Emerald mining district, Red Sea Governorate, Egypt
Ancient emerald mines (2000 B.C. - 1200 A.D.). Rediscovered 1818. Egypt was the source of almost all emerald in ancient times.The area is underlain by quartz-micaceous, hornblende, biotite, and talc schists, crumpled into complex folds and squeezed between a massif of the late Gattar gneissic granites and serpentinites. Emerald-bearing biotite and biotite-amphibole-talc schist horizons are up to 10 m thick.
The emerald crystals are generally small, and most contain fissures and numerous inclusions. Their colour is light green, occasionally bluish green. Associated minerals including those that form inclusions in the emerald, are biotite, quartz, hornblende, less abundant plagioclase, tourmaline (schorl), garnet, magnetite, and calcite. Gas-liquid inclusions often contain carbon dioxide.
Ref: E.Ya.Kievlenko, Geology of gems, 2003, p. 86