of an orthoclase sunstone were found, almost as fine as any of the Norwegian.
Obsidian.—Smoky,
transparent obsidian that would cut well, and form a curious variety
somewhat resembling the "Moravian bottle glass" (moldavite), but not so
green, has been found in rounded pebbles, over 1 inch across, near
Santa Fe, Mew Mexico.
A
porphyritic and spherolitic obsidian is found under the trachyte on
Gunnison river, and a heavy vein of porphyritic obsidian near the Rio
Grande pyramid, continuing from there southward through the trachytic
bed. Nodules occur in the lower members of the trachytic veins.
Adike
of obsidian, light gray and clear with concentric structure, sets from
the Colorado Central lode near Georgetown, north of Saguache creek.
Hoffmann mentions obsidian in fine pieces and very abundant as
occurring 10 miles southeast of Silver Peak, Nevada. Across the State
line, 5 miles in Owen valley, California, it is found in red fragments,
and also banded with alternate layers of black and brown. Obsidian
occurs in large, fine black pieces, and mottled black and brown, and
in small layers, in a moss rock at Obsidian cliffs, Yellowstone park.
Octahedrite.—Octahedrite
is reported as occurring in small crystals at Dexter's lime rock at
Smithfield, Rhode Island, and in flat tabular glassy crystals of a pale
green color and very brilliant in the gold sands of the Brindletown
mine(a), Burke county, North Carolina. These would possibly afford
small gems, nothing, however, to compare with the beautiful blue
crystals from Brazil, so splendent at times as to be mistaken for
diamonds.
Brookite, arkansite, microlite.—At
the Ellenville, Ulster county, New York, lead mines some remarkable
flat, ruby-red crystals of brookite have been found, and at Magnet
cove, Arkansas, remarkably brilliant crystals of the variety of this
mineral known as arkansite occur in great profusion, at times a
transparent honey yellow. The mineral does not, however, readily admit
of polish. One fine crystal of microlite in the cabinet of Mr. C. S.
Bement, is about three-eighths of an inch long, and in part a rich
honey-yellow color, having all the color of topazolite, with a higher
luster. This might possibly be added to the list of American gem
minerals. This crystal was found at Amelia Court House, Virginia. Some
few of the microlites found at the Amelia Court House locality are of
sufficient transparency to afford gems, the color ranging from an
essonite red to that of a rich spinel yellow and remarkably brilliant.
Microlite has the highest specific gravity of any known gem, being about 6.
Ilmenite.—At
Magnet cove, Arkansas, the ilmenite is found in such fine bright
crystals as to form natural ornaments, and will, besides, admit of a
fine brilliant polish.
a " Minerals and Mineral Localities of North Carolina," 1881 page 84.
