A diamond has been discovered that changes colour, when exposed to extremely cold temperatures. At -196 degrees centigrade, the temperature at which nitrogen liquid boils, it is known as a “cryogenic diamond,” and it changes colour from grey to yellow. According to New Scientist, this was discovered by researcher Stephanie Persaud of the Gemological Institute of America (GIA) in Carlsbad, California, while evaluating some diamonds.
In laboratories, cooling is used to make the atoms in a diamond vibrate less, allowing for more accurate measurements of the gem’s ability to absorb different wavelengths of light. Cooling is also used to make the atoms in a diamond vibrate less, allowing for more accurate measurements of the gem’s ability to absorb different wavelengths of light.
A specific section of the visual spectrum is retained by each object, including the diamonds, when it is struck by a ray of light, and this is what determines each object’s colour. By reflecting all colours, the observer perceives a substance to be completely white. When only a portion of the spectrum is retained, the colour due to trace minerals and, consequently, to its chemical composition is visible. To give you an example, chromium contributes to the ruby’s brilliant red colour. According to gemological terminology, nitrogen is the most common chromophore agent, or “chromophore agent.”
However, this isn’t the first known gem to change colour: the so-called “chameleon diamonds,” discovered in 1866 by the merchant Georges Halphen of Paris, change their hue from greenish to brown or yellow when heated to approximately 200 degrees Celsius or exposed to darkness for a period of more than 24 hours. The reason for this is currently unknown. However, given that colour variation in diamonds can be caused by a variety of physical factors, including exposure to light, heat, and even cold, as has recently been discovered, it is possible that more than one mechanism is at work to explain how they change colour.