Pink Sapphires Can Turn Orange in Bright Light, says GIA
December 13, 22
(IDEX Online) - Pink sapphires exposed to sunlight or incandescent illumination can undergo significant and "unusual" color changes, says GIA.
They can acquire the same coloration as highly-prized padparadscha sapphires - a unique mix of pink and orange - or even turn completely orange.
The gems are routinely tested for color stability, by exposure to bright light for several hours, which causes an unstable orange component to fade, says a preliminary GIA Lab Note, An Update on Sapphires with Unstable Color.
But the authors say that in recent tests, some sapphires reacted unusually to the test by gaining orange or yellow coloration
"This color change behavior raises important questions about determining and reporting the color of sapphires exhibiting this color change," says the note.
"In GIA's experiments, the color observed after the color stability test is very similar to the color observed after exposure to daylight, for example, if set in jewelry and worn frequently."
To illustrate the color changes, GIA shows how a 3.54-ct padparadscha sapphire (pictured) increased its orange color during the color stability test. If left in the dark for an extended period, the color could become less orange or even go to straight pink.
This can be replicated by exposing the sapphire to intense LED illumination. This stone would be characterized as a padparadscha sapphire because the pink-orange color after the stability test is acceptable.
Photos by Diego Sanchez.