A week or so back I received some mid-quality heliodor rough. It was a nice golden color, and was relatively flawless internally (it had some minor inclusions). I intended on cutting it into a “Sugarloaf cut” to practice. As I was processing my material, I noticed the golden color faded and the stones are now a very light blueish green. What caused this? Does heliodor change color easily? I have pictures from after the color change happened, but not before sadly.
I’ve only seen one piece of Heliodor cut and it was indeed yello/golden as you described above. That said, Heliodor is really in the Beryl family, and Beryl is heat sensitive… But that shouldn’t be the cause of your color change.
I did find this quote on-line: “Originally the term “Heliodor” was coined as a trade name for greenish yellow Beryls from Namibia. Today it is widely used to describe all yellow or greenish yellow Beryls.”