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Red Spinel

Actually, JSKhor is correct… I transposed.
The natural spinel has the lower RI and the flame fusion synthetic has the higher. However, the flux grown synthetic has the same RI as the natural. SO, RI may be okay as diagnostic if you get the higher value (1.725), but if you get the lower reading this does not guarantee a natural red spinel.
The best way may be to train with naturals and synthetics using spectroscope.

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Thank you for clarifying that. I’ll update our info on synthetic spinel.

While this is well outside of most gem labs, including a great many of the more advanced ones, gas spectroscopy can aid in determining natural from synthetic: synthetic stones are grown under precise repeatable conditions, including the use of inert gases to prevent contamination. The ability to detect and identify these inert gases within your stone could prove diagnostic.

Does natural and synthetic spinel have the same specific gravity?
thank you

I was thinking about the hues and tones a gem stone has - the red spinel I recently purchased is translucent and has a orange hue ( might have a little yellow too) and is a medium to dark tone.
Does this sound normal?
Thank you

Here’s the article
from Naveet Gems & Minerals.

Thank you so much I learn a lot from your reply. :+1:

Thanks JSKhor1997 for providing the link. I’ll review and make updates to our spinel info soon.
IGS Admin

I spoke to a jeweller and they think the red spinel is a garnet. If this is been tested by a presidium gem tester and the result is spinel could the presidium gem test be wrong?
Could it be a garnet?
Thank you

Yes there is lots and lots of fake Spinel in circulation. The best Spinel is from Burma, and is not heat treated. You can expect to pay somewhere between $5-10 K per carat depending on if you are buying wholesale or retail. I’ve always sent mine out to be certified as identifying colored stones can be tricky, and at these prices you don’t don’t want to take a chance.

A simple magnetic test can quickly determine if you have a pyrope garnet or a spinel. Yes, the Presidium test could be wrong. Don’t bet your money on the results that come from these type of testers.

How do you do a magnetic test?
Thank you

Get a rare earth magnet and hold it up to the stone. If the gem is attracted by the magnet, then you have garnet. If not, then spinel or perhaps ruby.

Would this procedure help determine if the stone is natural or synthetic?
Thank you very much

Check this out, it can be very helpful Gemstone Magnetism