Four Treasures Reference Database
Record No. 6223
Discovery of the Red Sea source of topazos (ancient gem peridot) on Zabargad Island, Egypt
Conference Paper
Thoresen, L. and Harrell, J.A. (2014) Discovery of the Red Sea source of topazos (ancient gem peridot) on Zabargad Island, Egypt. Twelfth Annual Sinkankas Symposium • Peridot and Uncommon Green Gem Materials, 5-Apr-14, Carlsbad, CA: Pala International, pp. 16–30.
Sinkankas/Born No.: NIS/NIB | RWHL*
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gems, peridot, beryl, emerald, Red Sea, Egypt, Zabargad Island
Peridot is the name for gem olivine, an iron–magnesium silicate ([Mg,Fe]₂SiO₄) in solid solution series with end members forsterite (Mg₂SiO₄) and fayalite (Fe₂SiO₄) (see: W. Simmons, p. 12 in this volume). Its color, density, and refractive index are related to the relative proportions of magnesium-rich forsterite and iron-rich fayalite. High-quality gem peridot is transparent with a green to yellowish-green color, but it can be translucent, and with increasing Fe content it tends toward a more brownish color. Measuring 6.5–7 on the Mohs hardness scale, peridot is easily abraded and is susceptible to etching by body oils. A selected bibliography of literature on peridot and its sources is given by J. Shigley in this volume (p. 120), and a world map of gem peridot localities is shown on p. 66.