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The value of Chameleon diamonds is decided by its unique colour-changing properties, as opposed to the diamond's colour intensity or saturation. The colour scale for these diamonds is divided into two segments. The first segment consists of the more affordable chameleon diamonds. These stones feature a noticeable brown hue that some refer to as a muddy look. Stones in this grouping are usually poorer in clarity and lustre. The second, more expensive segment, features stones which display an olive hue. These diamonds show more brilliance and lustre. A large chameleon stone is extremely rare and its price can reach six figures per carat.
Chameleon diamonds are one of the great mysteries of the diamond world. It is still not known why these diamonds change from deep green to yellow when heated or left in darkness. This unusual quality makes chameleons among the most fascinating of natural coloured diamonds. Despite the lack of knowledge about why these diamonds change colour, the GIA and other highly reputable gemmological laboratories have acknowledged the existence of two basic types of chameleon diamonds. Chameleon diamonds are graded as classic or reverse. Most chameleon diamonds are classic, with a stable body coloured greenish grey to greyish greenish yellow (olive) with brown or yellow undertones. When subjected to heat of more than 2000C or a minimum of about 24 hours in the dark, the stable body colour changes to an unstable body colour of yellow, orangey yellow or yellow with an olive green modifier.
Chameleon diamonds do not appear in all colour intensities. For example, they cannot be found with vivid and intense colours. Chameleon diamonds always possesses diamond fluorescence and they will always include some sort of colour combination. The combinations always include any of the following colours: Green, yellow, brown, and grey. Chameleon stones usually contain at least two overtone colours. Some of the more common overtone combinations are brownish-yellowish, grey-yellowish, greyish-yellowish, grey-greenish, brownish-greenish, and green-yellow. This phenomenon cannot be found in pure coloured diamonds.