The gemologists at IGI Shanghai have provided images and information regarding one of nature’s rare and stunning wonders:
When at room temperature the diamond looks like this.
But… When heated to a high temperature its color changes to this.
You can see that its color is transformed by heat from a slightly grayish yellow-green to a rich yellow. This is a “chameleon” diamond, recently submitted to IGI Shanghai for examination.
Hot and Cold
While conventional color-changing stones such as alexandrite show different body color according to the ambient lighting, the chameleon diamond changes color when the temperature is different, or after being left in darkness for a period of time.
Be cautious when having your chameleon perform tricks, though: Diamond is the hardest gemstone in nature so it’s very difficult to leave scratches on the surface, but the carbon composition of diamond leads to intolerance of high temperatures. The flame of a jeweler’s torch, friction temperature from a diamond sanding disc or even a handheld lighter can potentially lead to surface burns.
No worries, friends. The diamond pictured above isn’t our chameleon – this is simply a word to the wise.
With the consent of the client, IGI thought it would be interesting to share technical data about this lovely chameleon.
This diamond weighs 2.05 carats and, when viewed under 10x magnification, shows slight internal cloudiness resulting in a clarity grade of VVS2. The color is a slightly grayish yellow-green at room temperature but under heated conditions, usually between 100-140 degrees, it changes body color to a a rich yellow color. After the temperature of the diamond drops, the body color returns to room temperature appearance again.
The documented IGI color grade for this chameleon diamond is, therefore, Fancy Greyish Yellowish Green.
The diamond fluoresced strong yellow under 365nm long-wave ultraviolet (UV) and faint yellow under 254nm short-wave UV. This also resulted in phosphorescence which remained present for about 20 seconds after the fluorescent light was turned off.
Using infrared (IR) spectrometer detection, absorption peaks appeared at 1282 cm-1 (A center) and 1175 cm-1 (B center). The intensity of the 1282 cm-1 absorption peak was significantly higher than the 1175 absorption peak, implying the diamond is Type Ia (A>B). In addition, there is a clear absorption at 3107, which is a hydrocarbon peak, representing a triple nitrogen, hydrogen and hole defect (N3V-H) in the diamond.
With the photoluminescence spectrometer, using a 514nm light source, characteristic excitation peaks can be observed at 590 nm and 701 nm, accompanied by vibration peaks at 716nm.
Using a 633nm light source, characteristic excitation peaks can be seen at 701nm and 794nm.
Conclusion: Classic Chameleon
Given the long- and short-wave UV fluorescence effects, as well as the characteristics according to the IR spectrometer and photoluminescence spectrometer, this diamond’s makeup is quite consistent with the laboratory’s previous studies of “classic” chameleon diamonds.
Therefore, in the remarks of the IGI certificate, a special paragraph has been added:
This stone may temporarily change color when gently heated, or when left in darkness for a while, referred as “CHAMELEON” diamond”, thus informing that this diamond has the ability to change color under certain conditions and is known in the market as a “chameleon” diamond.
These natural wonders can occasionally be seen in jewelry. The ring below, created by Chopard, features a 31.32 carat oval-cut chameleon diamond as its centerpiece.