ORIGIN, PROPERTIES, CLASSIFICATION-, ETC. 2$.
Imitating precious stones by glass mosaics was an art
understood by the ancient Greeks and Romans, which has been
transmitted to their successors, and has become an important
industry in modern Rome, Florence, Venice, and Sèvres.
Venice, for many centuries, has enjoyed a monopoly for the
production of aventurine, while the manufacture of imitation
diamonds at the "Crystal Works of the Jura" is said to
require the labor of a thousand or twelve hundred operators.
During the Augustan age and for two centuries later, the
art of making paste jewels was carried on to a great extent, but,
as a natural consequence, it went out of use on the decline of
genuine work. It was not, however, exterminated, for at the
Renaissance, when new vigor was imparted to all departments
of art and learning, the occupation of making imitations
became a profitable branch of industry, as may be inferred
from the great number of spurious gems found in mediaeval
buildings and collections. Many of those used to embellish the
churches of to-day are pastes, which have been substituted for
the real gems to avoid any temptation for robbery. Those
employed to ornament the sacred vessels of the Cologne
cathedral are suspected of being imitations, as well as the onyx
carnei of the " Shrine of the Three Kings."
Stringent laws have been enacted at different times against
counterfeiting gems ; but in every instance they have been
successfully evaded. And so long as they are prized as the
most valuable of earthly possessions, frauds and imitations in
their production and sale will continue to be practised.
Deceptions occur not only in the nature of the stone, but,
also, in the manner of setting, by combining a genuine and a
paste, or an inferior with a superior gem, as when a stone, cut
as a " double," has the upper part garnet, for instance, and the
lower glass, an artifice very difficult to detect. Garnets backed
