From Gray to Yellow at -320F: Introducing the Color-Changing Cryogenic Diamond
October 10, 21
(IDEX Online) - Newly discovered "cryogenic" diamonds change color from gray to yellow at extremely low temperatures, say experts at the GIA lab.
They're the opposite of "chameleon" diamonds, first discovered in 1866, which change color at very high temperatures.
Stephanie Persaud, senor analytic technician at the Gemological Institute of America (GIA) in New York, made the discovery by chilling a diamond to -320F/-196C, the temperature of liquid nitrogen.
The rarity of chameleon diamonds has made them extremely valuable. Cryogenic diamonds may now become the next big thing for collectors.
Paul Johnson at the GIA's Department of Research and Development told New Scientist: "Consumers love rarity, that is what brings value to a diamond."
He believes an explanation may be that the electric charge moves closer or further away from impurities in the crystal at very low temperatures, making the diamond and appear differently when impacted by the light.
His team has so far discovered five examples of the cryogenic diamond (including the 3.8-ct diamond shown).
Chameleon diamonds change from grayish yellowish green or grayish greenish yellow to an intense brownish or orangy yellow to yellow color when heated to 302F/150C. Scientists still don't understand why.