JOGS International Gem Show April 7-18 Tucson Expo Center
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 Post subject: A Tale of Two Tourmalines.
PostPosted: Sun Dec 31, 2017 10:36 pm 
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Joined: Thu Sep 25, 2008 10:33 am
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Location: Mars PA
I have been working with my spectrometer to get enough variety in my set up, to write more about its operation and gemstones. I have not focused on color because my eyes do not seem to be agreeing very well with what the spectrometer is indicating in some color ranges and I will be visiting the GIA lab in Carlsbad with questions later this month, before I work with color too much more. But for now I will return to a favorite subject and use just my eyes to compare the color of two tourmalines from very different worlds.

A Tale of Two Tourmaline.

I was at one of my first stops on a trip of a life time with my daughter Laura to the West Coast 10 years ago. I was to meet with an American dealer and his Afghanistan connection and look at tourmaline rough. The American was reported to have some exotic tourmaline rough in his collection/accumulation (It was uncertain whether he was willing to sell any) and the Afghanistan dealer had direct connections to a family that directly exported rough gemstones to America. It had to be interesting even if it was not too productive.

The American showed me some material, but turned out not to be interested in parting with anything interesting. While the Afghan pour out only one pile of really interesting rough. The tourmaline was well crystallized and the flashing crystals were a bright, medium tone, sea foam. The crystals were mostly longer ratio pencils that maxed out at maybe 2 grams. All the material was clean except for a small percentage of wayward souls.

As I looked threw the pile of glowing tourmaline one of the wayward souls kept catching my eye. It was stubby and lacked the crisp flawless look of most of the rest of the lot. But it really glowed much stronger than any other tourmaline in the lot. Looking closer at it, I realized that there weren't any major flaws, just a general lack of the extreme cleanliness that you can find in Afghanistan tourmaline.

The material was expensive, but I did want to buy one piece to add to the variety of tourmaline in my growing collection. And it just had to be the stubby little glower. (It really wasn't that small because it ended up cutting a nice ring sized stone.) As I made my choice, the American added that he would have bought the piece if I had not. We all smiled and I don't think he was really that disappointed with not getting the rough. He did please me with his interest, which I think was his aim. I really did not need any support in appreciating the choice's glow like qualities. I have no idea whether it really came from the same pocket as the other material or not, but it was definitely Afghanistan material.

While we were all in a good mood, I got to show off my collection. The Afghan certainly knew more about tourmaline than just material from Afghanistan. In a flash he picked out my most exception paraiba type blue green tourmaline from Mozambique. It was the only one he asked for a price on. I had to reply that it was not for sale. I think top quality cuprian tourmaline is still a good investment.

Now we have to jump forward to a year ago or so, when I purchased a large cab grade chunk of blue green tourmaline from Mozambique. The rough came from one of my regular dealers who has years of experience in the business. It was not very expensive because it was visibly included with both major flaws and scatter. Still I really liked its clean medium tone color and it was big enough (most of a hundred carats.) to give me a good chance to cut at least one ring sized stone. Yes I did not expect to get much out of it, but what I did get out of it would be beautiful. And after spending way too much effort on it, I manage to cut four reasonable clean and bright ring sized stones out of the piece. The color had turned out to be exceptional and the crystal of the tourmaline between the flaws turned out to be good.

Now the spectrometer enters the stage. It had been upgrade, but not functioning properly when it came back from the manufacturer. I spent most of a year trying to get help from both the manufacturer and friends. Without any luck I decided to pay the price and return the spectrometer to be repaired. Well, it turned out to have been a very minor adjustment problem and the spectrometer is operating very well. With spectrometer in hand I set out to retest all the interesting tourmaline in my collection. (I had my light modified to enhance blue responsiveness and it make a real difference in the absorption graphs.)

Focusing on color rather than just whether there is copper in a tourmaline or not has broadened my field of interest. With my set back in the color area, I have still been comparing tourmaline color by eye and last night I found an excellent match in tone value, color and vividness in the sea foam from Afghanistan and the blue green cut stones from the Mozambique chunk. I don't know why I did not compared them earlier, but they had such difference histories that I did not put them in the same category. And my spectrometer had told me a secret. The Mozambique tourmaline was cuprian. Yes I had fallen into a gift that was completely unexpected to both me and my supplier.

So how do the two worlds, that these tourmaline represent. really compare. The Afghan sea foam is cut in a square step cut while the Mozambique tourmaline is cut in mixed ovals, and the cut is a factor in that most wonderful of tourmaline qualities, a glow like presences. The Mozambique material is still significantly included, but with comparable crystal to the Afghanistan sea foam which is colored exclusively by iron. While I think the best paraiba type/cuprian tourmaline has a superior glow like quality to sea foam Afghan material, I think that in this case the sea foam wins out. Also they both love incandescent light and I love to see them under that old fashion light.

The following is my opinion of course, but to try and define two varieties of tourmaline with its variable and complex nature, by their chemical nature seems obvious difficult and or expensive. ( Chrome tourmaline certainly has had its problems.) For high grade material the separationby eye,maybe obvious between copper and iron colored tourmaline, but If the eye can not distinguishes at least one significant property between the two varieties in lower grades, the window of opportunity for cheating is opened wide. Cheating that will not reflect well on the trade.


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 Post subject: Re: A Tale of Two Tourmalines.
PostPosted: Sun Feb 25, 2018 4:27 am 
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Joined: Mon Jun 16, 2014 1:10 pm
Posts: 850
Would be perfect with some pics....

gemstones, precision cuts and more...

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