To achieve the colour of red tigers eye the more familiar brown and yellow coloured stone is heated. Black tigers eye produced in the same way. Whilst red tigers eye loses any chatoyance that may be present after having been heated, in the black variety it can still be seen. We believe this is because of the temperature used to bring about the respective changes in colour.
Heat treatments are not uncommon and have been widely used for thousands of years to enhance or change the colour of gemstones. The ancient Greek philosopher Theophrastus [c.371 - c.287 BC] wrote in depth about the effect heat had on different rocks and minerals. Most of the world's finest rubies and sapphires have been heated and those which have not are considered to be exceptionally rare.
This beautifully polished cabochon gemstone makes an outstanding ladies pendant but has been reduced because there is an indentation on the back of stone. This came about when the stone was polished down to remove some undesirable markings.