Sri Lanka Ruby (Ceylon Ruby): Gemstone Information
Corundum with a wide range of colours is found in south-west Sri Lanka. Sri Lanka ruby inclines to pink rather than crimson but stones are very bright and lively – this applies also to blue sapphire. Star rubies and blue sapphires can be very beautiful. Fine examples include the Rosser Reeves star ruby of 138.7 ct (Smithsonian Institution) and the 392 ct star sapphire owned by the State Gem Corporation of Sri Lanka is exceptional. Mining is simple and any method of reaching the illam (gem gravels, perhaps 15 m down) is used, sites being chosen by chance finds of pebbles at the surface.
Virtually all Sri Lankan gems are cut and polished locally. Much blue sapphire shows the best or only blue in one part of the crystal; lapidaries manage to place the blue in the culet (bottom) area of the faceted stone so that the blue shows through the table though not in any other direction – such stones are intriguing and beautiful. Colour change (blue to purple) may be seen in some sapphires. Sri Lanka ruby shows inclusions distinctive enough for the location to be determined. Flakes of ‘biotite’ (this name is now taken as a series name for dark lithium-free mica rather than as an individual species name) are very characteristic and rutile needles are generally longer and more slender than those seen in Myanmar stones. Grains of metamict zircon are accompanied by dark tension haloes and liquid inclusions form feather-like patterns. Sri Lankan blue sapphire shows distinctive ‘arrowheads’ of rutile which form V-shaped structures; the feldspar group mineral albite, apatite and hematite may also be found. Gübelin and Koivula (1992) illustrate albite crystals forming ‘comet-tails’ (an assemblage more familiar in synthetic corundum).
Sri Lankan blue sapphires on the market today may very well have begun life as milky and colourless. The name geuda has been used for both the colourless material and the blue crystals resulting when it is heated. The treatment of gemstones for colour improvement is a major concern in the gem trade today, difficulties arising as much over disclosure as identification.