ditions of the craft from the date of the Empire. Besides making pastes of smalts, exact
counterfeits of the true gems, they converted the commoner stones into
others of the most precious kinds, by such ingenious processes as that
of cutting a Garnet very thin and backing it with Crystal to pass for a Ruby ; an Amethyst hollowed out and filled with a coloured tincture
imitated the Balais, which was also counterfeited by a thin table of
the former laid upon a ruby-foil. Diamonds they forged by cutting the
Beryl or the White Sapphire to the proper shape (a pyramid), and
backing them with the customary tincture. To explain the latter term,
it must be borne in mind that formerly the Diamond was always coloured
black upon the ciblasse, with a certain composition, on the
proper nature of which Cellini treats at great length in his '
Orefeceria,' as being of the utmost importance to the effect of the
gem. In order to escape the test of the file, which no paste can
endure, these early Italian forgers imitated above all the rest the Emerald and the Peridot, for, these gems being but little superior in hardness to pastes, such a means of detection could not be applied to them.
it has been remarked above that no antique intagli in this stone are
known to exist, yet there is an epigram by Diodorus (Anth. ix. 776)—"
Upon an engraved Crystal."