Gems & Gemology, Summer 1997, Vol. 33, No. 2
Update on Emeralds from the Sandawana Mines, Zimbabwe
J.C. (Hanco) Zwaan, Jan Kanis, 和 Eckehard J. Petsch
Zimbabwe’s Sandawana mines have been an important producer of emeralds for 40 years. Since the mines came under new ownership in 1993, consistent production has been established and, in addition to the small sizes for which Sandawana is known, greater numbers of polished stones as large as 1.50 ct have been produced. Currently, mining at the most active area, the Zeus mine, is done underground, with the ore processed in a standard washing/ screening trommel plant. Sandawana emeralds can be readily separated from emeralds from other localities. They have high refractive indices and specific gravities. Two amphiboles, actinolite and cummingtonite, are abundant inclusions; albite and apatite are common. Also found are remnants of fluid inclusions. Chemically, Sandawana emeralds typically have a very high chromium content.