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Blue corundum fluorescence?

Hi everyone,

I have just seen an odd specimen of sapphire and need some advice.
blue Red

Blue in daylight and red under UV. Help?


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That is a dramatic change and a beautiful red color. I have seen natural sapphire with red fluorescence under LW uv light. SW uv light might fluoresce yellowish green. Chalky blue or yellowish green could indicate heat treatment. But the red is natural.

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Jpe206, thanks for the input. This was the only specimen I’ve ever seen transition so strongly, so I wasn’t sure what that might mean. Thank goodness it’s probably natural!

That is what we call, a critter of another world. Is it a color change Sapphire on steroids? Is it an Alexandrite gone wild? I must say that it is unique and beautiful. I would love to see more of those stones and where did that on come from?
All the best.


Hi Otter,

It only fluoresces under UV, though. It would be amazing if that were its daylight colour!
Origin unknown for now (found it looking through a friend’s old collection). Have sent it for expert appraisal so will keep you all updated when I find out.


Synthetic spinel

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Hello Ashmores,

I agree with most of the replies. Corundum stones(variety) are one of my favorite gemstones, and it looks like a beautiful Sapphire, very nice blue and I see some inclusions in the bottom of picture? But really can’t tell 100%? Could be so kind of treatment, if you look the bottom half looks a little pinkish under UV, and in day light the blue looks a little white inside, just looking at the picture I can’t tell if it is Natural Sapphire or synthetic? But I would say it does look like a Natural Sapphire around 4 to 6 carats? I hope it is real? Good Luck

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Thank you to everyone for your input! It’s just a tiny little 1-carat stone but I love it and really hope it’s not a synthetic.
It’s been independently appraised by two GIA-certified gemologists in NZ, and both tell me it is a sapphire. So it’s either a really good fake and these two people can’t do their job… or it’s a natural sapphire. There are silky inclusions, apparently.

Hi if there are silk/rutile inclusions then it will be natural, should be able to see these with a 10 X lens I would think, unless very small microscopic,