gems, turquoise, Iran, Persia, Persian turquoise

An early mineralogical study by Gotthelf Fischer of two very different substances historically called turquoise. Fischer distinguishes “oriental turquoise,” which he regards as a true mineral, from “occidental turquoise” or turquoise odontolite, which he identifies as fossil tooth or bone colored by a copper compound. He proposes the name calaite for the mineral turquoise and discusses its occurrence, physical character and historical nomenclature, comparing it with Pliny’s descriptions of callais. Fischer notes that calaite occurs as rounded pieces in alluvial deposits rather than in a rocky matrix and discusses its resemblance to emerald and sapphire in ancient descriptions. The work is important in the history of gemology for its attempt to separate true mineral turquoise from odontolite and to reconcile contemporary mineralogical observations with the terminology of classical lapidary sources.