December 14-16—SAN DIEGO, CALIFORNIA: Wholesale and retail show; Gem Faire Inc.; Scottish Rite Center, 1895 Camino del Rio S; Fri. 12-6, Sat. 10-6, Sun. 10-5
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 Post subject: Would like thoughts on this synthetic/simulant
PostPosted: Tue Oct 23, 2018 1:10 pm 
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Hi
My wife makes some jewellery for herself and I enjoy sourcing her gem requirements. Today I got an 'Aquamarine' from India, with (as advertised) an AGSL certificate, but that turns out to be Authentic Gem Security Lab. Alarm bells ringing I checked the stone, but nothing was obviously amiss until I tried UV light. Two frequencies, two colours, pinkish with 395nm and yellow with 365nm. I'm no expert with a microscope but I've tried most hand held instruments and RI 1.5 exactly. My Presidium gem tester sits between panels so no help at all. Dichroscope shows no pleochroism. Specific gravity is in an overlap zone.

My guess is adulterated glass, but can anyone give me a definite answer, please? :?

d


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 Post subject: Re: Would like thoughts on this synthetic/simulant
PostPosted: Tue Oct 23, 2018 2:15 pm 
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It appears that you may have wanted to attach a photo which was lost.
Could be glass, but the fluorescence suggests synthetic flame fusion spinel.
This was often used as an imitation birthstone because it can be created in every color imaginable quite inexpensively.

Singly refractive.
But the RI is off considerably.

Post a photo and tell us precisely the instruments you are using for identification


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 Post subject: Re: Would like thoughts on this synthetic/simulant
PostPosted: Tue Oct 23, 2018 3:16 pm 
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Thank you for the quick reply.
I've been doing some comparative testing with stones from reputable suppliers and though I can't get better results for the RI or get the reading high enough on the Presidium gem tester, I do have near identical results using two different types of dichroscope and more importantly, I think I've found the reason for the UV anomalies. I can replicate the result on 4 stones when using a particular piece of grey felt, which I normally use in the photo cube that I use for my turned wood items. Using a piece of grey wool felt, only the outer crown facets show any pink (minor) and there is no colour change with the lower frequency UV.
One piece of felt banished and one embarrassed old man :oops:


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 Post subject: Re: Would like thoughts on this synthetic/simulant
PostPosted: Tue Oct 23, 2018 9:29 pm 
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Well, test UV without the felt and see what happens.
Report back.


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 Post subject: Re: Would like thoughts on this synthetic/simulant
PostPosted: Tue Oct 23, 2018 10:08 pm 
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Screams like glass to me.
There's plenty of fake "certificates" around from bogus labs. Hell, there's even forgeries of real lab reports (AIGS was a victim of it not too long ago).


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 Post subject: Re: Would like thoughts on this synthetic/simulant
PostPosted: Tue Oct 23, 2018 11:19 pm 
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Yep, the RI and dicroscope (non) reaction sure sound glassy.
I have heard a lot of stories over the years of imitation and synthetic stones being copied to match lab reports.
I've also seen a lot of misidentified Verneuil synthetic spinel, usually in birthstone jewelry. Their UV reaction is diagnostic.


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 Post subject: Re: Would like thoughts on this synthetic/simulant
PostPosted: Wed Oct 24, 2018 9:52 am 
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I'm grateful for the replies and I have found some stones, which were not the genuine article, in the past. One was a glass 'Topaz' another was a synthetic ruby described as red Topaz. Even shell pearls passed off as genuine! My knowledge isn't great, but some dealers are really treating customers as fools.

Back to the Aquamarine, which I'm happy to accept as genuine on the balance of probability, because the comparative results are the same more often than different. I've tried the UV testing in a stainless steel stone holder and with mat black tipped tweezers and I get identical comparative results.

My biggest concern is for the times when I have nothing to compare to. We only have 50 or so faceted stones and rather a lot of semiprecious beads, another area where the cheats are rife, but possibly easier to spot and with prices low enough to write off the odd string, but if they look nice my Wife is generally happy to wear them.

I recently read an article about someone who wants to call synthetics, which are chemically identical to the real gem,
cultured gems. At least it might save time if the term was widely adopted and some unscrupulous dealers declared it instead of trying to pull the wool over customers eyes.


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