ENGRAVING UPON THE TURQUOISE. 143
is a substance altogether special in its composition, and above all in its organic origin.
It
is, in point of fact, a fossil ivory, produced from the teeth of a past
race of animals, brought accidentally in contact with substances
containing copper, and which has absorbed a sufficient quantity of
them to colour the entire mass with a cerulean hue more or less deep.
ENGRAVING UPON THE TURQUOISE.
The
low degree of hardness possessed by the turquoise probably deterred the
ancients from often engraving on this stone, or, it may be, these
specimens of antiquity have not been sufficiently durable to reach our
time. In either case, there are very few engraved turquoises known.
Caire, however, cites a few.
In
the Genevosio collection there is an amulet, convex on one side and
flat on the other, showing upon one side an engraving of a veiled Diana
holding two branches in her hands, upon the other a sort of sistrum, a
star, and a bee: Greek letters are inscribed upon both faces.
The
cabinet of the Duke of Orleans contained two engraved turquoises; one
representing Diana, with her quiver upon her shoulder; and the other,
the elder Faustina.
A turquoise in the gallery of Florence, nearly as
