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 Post subject: 2.5mm mounted green demantoid shows fingerprints and needle
PostPosted: Sat Jun 26, 2021 12:28 pm 
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Hi,
I recently examined a mounted piece of jewelry claiming the side stones 2.5mm round are russion demantoid but they have basically no fire(might be due to poor cut), yellowish green, with no curved horsetail like inclusions at all but with typical tsavorite fingerprints, nailheads and needles. I can not get a proper RI reading.
Is there another way to confirm these are androdite instead of glossulorite ??
without unmount the stone, of course.


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 Post subject: Re: 2.5mm mounted green demantoid shows fingerprints and nee
PostPosted: Sat Jun 26, 2021 1:51 pm 
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Always difficult with mounted stones that small.

Raman Spectrometer is my first choice.

Although Visible Spectrum is not useful for Grossularite, it should be diagnostic of Demantoid if you can get a good reading.


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 Post subject: Re: 2.5mm mounted green demantoid shows fingerprints and nee
PostPosted: Sat Jun 26, 2021 3:40 pm 
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Location: San Marcos, CA
We have seen in past parcels of Pakistani demantoid melee, exactly the same yellowish green, no life what so ever. Although these were loose stones and easy to ID as demantoid and COO was at face value.

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 Post subject: Re: 2.5mm mounted green demantoid shows fingerprints and nee
PostPosted: Sat Jun 26, 2021 10:59 pm 
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Demantoid garnets are the only green stone which can be picked up with a rare earth magnet.
I haven't tried this myself, but perhaps you could rig up a flotation device of sorts for the ring and see if you can pull it with a magnet directed at the green stones.

Hand held spectrum might shed some clues, but I'm frankly not optimistic. I have a lot of experience with an OPL and I would not rely on it for separation of demantoid vs tsavorite vs ????

Can you get a polariscope reaction to indicate single refraction?

If the jewel is antique, Russian. round, demantoids were always cut with pentagonal symmetry. That's a diagnostic slam dunk. Are there any maker's marks or hallmarks in the piece you could research?

As I've mentioned before, if there is nothing one can supply as proof of identification of an unknown, it is wise to say testing was inconclusive.

Adding, identification could not be determined within the mounting using standard gemological instruments.


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