These
are often gathered by the Comanche Indians. Pyrope garnet is also
reported from the State of Sonora. At Trumfo, Lower California,
beautiful garnets, in crystals of 1/8 to 1/2 inch in diameter, are said
to occur in a white rock. These are probably not of value. A. B. Damour
describes essonite, with a specific gravity of 3.57, in light-red
dodecahedral crystals in a granular limestone, from Rancho de San Juan.
Iolite
or dichroite is reported as associated with beryl in Tajupilco, in the
State of Hidalgo, and it is said to occur on the hill of Cerro Gordo in
Guanajuato.
The
name " jade " is popularly applied to several distinct ornamental
stones, but since A. B. Damour's investigations into the character of
jade, jadeite, and chlormelanite, the term has been restricted
mineralogically to what is specifically known as nephrite. Many
bric-a-brac dealers never distinguish between jade and jadeite, calling
both simply jade.
The
word "jade" is evidently a corruption of the Spanish " ijada," since
the mineral is first mentioned under this name in the writings of
Monardas in 1565, and was brought from Mexico and Peru under the name "
Piedra de ijada," or " Stone of the Loins," in allusion to its supposed
curative properties in diseases of the loins and kidneys. Amulets of
jade-like minerals have always been highly venerated by the natives
throughout Central America, Mexico, and Peru.
Jade,
or nephrite, is a silicate of calcium and magnesium. It has a specific
gravity varying from 27 to 2.9, a hardness of 6.5, and is extremely
tough, more so than jadeite. It may be described as a cryptocrystalline
variety of hornblende, exhibiting no crystalline form or cleavage, with
a splintery fracture, like horn. The color is generally uniform,
commonly either white or green, occasionally yellow or brown, very
rarely with a bluish or pink tint. Jadeite is a silicate of aluminum
and sodium. Its specific gravity ranges from 3.25 to 3.35, and it has a
hardness of 7. It has a crystalline structure, is not as tough as jade,
and its composition places it nearer to epidote than to hornblende. Its
lustre is more brilliant than that of jade. It is generally white,
occasionally greenish, with veins or spots of almost emerald-green
color, also lettuce-green and sage-green. In 1865, Damour, who
originally
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