142 PRECIOUS STONES.
idea
that had prevailed in Europe, of the much vaunted turquoises of the old
rock. Perhaps the mine was already more or less exhausted.
Oriental Turquoise.—This is another aluminous stone; but alumina forms hardly more than half of its composition.
The
blue colour, so characteristic of the turquoise, is due, in great part
at least, to a combination of phosphoric acid, copper, and iron, and
probably also to water, of which it contains 18 or 19 parts in 100.
The
turquoise harmonizes well with diamonds and pearls, and is frequently
employed in jewelry. It is consequently an object of some commercial
consideration ; but as it is pretty abundant it does not reach a high
price, unless in specimens of a very unusual size.
At
the sale of M. Dree's cabinet, a turquoise of the old rock, measuring
47 inch by 43 inch, was sold for $93 ; and as an example of the wide
difference between the turquoises of the old and the new rock, there
was sold at the same sale, for $22'50, a turquoise of the new rock, 39
inch by '37 inch, of the most beautiful sky-blue tint.
The
turquoise is the stone that the orientals employ most frequently for
amulets. Sentences are frequently engraved upon them, and generally
quoted from the Koran.
Occidental Turquoise.—The occidental turquoise
