gems, turquoise, odontolite, Persia

René-Antoine Ferchault de Réaumur’s paper is an early scientific investigation of French turquoise deposits and the origin of turquoise color. He describes the occurrence and working of turquoise-bearing material, examines specimens and their physical characteristics, and investigates the substance responsible for their blue and green coloration. Of particular gemological importance is his recognition that some material sold as turquoise consisted of fossil bone or teeth whose original substance had been altered and colored by mineral solutions—the material later known as odontolite or “bone turquoise.” The paper represents an important early attempt to distinguish true turquoise from visually similar materials through observation and experiment and contributes to the developing scientific understanding of gemstone composition, coloration, and imitation in the early 18th century. Sinkankas: Established that certain so-called turquoises (odontolites) were actually stained fossil teeth.