(photo courtesy of Roy W. Macdonald FGA DGA)
The rarity of colour diamonds has become a popular topic on blogs like these and others. Only 1 in 10,000 carats of diamonds found can be considered colour diamonds which is why their value continues to go up year over year. The one class of colour diamonds that are among the most rare are called chameleon diamonds.
Put simply, a chameleon diamond is a diamond that changes colour temporarily when they are either heated to at least 150 degrees celsius (a process called thermochromism) or left in the dark for a couple of days (a process called photochromism).
In its original form, a chameleon diamond usually ranges in colour between a grey, yellow-green or olive colour. In its changed form, most chameleon diamonds tend to look somewhere between the shades of brown and yellow. The larger the stone, the more distinct the changed colour looks.
The changed colour of a chameleon diamond after being heated does not last long but appears to have a more intense hue. The colour of the diamond after being left in the dark for a couple of days is less intense but lasts for a longer period of time.
From a scientific standpoint, it is an excess of hydrogen and a bit of nitrogen inside the stone that gives the chameleon diamond the ability to change colours.
The chameleon diamond comes in two types, classic chameleon and reverse chameleon. The two differences with the reverse chameleon is that it doesn’t change colour when heated and that the diamond is darker in its normal state and lighter when left in a dark environment.
The largest chameleon diamond ever found weighed in at 31.31 carats and is unofficially referred to as The Chopard Chameleon Diamond. The strawberry-sized stone is normally olive green in colour but evolves into a rich bronze when it changes. It was purchased in 2007 by the Swiss jewelry company Chopard. No word on its current value but considering how the value of colour diamonds continues to rise, the cost for this rarity would easily be in the six figure range per carat.