On
the whole, therefore, Precious Stones may be arranged in three classes,
as determined, each by its main basic chemical elements ; these
elements being more or less medicinal, as we shall categorically, and
succinctly endeavour to show.
The said three classes are :—
1. The Carbon Class.
2. The Alumina Class.
3. The Silicon Class. '
To
the First Class, or Group, which is characterised by Carbon, as a
common base, only one Precious Stone belongs, viz., the Diamond, which
consists of pure carbon, sublimated, and crystallised to the acme of
excellence.
Class,
or Group the Second, includes all the Sapphires (properly so called),
among which are the true Sapphire, the Oriental Ruby, the Oriental
Emerald, the Oriental Topaz, and the Oriental Amethyst. All these are
composed of pure alumina, coloured in different ways.
Class,
or Group Three, includes the Opal, the Amethyst, and the Agates,
(amongst which are the Cornelian, the Chalcedony, the Onyx, the
Sardonyx, and the Bloodstone). These are all made up chiefly of silica.
Between
the Alumina Class, and the Silica Class, are several kinds of stones
which are composed partly of alumina, and partly of silica (united with
some other substances). Among these are the true Emerald, and the true
Topaz, which differ from the Oriental Emerald, and the Oriental Topaz.
Other stones, such, for instance, as the Garnets, are made up of
various substances, and are of. minor value as Precious Stones. The
Pearl, Coral, and Amber, also Malachite, the
