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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Sat Apr 27, 2019 6:36 am 
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Thanks for the question about heating Paraiba. I have recently post some opinions about the subject, but I would like to briefly list some information that I have gotten from a professional heater. I am not a heater of tourmaline.

1, Paraiba Brazil produce a wide range of colors that were universally heated to some level of tone in cyan.

2, Even Paraiba tourmaline with a top quality cyan color were heat treated to remove a slight gray mask.

3, Still not all Paraiba was heated and it is impossible to determine which were heated or not.

4, More cuprian tourmaline from Mozambique have been left unheated.

5, Having a purple cast does NOT mean the tourmaline is unheated.

6, Not all colors from any of the locations can be heated to cyan blue. Some greens etc. will heat and some won't.

7, Heating any tourmaline is risky and Paraiba is no exception, but the reward is great in many cases with cuprian tourmaline.

8, I think the flaw structure of cuprian tourmaline is being taken into more consideration with Mozambique material than it was with Paraiba Brazil material.

9, I love the unheated cuprian blue purples, but they do not have the same glow-like brightness that cyan has, unheated or heated, or its value.

10, Transcend the Paraiba mania and seek out a top quality Indicolite. I am sure you would be pleased with it. It is certainly a rare treasure that makes all of us tourmaline lovers proud.

Bruce


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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Sat Apr 27, 2019 9:47 am 
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bruce_tourm wrote:
Thanks for the question about heating Paraiba. I have recently post some opinions about the subject, but I would like to briefly list some information that I have gotten from a professional heater. I am not a heater of tourmaline.

1, Paraiba Brazil produce a wide range of colors that were universally heated to some level of tone in cyan.

2, Even Paraiba tourmaline with a top quality cyan color were heat treated to remove a slight gray mask.

3, Still not all Paraiba was heated and it is impossible to determine which were heated or not.

4, More cuprian tourmaline from Mozambique have been left unheated.

5, Having a purple cast does NOT mean the tourmaline is unheated.

6, Not all colors from any of the locations can be heated to cyan blue. Some greens etc. will heat and some won't.

7, Heating any tourmaline is risky and Paraiba is no exception, but the reward is great in many cases with cuprian tourmaline.

8, I think the flaw structure of cuprian tourmaline is being taken into more consideration with Mozambique material than it was with Paraiba Brazil material.

9, I love the unheated cuprian blue purples, but they do not have the same glow-like brightness that cyan has, unheated or heated, or its value.

10, Transcend the Paraiba mania and seek out a top quality Indicolite. I am sure you would be pleased with it. It is certainly a rare treasure that makes all of us tourmaline lovers proud.

Bruce


Thanks Bruce. This is the sort of colour I'm talking about, which I think is from the original Brazilian find:

https://www.instagram.com/p/Bmyqq6anwbR/

To me that colour is so much better than the neon cyans that are associated with this tourmaline variety.

I also collect crystals rather than cut stones as I find that minerals in their natural state so much more fascinating as each one is unique, and if they are in matrix, tells you the geological conditions in which they were formed.

I would certainly love a crystal of one of those cuprian 'reverse alexandrite' colour-change tourmalines (laurellite).

I also hope to find an excellent specimen of the vivid blue cobalt spinels from Luc Yen one day.


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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Mon Apr 29, 2019 8:12 am 
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We can be dreamers together, Nick. When I was actively buying cuprian material from Mozambique, I would write descriptions of my efforts to cut the beautiful material and fantasies. One of the stories was about the breaking up of the "mother" crystal and the years of rolling around in the river until the "children" came to rest on the deep beds of gravel next to the bed rock.. There to wait until the eyes of man discovered it.

I dreamed of the crystals that had been, but everything I could get was so water worn that you could hardly see any striations on more than one of the pebbles. I could not even supply material that could be oriented with the principle axes for further research after the discovery of copper in the Laurellites I supplied the GIA.

I would NEVER cut such a crystal specimen that I saw in the link. I have gathered from more than one source that very few gem quality specimens were saved from Brazil. I have also seen rough unheated material from the original level in the mine that really produced enough cuprian material for the Paraiba wave to start. I have sought out every thing in pictures/written about Paraiba ( I missed your picture) and highly question that that specimen came from the original source or may even be cuprian. I would want to see a copper test with a spectrometer before I would accept that crystals as copper bearing.

That said I love the specimen in a rare color for tourmaline and thanks for sharing it. I started my love of minerals with crystals and have never grown out of it.


