Its specific gravity is from 3 to 3-4. It possesses double refraction in a high degree, as its refractive power is 11°.
Although
not very hard, it takes a very bright polish, which, however,
diminishes in a short time. It is divided into Oriental and Western.
It
is found in pebbles in Ceylon, in Persia, Egypt, and Bohemia. In
Greenland it is disseminated in the masses of magnetic iron, and
between the large plates of mica, in the form of greenish or reddish
grains. In the Azores it is not a defined crystal, although always
transparent.
The
peridot is cut in the same manner as the emerald, and is sold by the
carat at a very low price, unless it happens to be of extraordinary
beauty.
Very
often sets of tormaline are brought from Ceylon and sold as peridots;
but this fraud can be easily discovered by means of the magnetic
property.
The peridot was known to the ancients, but we do not know by what name.
