Their origin and formation. 125
by Pearls had attracted the notice of the ancient Romans and led to a systematic nomenclature. The Unto was the name of the globular Pearl; the tympania of the hemi-spherical; the elenchus of the pear-shaped ; and the margaritum of the irregular or baroque Pearl.
The
baroque Pearls often assume very whimsical forms, and advantage has
sometimes been taken of this fact by mounting the warty Pearls as
grotesque ornaments. Dinglinger, the court jeweller at Dresden in the
latter part of the seventeenth century» was famous for his ingenuity in
this direction, and some beautiful specimens of Pearl mounted in gold
and enamel may be seen in the Jewel Room of the Green Vaults at Dresden.
The
chemical composition of the Pearl as previously stated is carbonate of
lime associated with a small proportion of organic matter: it is easily
affected by acids and fetid gases and may be calcined on exposure to
heat. It possesses a lustre peculiar to itself which is known as the
"orient.'' Its specific gravity is, 2.5 to 2.7, those found on the coast of South America, termed Panama Pearls, being somewhat denser than the Oriental Pearls.
The beauty and value of Pearls depend on their
