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Introduction.
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fortuitous
circumstances which are required for the formation of these beautiful
crystals, to give them the required transparency, brilliancy, and
lustre, the freedom from defects and flaws, and the presence of the
exact quantity of colouring matter to furnish the desired tint, it
will be no matter of astonishment that they occur so seldom; and the
idea that one day precious stones may become as plentiful as marble
may be dismissed as groundless, when the numerous qualifications which
are necessary for a stone to enter into this aristocratic and exclusive
family are considered; for there must not only exist the
crystallization to give the required form, but the hardness to allow of
the proper polish and lustre, and the colouring matter to produce the
desired hue; and should one of these requisites be wanting, the gem
loses its value in the eye of the connoisseur.
The
minerals which are the component parts of gems are plentiful throughout
the globe; we can obtain magnesia, glucina, alumina, metallic oxides,
etc., in profusion, and we can separate the gems themselves into their
.component parts; but, not all the researches of learned chemists, not
all the accumulated science of the nineteenth century, has succeeded in
wresting the secret from nature, or of producing them of any size or
value by artificial means. The material of the diamond, for instance,
"carbon," is found almost everywhere,—in the bread we eat, in the coal
and wood we burn; uncrystallized, it is brittle and opaque,
B 2
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