FANCY COLOR DIAMONDS

THE MYSTERY OF THE CHAMELEON DIAMOND

There is a sliding scale in terms of fancy color diamond rarity, with pale and grayish yellows and browns relatively commonplace, but vivid yellow, pink, blue and green exceedingly rare. Even more infrequently seen colors are reds and purples. But there is a type of fancy color diamonds that is in a class of its own, and what makes them particularly interesting is that it is inherently impossible to properly define their color.

Meet the chameleon diamonds, which owe their designation to the fact that change color, although, unlike their reptilian namesakes, not according to the branch or leaf on which they are standing.

The factors that govern their appearance are temperature and light, or the lack thereof. Under regular conditions, they typically are grayish yellowish green to grayish greenish yellow in color. But, when if heated to 150 degrees Celsius (302 degrees Fahrenheit),  exposed to light after being kept in the dark for a prolonged period, they temporarily become an intense brownish or orangey yellow to yellow color.

FIRST CHAMELEON RECORDED FOR MORE THAN 150 YEARS BACK

According to the Gemological Institute of America, the first recorded evidence of a color-changing diamond was 1866, when such a stone was reported by one Georges Halphen, a dealer in Paris.

The first time the term chameleon diamond was used to describe these color-change diamonds in the jewelry trade was in 1943.

The GIA website tells the story of a person who purchased light yellow green diamond in the early 1970s. It was placed in a jewelry box, and when he removed it from there for the first time the buyer noticed that the diamond was now dark green, presumably a variation on the brownish or orangey color mentioned before. Confused, he returned the diamond for a refund, saying it was not what he originally purchased.

SOURCE OF CHANGING COLOR NOT CERTAIN

The reason for their color change phenomenon remains unclear, although GIA suggests that, the stones alter their appearance when exposed both to light (known as photochromism) and heat (known as thermochromism), there may be more than one mechanism at work.

Researchers have reported that such stones contain unusually high concentrations of hydrogen, as well as traces of nickel and nitrogen, and this complex mix could be responsible for the chameleon effect.

The GIA did conducted conduct as study on 29 green and color-changing diamonds to determine the differences between them. On observation was that as a green diamond that is exposed to extreme heat will permanently change colors, whereas a chameleon will always return to its original hue.

Despite the difficulty in pinpointing the chameleon diamond’s color, GIA is prepared to issue them with a Colored Diamond Grading Report, with the standard procedure being to record its visible absorption spectrum, as it is for all stones. But the GIA graders keep an eye out for  a change in color if the diamond is heated slightly or placed in the dark, and the  comment on the report of a diamond whose color changes temporarily will be “chameleon.”

If you see that, you are a member of a very exclusive club.