Gem ID Help With Pleochroism Stone

Have a fun antique ring I found. Gem ideas? It is showing three colors- blue, green, and yellow when turned in daylight. RI is 1.79 which is what’s throwing me off! My little cheap “diamond tester” puts it at a 7-7.5 hardness. There is no SW florescence. What do you think?


I think its glass.


glass is 1.52-1.55 so that doesn’t work. Other ideas?

No. Glass has a RI of 1.750-1.470 ( according to Gemmology Tools ). How accurate is your refractometer? Is the stone double or single refractive? Does it have any pleoroism?
I downloaded one of your pictures and enhanced it and when i look at the damage of the stones edges i suspect it is glass. Of course, i can be wrong. It is very hard to make an identification just by looking at a picture.

Best regards

Hello. Get an accurate RI of an assembled stone is not always possible. Try higher magnification (30x or more)…if you see air bubbles and the facets edges are no sharp it is almost certain that it is glass. And try to scratch any quartz piece (gently to avoid damaging the gem edge). If you scratch the quartz is not glass, otherwise…

With your RI reading it is quite probable you are seeing the limits of your RI fluid. Typically those are 1.79. Thus, the stone is OTL (over the limits). In this case consider the stones that have those colors and you may be looking at a zircon. Or perhaps something like a colored CZ, YAG, etc.

Does your equipment list include a polariscope? Are you getting a DR blink?
Good Luck, hope you have blue zircon.


Looks like you have color change sapphire
numbers are off with hardness…RI is close…
double check

color change sapphires examples

With my gemological microscope, it’s definitely not glass. Let me see if I can get a photo of It does have pleoroism as well.
From 1930 estate. Should I pull the stone?

Hi Bear, What should I look at with the Polariscope?

With your gem scope, did you see doubling? You can look through a face up star facet and focus down to the bottom of the stone’s keel. You will see a marked doubling image at the bottom of the stone. This is indicative for an OTL stone like zircon.

Under crossed polarizers (dark) you will get a birefringent blink as you turn the stone. This will eliminate singly refractive stones like glass, CZ, YAG.

Have yo taken any gemological courses?

StoneGroupLabs, LLC

A “close” RI doesn’t quite cut it. If it were corundum the RI would be in the 1.76-1.77, and the reading they obtained was a 1.79… right at the RI fluid maximum. Such a reading is typical of an OTL stone.

No way…really??? The RI of corundum isn’t 1.79? Oh my God…thank you so much!!!

Maybe the poster made a mistake with the reading of the RI?
Reread my reply.

Thank you. I am going to go into town and use a friend’s unit and see if that yields a different reading. This stone is frustrating me! I appreciate you taking the time to chime in.

New clues.

  • new RI fluid. 1.71
    Biaxial in conoscope
    Three colors pleo- yellow/pale green/ aqua blue
    7 or 7.5 hardness
    no sw florescence

My guess is color change Diaspore

I think you’re right, I concur its colour change diaspore😊

Have look at this and it may help.

Confident that it is a sapphirine after two more took a look.
Very exciting piece.

…that’s wonderful…very rare!

I don’t have much to add here beyond, wow. That is a beautiful stone.