6ct Pentagonal Kashmir Sapphire

More than 95% of the world's sapphire are thermally enhanced but you rarely see  a heated Kashmir because the mining stopped almost 100 years ago.  

This is a 6ct pentagonal fancy shaped Kashmir after low temperature treatment. The origin is easily identified by the small spots of kaolin corrosion on the backside, the broad zoning, and the classic zircon needle as photomicrograph below (actual specimen).  Another feature with heating are intense yellow zones from the chromium reaction.

The vivid deep blue color is a remarkable achievement after 10 years of research and development by Eddie Cleveland.