New Mineral Named After GIA’s John Koivula
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 Post subject: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 4:23 pm 
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Hi everyone, I've been a lurker for awhile, am a gemology student, and live my life putting the cart before the horse, so without further adieu

Here is a parcel of "Spinel" purchased in Afghanistan. Cuts are obviously low commercial grade / native, with terrible windowing on almost every stone (but I swear I'm learning!). Bought a parcel of various colors, sold as "Spinel".

I want to hear your opinions before I share my best guess. My questions:
Species?
Worth more/less/same than price paid?
Keep or trade for something else?


Sold as: Spinel
Price: $40/ct
Color: Pinkish red; Purplish red
Clarity: Some inclusions visible under 10x, not easily seen with naked eye
RI: 1.62, 1.64 when rotated 90° (confirmation of birefringence?)
SG: not tested
SR/DR: DR
Spectral: appears to be absorption between 490 - 530
SW/LW Fluorescence: None

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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 4:45 pm 
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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 4:45 pm 
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As a gemology student you should have access to some text books which list refractive indices of various gems.
Spinel does not have an RI of 1.62-1.64
Spinel has no birefringence, it is singly refractive.

Whatever you purchased in Afghanistan, it is not spinel.


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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 4:46 pm 
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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 4:53 pm 
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Hi Barbra,
Thanks for the reply. I expected my quotations around Spinel indicated that I was aware that it is most certainly not spinel. I was hoping for opinions of the identity based on the data provided, to cross-check my own suspicions of the actual identity.


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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 4:59 pm 
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Well, what is YOUR opinion?
It appears that you may have purchased tourmaline for $40/carat.....


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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 5:15 pm 
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Tourmaline is what I suspect. Aside from the windowing, they're quite pretty.

I suppose they're worth about half of what similarly colored spinel would be?


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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 5:20 pm 
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Right now, I'd value them at $40/carat. :wink:


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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 8:37 pm 
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Use an lcd screen to test dichroism, tourmaline usually displays it prominently.

A bit overpriced if tourmaline, given the windows. I have bought larger selected tourmalines (2-5ct) for about 40/c. These are commercial grade goods, not ones to hold on to imo. Still, there are worse ways to spend 40/ct.

These might almost be better set backwards to act like rose cuts, they look a bit dead from the front.

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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Thu Sep 19, 2019 11:43 pm 
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Hi Steve, they do exhibit dichroism. The dead appearance is more thanks to my lack of photography skill than the gems. They have a lot of brilliance around the edges but are a bit dead in the centers from the windows.

I have the option of returning them. As a beginner I'm still learning about color and cut (and everything else) so these fall below what I would buy in the future (the nature of development).

They're still interesting to me as reference samples of the material. The pics aren't entirely accurate, but would you consider this rubellite? I understand this to be among the more valuable tourmaline colors (not considering paraiba).

I appreciate your assessment of value. Some are not worth it at 40 and others a good deal at 400...its a lot to learn but endlessly interesting.

I'll have to make an intro post with some of the other material I have. Everything else seems to be what was sold...but these were clearly not spinels after checking RI, and although my non-expert conclusion was tourmaline, I wanted to rule out some unknown synthetic etc. that might get suggested.


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