varieties of less value are found in Thibet, China, Silesia,
Saxony, the Isthmus of Suez, Mexico, and the United States.
It has been claimed that Russia yields the turquoise, an error
easily made, since much of it is cut and polished at Moscow
and sold at the great fair of Nijni-Novgorod by Persian and
Turkish merchants.
The variety recently discovered at Mount Sinai, Arabia, is
unrivalled in its fine blue color when first mined, but it
changes its hue in some mysterious manner, a tendency shared
by the Persian and other kinds, though in less degree.
Antique engraved turquoises are known to have retained their
original freshness of color.
The Mexicans were familiar with the use of this substance,
and probably obtained it from their own country. It has been
found in New Mexico, at Turquoise Mount in Arizona, and in
Nevada, in the United States. The specimens from the latter
place are of a rich blue, approaching in quality the finest
Persian, but are of minute size ; those from New Mexico are
green, and were highly valued for ornaments by the original
inhabitants. The mines in this territory were worked by the
Spaniards two hundred years ago, and from them were taken
many of these gems found in the crown jewels of Spain.
Some mineralogists have divided the turquoise into what
they call " Old Rock," comprising the oriental or superior
kind, which retains its color, and is found in irregular masses,
and the " New Rock," of a pale tint, inclining to white, a much
less valuable and beautiful variety.
The different analyses of the turquoise have hitherto given
different results, but phosphate of alumina, oxide of copper,
and iron, are invariably present; \vater, manganese, and lime,
have been added to these constituents, though the composition
varies in different localities. It is compact, without crystalliza-
