have
a bluish tinge, in some cases quite deep, and are from i to 5
millimeters (.039 to .196 inch) in thickness. Hoffman mentions
corundum occurring in fragments near Silver Peak, Nev.1 Rubies
and sapphires have been erroneously reported to be found in the surface
sands and gravels of Arizona and New Mexico, associated with the pyrope
garnet.
SPINEL
crystallizes
in the isometric system, and is generally found in the form of
octahedrons. Its hardness is 8 and its specific gravity about 3.65.
Following the order of the rainbow, it exists in all shades of red,
orange, green, blue, and indigo, as well as white and black. The
crimson and flame-red colored varieties are exceedingly beautiful. The
red is called ruby spinel, and fine stones command high prices. Spinel
is found associated with ruby in Burmah, Ceylon, and Siam. Its
composition consists of one molecule each of alumina and magnesia,
equivalent to 72 per cent, of alumina and 28 of magnesia
Spinel
fine enough to cut into gems has been only occasionally met with in
the United States. The Rev. Alfred Free of Toms River, N. J., had in
his possession at one time cut gems of a smoky blue or velvety green
and a dark-tinted claret color, from the locality near Hamburgh, Sussex
County, N. J. They were all good specimens, weighing about 2 carats
each. Some half dozen from San Luis Obispo, Cal., of very good quality
and weighing about 2 carats each, were brought to the notice of the
writer by James W. Beath, of Philadelphia, Pa. Silas C. Young, who, for
over twenty years has collected minerals in Orange County, N. Y.,
writes that in his extensive working for minerals he has found small
ruby spinels, also others of a smoky and purple tint, sufficiently
clear to cut. The locality at Hamburgh, N. J., was discovered by his
father over fifty years ago.
The
region of granular limestone and serpentine in which spinels abound
extends from Amity, N. Y., to Andover, N. J., a distance of thirty
miles. Monroe, Norwich, and Cornwall, N. Y., are well-known localities.
The finest crystals from the locality known as Monroe, N. Y, are in the
Vaux and Bement Collec-
1 Mineralogy of Nevada.
