GEMSTONES Figure A young worker carries the gemstone concen trate called ‘pay dirt’ or ‘rai’ in ‘Burmese style’ baskets (Pailin, Cambodia) ß Alan Jobbins Figure Washing gemstone concentrate in a small pond (Pailin, Cambodia) ß Alan Jobbins The colour does, to some extent, affect the mining, as the more popular and valuable colours are more sought after It should be noted, however, that some gemstones, including corundum, may have their colour changed or enhanced with heat treatment, irradiation (electrons, X-rays, etc.), or other techniques Kashmir sapphires, which are famous for their cornflower colour, are mined in Sanskar, an inhospitable mountainous area often covered by snow, northwest of the Himalayas The sapphires are found in feldspar pegmatites or in gravels derived from the pegmatites There has been intermittent mining since the 1920s; however, little is known about present mining because of the political situation there have been finds of prehistoric tools that suggest that mining has been carried out for many thousands of years Traditional methods involve digging a narrow pit or vertical shaft, just wide enough for the miner to be lowered down to dig out the layer of weathered metamorphosed crystalline limestone (marble) that contains the rubies The miner removes rock (often 2–3 m below the surface) and places it in a basket to be hauled to the surface and sorted Following the establishment of the Burma Ruby Mine Company in Victorian times, some mining techniques were modernized Water pumps were introduced to speed the washing process, and intricate channels were constructed from wooden planks, along which water was sluiced to separate the rubies from rock fragments As a result of the collapse of the market following the introduction of synthetic rubies and sapphires in the early twentieth century, the British Company failed and traditional methods were reintroduced In the 1990s new mines were established in the Mong Hsu area, about 250 km east of Mandalay Mogok Rubies The most famous rubies are the ‘pigeon blood’coloured rubies from the Mogok Stone Tract area of northern Myanmar, about 110 km north of Mandalay Documentary evidence shows that mining has been carried out since the sixteenth century, but