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2 Definition of the Term Precious Stone or Gem.
and
durability,, yet destitute of any beauty of colour or lustre, and
therefore unfitted for personal adornment. Colour alone is by no means
a necessary property in a precious stone : the Diamond, for example,
though presenting in some of its varieties every known tint, may be
absolutely destitute of colour ; nevertheless, it possesses the power
of breaking up the rays of light which fall upon it, or pass into its
substance, into rainbow-like tints of transcendent beauty. The Diamond,
in fact, unites the properties of the most opposite elements—combining
the purity of water with the flash of fire.
Precious Stones are frequently known also as Gems. It should be borne in mind, however, that this term is sometimes restricted by collectors of works of art to engraved stones—that is, to carnei and intagli, especially
those which have come down to us from classical antiquity or from
mediaeval times. It may, therefore, be convenient, in order to avoid
confusion, to refer to the precious minerals themselves as Gem-stones rather than as Gems.
It
is difficult to arrange the various Precious Stones in the order of
their relative value, since the order is subject to occasional
variation according to the caprice of fashion or the rarity of the
stones. Nevertheless it is believed that the following scheme, in which
all Precious ancT Semi-Precious Stones are grouped in five classes,
fairly indicates the relative rank which they take at the present day.
I. The Pearl stands
pre-eminent. It is true that this substance, being the product of a
mollusc or shell-fish, is not strictly a mineral. It is, however, so
intimately related in many ways with the family of true Precious Stones
that it properly claims a place in any classification such as that
under discussion. The Pearl has increased so greatly in value in recent
times, that if one of a certain size
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