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 Post subject: Come with me and share a personal trip with a special gem.
PostPosted: Sat Mar 23, 2019 11:02 pm 
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Just a few hours ago, I finished working on a tourmaline whose history stretches back most of twenty years. I have written about it many times and it has had its substance presented in the G and G magazine. So without further ado, lets be off.

After getting back into faceting after an hiatus of many years, I soon focused on tourmaline and I especially wanted two colors vivid orange and blue purple. After I made contact with dealers in South Africa, I began to cut and collect a wonderful spread of colors, but vivid orange and blue purple eluded me. But my dealers became sensitive to my willingness to spend significant amounts of money on "different" tourmaline. This quest for color directly lead to the dealers sending me, separably, two pieces of rough that that rather changed my life. It was not like getting marred and having kids, but it was a great joy to find a new gem variety of tourmaline. The new variety, that I have come to call Laurallite, is a reverse alexandrite color changer.

After testing out the color change phenomenon with many innocent people, I was satisfied that I had something I had never heard about. On that basis I decided to spend the money and have a lab analyze my samples. After alerting the GIA in San Diego that something different was coming, things moved quickly and copper was discovered in the three tourmaline samples I had been able to acquire. It was the first public disclosure of gem quality cuprian tourmaline from Mozambique. I knew that something much bigger than just and an oddball color change variety was developing for tourmaline. It has been a great trip.

The gems were sent around the country to be analyzed and it took two years before I got them back. When they came back, the tourmaline gemstone that I just finished working on today, had been damaged. Someone had ground off the keel of my emerald cut. The small, but clearly visible cut had been made parallel to the table. The work had been done with a rather coarse lap and there was a significant amount of chipping.

I called my contact at the GIA lab and explained the situation. After the disbelief passed, the conversation broke into great emotion. I never reported the damage officially to anyone, but I have discussed it over the years with people that saw the damaged stone. I knew I could polish out the damaged area, but I worried that the stone would window unless I recut a significant part of the pavilion.

And so my treasured stone sat damaged in its box for most of twenty years. It did have its moments of glory in far off places like Japan and Switzerland, where it was sent for further analysis, but I did not have the heart to attempt to fix it. I had decided long ago that I would do the minimum to get a reasonably nice stone out of the emerald cut when I repaired it. It had to be as close as possible to the gem I saw go from blue, in my incandescent work light to lavender in daylight, so long ago.

Yesterday, at an hour too late for most daylight savings people I sat down at the machine and started polishing out the chips. I finished the work today. Constrained by wanting to recut the minimum amount of the pavilion, I left in some minor residual chips. The small keel facets are now around the critical angle and open up much quicker than they use to (probably windowing), but I will never work on the gemstone again. After most of twenty years it is time to move on. Oh and by the way have you seen any interesting tourmaline lately?

Bruce

There is much more information on this gemstone and cuprian tourmaline in general on my website BruceFryTourmaline.com. There is also a picture of how it use to look. Its number is 944.
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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Tue Mar 26, 2019 11:23 am 
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Bruce,

Keep the stories coming. They're great reading and tell a story that's not only fun, but educational for those of us that haven't been down the road you have.

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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Tue Mar 26, 2019 8:32 pm 
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Thank you, I really appreciate your enthusiasm and interest. It helps me try and get people, interested in gems, thinking about one of the most exceptional discoveries in the history of gems, Paraiba tourmaline/cuprian tourmaline/copper bearing tourmaline/paraiba type tourmaline/African Paraiba etc. I used some of the names that have a legitimate place in the market to show how complex this subject can be. A complexity that can be used to exploit people.

Bruce


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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Wed Mar 27, 2019 8:05 am 
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Bruce, this tourmaline looks very unusual on my computer monitor. Does it have purple and green dichroism???


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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Wed Mar 27, 2019 1:02 pm 
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I would guess that is the color change effect.

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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Thu Mar 28, 2019 4:12 pm 
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Welcome to the world of strange tourmaline. The presentation of the colors in the picture are from it color change nature and lighting. I don't think anyone would think it was a tourmaline without testing.

Bruce


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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Thu Mar 28, 2019 6:14 pm 
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Hmmm, I have a nice bag of dark purple cuprian tourmaline rough. I was just going to cut it and heat it one day. I will have to check it for color change, never even thought of it.


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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Thu Mar 28, 2019 7:52 pm 
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I don't think that too many people look for color change especially in tourmaline. That is why I had a dealer, who had donated material to the GIA contact them and tell them what to expect to see. I figured he had credibility while I would be sending it from out of the blue. I have been trying to get research done on the color changer for almost as long as I have had the material. Recently I donated material that would be destroyed in testing. It was not high grade material, but anything cuprian is rare. In setting up the research effort that I don't think has been published, I had a member of the lab wonder why anyone would be interested in a gemstone that appears to be, perhaps a unique example of reverse alexanderite color change in any material. Diamond is not the only wonderful gem in the world that has value and interest. (My opinion)

The latest update I have read on Mozambique and Mavuco was from a GIA team that when while it was still busy. They question the reverse nature of the color change and none of their purples, they collected, changed color in any direction. The question I really would like answered is why some purples change color and others do not. If you want an easy way to tell if your material color changes get a transparent sheet of primary yellow and put it between the stone and your light source that is similar to daylight. It should change the stones color before your eyes. It is pretty wild.

I would love to hear about your investigation and see a picture of the rough.

