Mystery of Color‑Changing Stones: What They Are and Why They Shift

Question
I inherited a pair of very old earrings set in silver. The earrings contain two large 4-5 kt round stones that appear to look like dark, beautiful amethyst, now comes the strange part, they change color from the dark purple to almost a very light blue at times, I have even seen them in between, with greens, and medium blue. No local jeweler can tell me what they are. I have no idea really if the color changing is due to light or heat, they seem to have a mind of their own, any ideas?

Thx Kathie

Answer
Hello Kathy the best thing you can do is bring the stone to a geologists or to a knowledgeable stonecutter firsthand so they can see it and see the changes... Also try calling the
GIA that's the Gemological Institute of America located in Carlsbad California.... They are the premier school for gems...
Ask them if they can help you with this and if they have any graduates near you

regards Rolfe