Afghan Ruby: Gemstone Information
Afghan ruby deposit in the southern portion of the Sorobi district, 60 km south-east of Kabul in the Jegdalek river valley. They attribute ruby formation to the contact metasomatism of ultra-acid granites found in contact with Precambrian carbonate and magnesium rocks in the Pamir-Nuristan median mass. Ruby mineralization is irregularly developed. Gem ruby is found in situ in interstratified Proterozoic marble and gneisses intruded by granitic rocks from the Oligocene. The ruby-bearing marble is notably coarse-grained. Ruby crystals are also found in a white dolomitic granular limestone. Mining, as attested by Gübelin in Gems & Gemology, 18(3) 123–29, 1982, is primitive. Bowersox in Gems & Gemology, 21(4) 192–204, 1985, notes that he most noticeable inclusions seem to be small spots or zones of a strong blue colour; their shape is mostly trigonal or hexagonal in outline. Some stones show parallel blue bands. A sharp division between red body colour and blue patch is highly characteristic of Jegdalek rubies. Crystals, apparently of calcite, are common.