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 Post subject: Grey spinel
PostPosted: Fri Nov 29, 2019 11:18 pm 
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Around the Thanksgiving table last evening we had a discussion about grey spinel.
1/2 the table said it was the result of treatment. My half said it occurred naturally.

Anyone have any thoughts or links to literature on the subject.

Isn't it great to have the only "heated" words around the Thanksgiving table surround spinel treatment? 8)


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 Post subject: Re: Grey spinel
PostPosted: Sat Nov 30, 2019 12:19 am 
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I think heat is unlikely. Aside from not seeing it disclosed on any grey spinel I've seen for sale (and heat generally not being that common on spinel), the raman spectrum for my sample (an old stock american-cut stone) looked absolutely tack-sharp, while I believe heated spinels have broader peaks? That's all pretty darned indirect evidence though.
I've certainly started seeing more overtly-purple spinels offered for sale as grey, though, so I suppose the fad is real. I am not sure what to do with my sample, I should probably set it and sell it but I like it......
I'll try and remember to get a good picture of it to post.

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 Post subject: Re: Grey spinel
PostPosted: Sat Nov 30, 2019 9:06 am 
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From what I know, and from the lab results we got after submitting a few, they are natural, unheated.
The only heated spinels I've ever seen were red and from Tanzania, and I've seen only 2 in nearly 10 years. It's really uncommon treatment and the labs can tell.

Back to the greys: they are mostly from Burma and actually pure grey is really rare; most are actually bluish, greenish or purplish but so desaturated they appear grey. The rough is typically pretty large but highly fractured. The most enhancement you will encounter is oiling, to "hide" the surface reaching cracks. It's routinely done, so it's a good idea to soak the spinels into acetone for a night before you buy them (or can return them if you paid).


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