Some specimens have lately arrived here from Australia, but they are not of good quality.
The
colour of the ruby varies from the lightest rose-tint to the deepest
carmine. Those too dark or too light are not esteemed. The most
valuable tint is that particular shade called by j ewellers the "
pigeon's blood,'' which is a pure deep rich red, without any admixture
of blue or yellow.
The
stones called spinel and balas rubies are not rubies at all, but
belong to the class of spinels, a stone of an entirely different
nature, and form of crystallization. Many of these stones are sold by
fraud or error for the true or Oriental ruby, but the difference may be
easily detected, both by the different specific gravity and hardness.
Several of the gems sold for Ceylon rubies are spinels, and even many
persons in the trade are not aware of the difference. In ancient times
the words ruby and carbuncle were applied indiscriminately to all red
stones, and even now the words are frequently applied to various gems.
The tourmaline is called a Brazilian ruby, when of a red colour ; the
same term is also occasionally given to the artificially coloured
topaz. This loose nomenclature is very apt to deceive the
inexperienced, who imagine a ruby only to mean the oriental corundum.
Some very interesting experiments have lately been made by chemists,
who have succeeded in forming by artificial means, minute crystals of a
red colour, of precisely the same form of crystallization, and of equal
hardness to the natural ones, but as the
