corundum, treatments.6, heat, gems

We have been told that conservative gem traders in Sri Lanka have been reluctant to start heat treating their own geuda" corundum, fearful of the impact this would have on the market for blue and yellow sapphires mined on the island. However, the heat treatment activities of Thai op-erators using the "geuda" have al-ready placed the Sri Lankans in com-petition with themselves for these colored sapphires. A new gas oven from Japan that can be used with ei-ther a reducing flame (for blue sap-phires) or an oxidizing flame (for ru-bies and yellow/orange sapphires) could encourage heat treatment of corundum in Sri Lanlza."