, light and dark pink; some stones
are nearly ruby red, lilac and pale amethystine, and some are
colorless. The pleochroism of some of the sapphires is marked, the same
crystal appearing greenish when viewed across the prism and blue
through its length, or pale and deeper pink, as the case might be. It
is not unusual to find aquamarine-colored stones with a pink spot in
the center. This combination furnishes an attractive gem when cut. A
feature of the deep pink colored sapphires is their rich and beautiful
color under artificial light, even when not very attractive in natural
light.
The
sapphires occur in rough crystals, often with curved faces, as
irregular rounded masses, and as waterworn pebbles. The surfaces of
those which are not waterworn are very much etched and corroded. One
yellowish-green sapphire crystal, weighing a little over 4$ carats, had
very much the shape of a rough diamond crystal. This effect is largely
due to the fact that the development of the basal and rhombo-hedral
faces produced a form resembling an octohedron. This apparent
octohedral form along with marked curvature of the faces and peculiar
etching produces the effect described. The proportion of waterworn
sapphires is not large, and only a few show a large amount of wear. A
few red and cinnamon-red garnets, mostly small, are found in the
concentrates with the sapphires.
American Gem Mining Syndicate.—The
operations of the American Gem Mining Syndicate for sapphires were
confined to two gulches on the north side of the West Fork of Rock
Creek, in Granite County, about 15 miles southwest of Philipsburg.
These gulches are nearly a mile apart and are known as Anaconda Gulch
on the west and Meyer Gulch on the east. Both drain to the south,
Anaconda Gulch with a rather steep grade cutting through a small
stretch of flat country along part of its course. Sapphires are said to
have been found in the gulches and scattered over the surface of an
area of about 2 square miles in this region.
The
country rock around the sapphire deposits consists of coarse and fine
grain porphyry, porphyritic tuff, conglomerate, quartzite, siliceous
slate, and black limestone, the geological relations of which have not
been worked out. In and near Anaconda Gulch the rocks underlying parts
of the sapphire deposits are conglomerate, porphyritic tuff resembling
conglomerate where the inclusions are plentiful, and porphyry. The bed
rock in the lower part of Meyer Gulch is a dense, siliceous slaty rock
of purplish color with a little black limestone. To the west of the
sapphire-bearing deposits on the flats near Anaconda Gulch is rather
coarse porphyry, probably granite porphyry, and to the north is fine
porphyry. Ledges of tuff or conglomerate outcrop at one place on the
flats where sapphires have been