Bruce


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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Tue Apr 30, 2019 3:16 pm 
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bruce_tourm wrote:
We can be dreamers together, Nick. When I was actively buying cuprian material from Mozambique, I would write descriptions of my efforts to cut the beautiful material and fantasies. One of the stories was about the breaking up of the "mother" crystal and the years of rolling around in the river until the "children" came to rest on the deep beds of gravel next to the bed rock.. There to wait until the eyes of man discovered it.

I dreamed of the crystals that had been, but everything I could get was so water worn that you could hardly see any striations on more than one of the pebbles. I could not even supply material that could be oriented with the principle axes for further research after the discovery of copper in the Laurellites I supplied the GIA.

I would NEVER cut such a crystal specimen that I saw in the link. I have gathered from more than one source that very few gem quality specimens were saved from Brazil. I have also seen rough unheated material from the original level in the mine that really produced enough cuprian material for the Paraiba wave to start. I have sought out every thing in pictures/written about Paraiba ( I missed your picture) and highly question that that specimen came from the original source or may even be cuprian. I would want to see a copper test with a spectrometer before I would accept that crystals as copper bearing.

That said I love the specimen in a rare color for tourmaline and thanks for sharing it. I started my love of minerals with crystals and have never grown out of it.


Bruce


Hi Bruce. That purple/violet tourmaline is from Alan Hart's Instagram feed. He used to be the curator of the Earth Sciences department of the Natural History Museum in London and is now the head of the British Gemmological Association, so he knows his stuff! The more violet and purple hues are due to manganese combining with the blues and greens of the copper apparently. Here's a relevant quote:

Quote:
The combination of the copper along with some manganese in Paraiba tourmaline gives rise to a variety of beautiful colors ranging from emerald green to mint green, neon blue to sapphire blue, to indigo and purple. Copper in high concentrations is responsible for the rare and highly-prized blue and green hues, while violet and purple colors are due to the greater presence of manganese.


^From https://geogallery.si.edu/10002897/paraiba-tourmaline (and that is a stunning blue!).

Perhaps heating the more purple specimens somehow changes the valency of the manganese thus eliminating the purple component?


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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Tue Apr 30, 2019 8:07 pm 
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It is great to see interest and added information to one of my areas of intense interest. (Though I think we have drifted from the world of beautiful spinel.)

1, I think the reduction of manganese plus 3 to manganese plus 2 is universally accept as the process by which the RED component of the cuprian purples is reduced or eliminated.
(original Rossman paper)

2, I think that copper plus 2 is the only oxidation state of copper that colors tourmaline.
(original Rossman paper)

3, I think that copper plus 2 is not changed by heating and produces a blue color in tourmaline.
(original Rossman paper)

4, I think that some cuprian tourmaline from Brazil that is greenish can be heated to blue. (Picture in Englishlapis Tourmaline issue.)

5, I think that some greenish cuprian tourmaline can not be heat treated to blue, (G and G article which included heating cuprian tourmaline)

6, I think that copper plus two is only found in the y site in the chemical make up of tourmaline.
(Original Rossman paper.)

7, I think that iron has been shown to be a coloring agent in some cuprian tourmaline. ( Article in G and G about using the spectrometer to determine chromophores in tourmaline)

8, I think that radiation induced color centers play a roll in producing the yellow vector in green cuprian tourmaline. It can be eliminated by mild heating and would not depend on a transition element. (My own speculation.)

9, The yellow component of cuprian tourmaline was postulated to be from a combination of manganese and titanium in a low iron environment, in the original Rossman paper. The postulation that different concentrations of copper produce blue to green in tourmaline was NOT supported in the original Rossman paper.

A few closing comments. I think that green color in cuprian tourmaline is much more complicated that just variations in the concentration of copper. I have seen many analysis of cuprian tourmaline, but no hard numbers that say what concentrations of copper will produce blue and which will produce green. I do not support the contention that titanium is a factor in coloring cuprian tourmaline.

Finally, I personally do NOT see how a single valence state of copper that is found in only one location in tourmaline and is not effected by heating can, by itself, introduce a yellow vector into the many tone levels of saturated blue color found in cuprian tourmaline. In other words I am asking for a chemical explanation of the effect of changing the concentration of the copper chromophore in tourmaline.

Bruce


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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Tue Apr 30, 2019 8:19 pm 
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See my comments below.


bruce_tourm wrote:
It is great to see interest and added information to one of my areas of intense interest. (Though I think we have drifted from the world of beautiful spinel.)

