Turquoises
of considerable size and occasionally of good colour are met with
having Persian and Arabic inscriptions or ornamental designs engraved
upon them. The hollows of the designs are sometimes gilt, sometimes
inlaid with gold wires.
The distinction between turquoises de la vieille roche and those de la nouvelle roche has
a real existence. The former, chiefly obtained from the Nishapur
district, are superior in quality of colour, even when the latter
belong to the same species, and are not, as is often the case,
identical with odontolite, or bone turÂquoise, or with variscite.
The
turquoises from New Mexico vary much in colour ; and if originally of a
fine blue do not invariably preserve their hue. Some of them contain
interspersed particles of quartz. No less than 7 per cent, of copper
oxide occurs in some of the stones from the Burro Mounts, Grant County.
CALLAINITE.
There
are three minerals passing under the name of turquoise. The true
turquoise is the callaite of mineralogists ; then there is a fossil
turquoise or odontolite ; and lastly we have a pale bluish-green stone
which has been described under the names callaie, variscite, and
callainite, and which presents a near relationship to the true
turquoise. Its hardness is 4 ; its specific gravity 2.55 ; and its
percentage composition :
There is another blue mineral related chemically to turquoise
