AGTA TUCSON GEM AND MINERAL SHOW: FEBRUARY 4-9 2020
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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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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Sun Dec 22, 2019 8:23 pm 
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Quick update, I checked my notes and had originally bought these for $30, not $40. In the lot, 2 pieces were actually greyish spinels, 1 piece was a synthetic color-change sapphire, and the rest tourmaline.

I saw my seller again this week after several months, and he offered to let me keep these at $20/ct so I decided to retain them as specimens.

I returned 30 something carats of blue sapphire that ended up being lab created or diffused.

I also returned 10cts of Emerald that was natural, but I suspect treated with opticon/resin. They were $350/ct so I didn't expect too much and if I were confident they had only been oiled I'd have kept them. As an experiment I tried removing the oil with industrial spirit and some of the treatment came out, but inside some of the fractures was a rainbow flash effect which I presumed to be from polymer and not oil.

I also declined most of a parcel of poorly cut tourmaline (brilliant cuts) I had previously reserved, but accepted the ~30cts of rectangle cut light pinks at $40/ct (down from $65 I had previously agreed). I know that's the upper end for where you would value this quality, but they won't make me rich and won't make me poor.

I additionally returned some light bluish-green "aquamarine" that tested as tourmaline. It did react to the Chelsea filter, so is it possible it was chromium bearing?

My seller discounted 2 1-carat diamonds I had purchased last time. GIA returned them as I/SI2 and G/SI2 (in line with my expectations) but cut unfortunately was only Fair (so I asked him to discount the price and he agreed. As with the colored stones, I didn't assess the cut initially but I'm slowly learning. Final price after shipping/grading is now $1850/ea, and I feel I can now come close to breaking even in the event I sell them.

With my credit from my returns and a modest capital infusion, I've replaced the synthetic/low quality material with a GIA graded 1.31ct cushion VVS1 U-V ($2500) and a little less than 30cts of nice looking Tanzanite. I have a GIA GG graded 6/6 Tanzanite as a reference sample, and to my untrained eye I think these would be a GIA 4/4 or 5/5.

He brought me 2 very nice 6ct light pink spinels, but at $700/ct I thought they were too high. They're purported to be from Badakshan, which is the same area as where the light pink Tajikistan spinels are found. I've tried to research the value based on Tajikistan material but there's too much range in posted prices for me to infer a fair value.


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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Sun Dec 22, 2019 8:36 pm 
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Mr.H wrote:
I additionally returned some light bluish-green "aquamarine" that tested as tourmaline. It did react to the Chelsea filter, so is it possible it was chromium bearing?

If it was really tourmaline it is almost certainly worth more than an equivalent aquamarine.

Aside from that, you'd probably do better to spend your money at a larger trade show like Tucson than with a single dealer (and moreover one who either doesn't know his stuff that well or isn't always being straight with you).

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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Sun Dec 22, 2019 11:08 pm 
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Hi Stephen,
Various tests (ri, dichroscope, sg, polariscope, inclusions, etc.) indicated tourmaline. They were ~4ct oval brilliant cut but not eye clean and with windowing. Color was greenish with a slight blue modifier and light tone/saturation (The 4 green ovals from this parcel of aqua)
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Price was $65/ct from this parcel. Aqua was very clean but not much color...I thought the color of the ovals was more interesting (maybe a green beryl) so I took 1 piece to test and asked him to hold the rest. For poorly cut, lightly saturated green tourmaline it didn't seem worth it, but the Chelsea filter reaction certainly makes them interesting.


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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Sun Dec 22, 2019 11:47 pm 
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Here are the sapphires and emeralds I traded ( minus the Tsavorite in the background of the emerald pic). You can see some of the rainbow flash even in the picture on the face of the emerald on the left.
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I basically traded for the cushion diamond, peridot and the trillion tanzanite.
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The 16.5ct aqua was from the parcel in the last post. Price originally was $65/ct but I realised that was too high. He already paid the parcel owner to hold it for me, so we split the "loss" and I accepted it at $38/ct.

The tourmalines averaged about $30/ct. The photos don't capture the colors well...the larger piece is a 10ct watermelon but the color is on the very edges and very light...still cool to me.

The 2 shield tanzanites weight 11.5ct and were $310.

Maybe I'm not ahead, but I'm in much better shape than I was.


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 Post subject: Re: Help identifying these "Spinels"
PostPosted: Mon Dec 23, 2019 12:11 am 
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The tourmalines were from these parcels. I ended up not taking any from the brilliant cuts, but accepted the ones I had picked from the step cuts since he came down in price a little and had paid the parcel owner.

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There are dozens of shops throughout the various camps here, but most of them don't have quantity of higher quality material. When you build a relationship they will bring parcels of specific material from outside dealers when you ask. I'm not of liberty to visit Tucson at the moment, but perhaps what I learn here will help prepare me to identify better quality and value when I am able to go, if I decide to take a serious position in anything. There is unique opportunity here to look at a lot of different material and negotiate in a more hostile buying environment, which I think is great for learning. Whether a good deal on quality pieces can be found is still to be determined.


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