1, I think the reduction of manganese plus 3 to manganese plus 2 is universally accept as the process by which the RED component of the cuprian purples is reduced or eliminated.
(original Rossman paper)

It has been my experience that I can always heat out the Red/Pink from Tourmaline.

2, I think that copper plus 2 is the only oxidation state of copper that colors tourmaline.
(original Rossman paper)

3, I think that copper plus 2 is not changed by heating and produces a blue color in tourmaline.
(original Rossman paper)

4, I think that some cuprian tourmaline from Brazil that is greenish can be heated to blue. (Picture in Englishlapis Tourmaline issue.)

I have seen some bG material whose color improves to gB when heated.

5, I think that some greenish cuprian tourmaline can not be heat treated to blue, (G and G article which included heating cuprian tourmaline)

It is spotty in Brazilian material, and even less likely in African material. I no longer heat these colors because the risk if cracking exceeds the odds of a good color.

6, I think that copper plus two is only found in the y site in the chemical make up of tourmaline.
(Original Rossman paper.)

7, I think that iron has been shown to be a coloring agent in some cuprian tourmaline. ( Article in G and G about using the spectrometer to determine chromophores in tourmaline)

8, I think that radiation induced color centers play a roll in producing the yellow vector in green cuprian tourmaline. It can be eliminated by mild heating and would not depend on a transition element. (My own speculation.)

I have a large completely clean yellow/brown/green (Olive Color) Cuprian Tourmaline from Mozambique. I will one day heat in hopes of removing the brown, and reducing the yellow. I have heard that this sometimes works, making a better, but still not great color. I will report back when I do it.

9, The yellow component of cuprian tourmaline was postulated to be from a combination of manganese and titanium in a low iron environment, in the original Rossman paper. The postulation that different concentrations of copper produce blue to green in tourmaline was NOT supported in the original Rossman paper.

A few closing comments. I think that green color in cuprian tourmaline is much more complicated that just variations in the concentration of copper. I have seen many analysis of cuprian tourmaline, but no hard numbers that say what concentrations of copper will produce blue and which will produce green. I do not support the contention that titanium is a factor in coloring cuprian tourmaline.

Finally, I personally do NOT see how a single valence state of copper that is found in only one location in tourmaline and is not effected by heating can, by itself, introduce a yellow vector into the many tone levels of saturated blue color found in cuprian tourmaline. In other words I am asking for a chemical explanation of the effect of changing the concentration of the copper chromophore in tourmaline.

Bruce


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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Mon May 06, 2019 6:55 am 
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Thanks for your heated experiences and possibilities for the future.

I would like to add one more facet to the yellow side of paraiba tourmaline that might make things more complicated. Now that the discovery of the high manganese tourmaline, Tsilaisite, has been tested and accepted, it is another option for coloring paraiba tourmaline. I was just reading that samples of the new species could be considered a mixture of Elbaite mixed into areas of Tsilaisite just like the widely accepted mixing of Liddicoatite and Elbaite. (A similar structure can be found in garnet.) This means that that the paraiba/cuprian tourmaline would not have to be exceptionally high in manganese, to be yellowed by Tsilaisite. On top of this personal speculation, I don't think that you could heat out the yellow, which I think is intrinsic to Tsilaisite. I like the idea because it does not add a new transition element to the tourmaline and yet could produce a yellow color without a color center.

Isn't tourmaline wonderfully complicated and much of it is displayed in all the colors of the rainbow and more.

Bruce


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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Tue May 07, 2019 8:36 am 
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bruce_tourm wrote:
Isn't tourmaline wonderfully complicated and much of it is displayed in all the colors of the rainbow and more.

I happened to be in Madeira last week, a portugusese island as you know, and visiting a botanical garden I fell (of course !) on an exhibition about brazilian minerals and gemstones.
All brazilian gemstones were displayed, and among them, there was an impressive three-rows dedicated to tourmalines, of all possible colors.

I tried to take a panoramic picture of these tourmalines, but through the window and in a hurry the quality is terrible !


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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Mon May 13, 2019 5:07 pm 
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Thanks for the effort. Did it have any rich amethyst like tourmaline?

Bruce


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 Post subject: Re: Luc Yen cobalt blue spinel.
PostPosted: Tue May 14, 2019 11:42 am 
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I think there were some purple ones, but my memory doesn't precisely go up to the shade.


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