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TURQUOISE
This mineral
is known to scientists as " callaite." AlÂthough not transparent, its
beautiful color, and the fact that it is considered peculiarly suited
to blond complexions, make it a favorite jewel with many. The color,
equally good by artificial light, is due to phosphate of copper, of
which it contains, according to different analyses, two to eight per
cent. It is found only in compact form in irregular veins within a
matrix. It has no cleavage, and the fracture is conchoidal. Heat sweats
the water out of the stone and crackles it.
The
most celebrated mines are the Persian, and the turÂquoises taken from
them are renowned for their beauty and credited with holding the color
better than others, though the stones of different localities vary in
this respect, some fading badly soon after being released from the
matrix. The mines are situated in the northeastern part of Persia, in a
district of the Nishapur province, and the turquoise is taken from a
stratum of eruptive and altered rock at a height of nearly seven
thousand feet. An old mine called the Abdur-rezzagi produces the
finest. Many of the Persian turquoises lose color as they dry; others
change to a greenish tint. This is the prevailing fault of turquoises,
and though many are treated to preserve the color, and are guaranteed,
they are liable, under certain conditions, to turn more or less green.
And this is true of all turquoises, wherever they are mined. The mines
are worked in a careless and irregular way by the natives. There is an
abundance of good material, but the shafts and cuttings are so choked
with debris and in such a dangerous condition that no European cares to
make
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