Bruce


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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Thu Mar 28, 2019 8:33 pm 
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1bwana1,

Just for fun (and learning), what does heating do to Tourmaline? I'm familiar with quartz, zircon, beryls and a few others, I've just never heard of heating Tourmaline.

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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Fri Mar 29, 2019 3:13 am 
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Heating produces different results depending on the material. However, there is always a risk of getting a bad color result, and cracking. It is a dark art.....

Some Cuprian Tourmaline when heated produces the neon cyan blue when heated. This is limited to certain starting colors.

Many brown stones from locations such as Nigeria can be heated to Rubellite/Pink colors.

You can sometimes lighten dark Indicolite/Blue Green stones.

Many Tourmalines can be heated all the way to near colorless and any tone in between.


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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Fri Mar 29, 2019 6:07 am 
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1bwana1,

Thanks for the heads up. I'll do some research and learn some more. I never knew that Tourmaline could be heat treated

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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Fri Mar 29, 2019 6:36 am 
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I am not a heater of any gemstone, making a more commercial color by heating tourmaline is not my interest. But I have a number of purple cuprian tourmaline, including the reverse color changers. They would all be prime targets for heating to cyan/paraiba blue. I have recently posted on GO a post about somethings I have put together about the dark art of heating tourmaline. The GIA did some research on heating different colors of cuprian tourmaline and published the results in their magazine G and G. It covered a wide range of colors, but each color was heated to the same temperature for the same length of time and I don't think that was the way commercial heating was done on Paraiba tourmaline and its sisters. I don't think that reducing Mn+3 to Mn+2 and removing the red shade from the tourmalines was the only reaction happening. This is because I was told by a world class heater that you can wash out Paraiba tourmaline by over heating even though Cu+2 has been declared to be unaffected by heating. Could iron by a chromophore in some Paraiba from the original location. Quantitative testing has NOT shown the original Paraiba to contain a significant amount of iron and that goes for a lot of the Mozambique material too.

Bruce


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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Fri Mar 29, 2019 11:00 am 
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I can confirm that overheating can reduce, or even turn cuprian tourmaline almost colorless. Guess how I know.

Stones of the same starting color and from the same location can turn or fade at different temperatures. This can break you heart, and your bank account. When cutting tourmalines of larger sizes that I know that I will be heating. I look for areas of the stone that need to be removed during preforming. I try and find a way to slice these areas rather than grind them off. This gives me a piece of that exact stone to test heating on. I start by heating to the lowest setting that I have seen good results for that type of tourmaline. Then do additional cycles of heating until I get the result I am looking for. Then I know what the best temperature for that particular stone is.

Like Bruce says, "it is a dark art".


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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Fri Mar 29, 2019 11:50 am 
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Bruce, 1bwana1,

It's been waaaay to many years since I did chemistry (and never for gemstones). While I'm darn good in my field, listening to you two is like watching two professors arguing string theory. I'm smiling like an idiot and googling my hiney off to keep up :)

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 Post subject: Re: Come with me and share a personal trip with a special ge
PostPosted: Fri Mar 29, 2019 1:05 pm 
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Thank you very much for your confirmation of what I have come to believe, that the heating of cuprian tourmaline is much more complex than heating up the material to a certain temperature and holding it that temperature for so much time. I would like to list some of the stops along the way, to my questioning the level of understanding of color in cuprian tourmaline.

1,The first paper that reported on Paraiba tourmaline's chemistry was German and stated that the copper chromophore was heat sensitive, but it based on only one piece.

2, The first paper out of the US and at least in this country, it is considered the "discovery paper" of copper being the principle chromophore in Paraiba tourmaline stated that the copper chromophore was not heat sensitive. It was based on a handful of different colors of material from Paraiba Brazil. (only source available for cuprian at the time.)

3, I read in Englishlapis that the heating of Paraiba tourmaline is complex and people who heat treat Paraiba tourmaline, each have their own process, that is kept secret.

4, I purchase a tourmaline that turns out to have a barely discernible touch of purple blue color (I call it an Achorite) yet it has a beautiful absorption curve that indicates copper. I presumed that the tourmaline has a very low concentration of copper.

5, I visited a dealer that has some rough from the original find in Paraiba Brazil. He tells me that the heater, who process the stones he had cut from the rough, called many times, asking if it was OK to heat them again. There seemed to be a real risk associated with heating outof the last little bit of grey.

6, I communicate with the heater and found out that you can wash out the color of Paraiba by over heating it. And almost all Paraiba material is heated even high quality samples, to remove a trace of grey masking the tourmaline's color.

7, I call the heater to ask some more questions and he referred me to an article in the GIA's G and G magazine. He thinks it will answer my questions. I reread the article and found a nice presentation with many colors, but the heating of the material was all done the same simple way.
Heat to a temperature, hold for the same amount of time and cool it down.

8, Many articles claim that variations in the concentration of copper in tourmaline cause both the blue and green colors. I can find nothing in the research that has been done to support this , but there is a picture in Englishlapis that shows three pieces of a crystal. It starts out grayish, then goes greenish and then blueish as the material is heated more. Something complex is going on in the heating of this material that has not being explained by science.

With the help of your insight I think I will send my cuprian Achorite to the GIA to be quantitatively tested for copper. Do you have any samples from your rough that might have been over heated and washed out? I would like to have at least a few specimens to have tested. I will also be able to look at them with my spectrometer. If so, please send me a private email and we can help science together.

Bruce


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