4 NATURAL HISTORY OF PRECIOUS STONES, &c.
their
varieties, also of the Carbuncle, Lyncurium, and Amber; 30-35, of the
inferior Gems, also used for signets;* 36-39, of Pearls, Coral, Gold
and Silver ore.
The
Second Part of the Treatise describes the Earths used in the arts,
Ochres of various colours, and other pigments; 40-42, of the
composition of Minerals in general: as formed either of earth or sand,
or lime, and of their distinctive properties ; 43, 44, of Gem-engraving
and the substances used therein: the Armenian-stone (Emery); 45-47, of
Touchstone, and the Assaying of Gold; 48, 49, of Earths in general,
Glass, Copper-ore, Bitumen ; 50-55, of Ochres and Azure; 56, 57,
White-lead and Verdigris; 58-60, of Cinnabar and Quicksilver ; 61-63,
of Pigments, and where found; 64-69, of Gypsum and Stucco-work.
The
treatises, however, of Sudines, Sotacus, and Zeno- . themis were, as
Pliny's extracts show, confined to the subject of the Precious Stones
and Gems. Sotacus must
have been earlier than Alexander's period, for the reason above adduced ; the others may be supposed to have flourished
under the Ptolemies, when Alexandria had become the grand entrepôt of
the Indian trade. Some of them appear to have visited the gem-producing
regions as jewellers and merchants (like Tavernier and Chardin on the
mission of Louis XXV.), for the quotations from their works bear the
stamp of practical precision.
