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Alexandrite or Sapphire?

Is this Chrysoberyl or Corundum? The stone is Bluish Green in the Daylight and Eggplant Purple with a hint of pink in Candlelight. It weighs 12.18cts. It’s Refractive index is 1.760 and is Biaxial of 1.760 to 1.769 and 1.770 to 1.766. From my research this stone fits into the Chrysoberyl RI of 1.740-1.777 range but misses the 1.745–1.759 range for Alexandrite. It could be Corundum with the RI of 1.757-1.779 but if it’s Sapphire with the Bluish Green color shouldn’t the RI need to be 1.762 to 1.770 (+0.009 / -0.005)? I noticed that AJSGems.Com has a slightly different RI for Alexandrite of 1.746-1.763? I think this is Chrysoberyl and has the required colors for Alexandrite but slightly misses the mark on the RI for Alexandrite?
See attached photos.

Image 4 Green
Image 5 Purple
Image 6 Teal Purple

Hi Tracey.

You should make an SG (specific gravity) test on the stone. Corundum and Crysoberyll have different weight. You should also look at it through a spectroscope.



Most likely color-change natural sapphire.


Hi. Thank You for your response. I can see from your profile that you’re a Gemologist. Can you tell me what this is, it looks cloudy and like rain in the first image. The second image looks like cloudy banding? Does this look like a color change Sapphire or a Parti-Sapphire to you? Also, do you know what the RI range is when cutting a rough Alexandrite?
Milky Cloud Rain|636x424

Milky Cloud Rain

I would do the SG test to be a bit more sure. They both have a different Specific Gravity and you will be better able to make the determination from there. I believe this has been mentioned already. I look forward to seeing your results. To me it looks more like a natural color change sapphire. Noting to be sneezed at there. It’s a nice stone.
All the best,