New Mineral Named After GIA’s John Koivula
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 Post subject: A bit of a burn on tourmaline?
PostPosted: Sat Apr 20, 2019 6:19 pm 
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I would like to share some of my speculations about an interesting kind of tourmaline. Its core is a slightly bluish gray core while its surface is a bright pink colored skin. I first ran into this material when I was searching for tourmaline that was blue/purple. I had not been active when the original Paraiba had come on the market and I despaired that I would never fined a medium toned bright blue/purple tourmaline. I consider that color range to be the scariest in the color world of tourmaline. The discovery of cuprian tourmaline in Mozambique changed the color balance in my world with beautiful blue purples and satisfied my need..

The first piece of note, I purchased from Africa was a large crystal that had most of its skin removed in an attempt to improve its clarity rating. The rough had been billed as blue purple and perhaps the mixing of the cores slightly bluish grey and the remaining skin produced such an appearance to someone. The skin was too thin to be retained in the finished stones which turn out to be a medium grey. Now this was frustrating, but getting to see the skin on the rough was very interesting. The bright pink color ended abruptly and was uniform, in tone value, but it did not appear to be an added layer on to the core of the crystal. To me it looked like something has changed the color of the surface by irradiation. I came to call it burned.

The next specimen with the bright burned skin as an exceptional piece of rough. I had passed on it the first time it was offered on the inter net. It was billed as a blue purple again and I suspected that it was the same material as the big crystal I had just finished cutting three grey gems out of. The dealer contacted me, since he knew that I like unusual tourmaline and after having a good back story I bought the rough. It was not expensive and was said to look like a lower grade iolite.

The rough alluvial pebble that I received had been ground extensively to get rid of surface flaws, but there it was, the residual skin that was a bright pink. As I preformed the still included rough into an oval, I noticed an interesting feature. A plum of the bright pink that extended into the heart of the gem to be. Under my loop the plum appeared to be formed by multiple exposures to some form of radioactive energy. ( sort of like in a cloud chamber)

I retained the plum in the finished oval and it just sort of blended in to the first reverse alexandrite color changer that I have come to call Laurellite. Yes the bluish grey core turned lavender when I took it for a walk under natural light. Bright pink areas in cuprian tourmaline have been noted before and the GIA also noted it in my gem, but I have never seen anything on the skin thing. I don't think that is formed in the usual way that colorless tourmaline is irradiated to pink/red after it has crystallized. The demarcation between the pink and grey is too sharp.

I got back into thinking about this type of tourmaline rough because I just finished a small emerald cut from material I purchased years ago. The bright pink skin is there, but I did no think I could incorporate any of it in the gem. Even though I really tried. Well I was right, the finished emerald cut is a rather pale grey with just a touch of blue.

My spectrometer stands ready to see what my old eyes can not and I put the stone to the test. The absorption graph did not show any indications of the higher oxidation state of manganese associated with red/pink tourmaline. Just a tiny bump that indicates iron protruded above the grey line. This confirms that the form radiation that occurred naturally was not gamma, but probably beta in my mind. Gamma goes thew thick layers of matter easily since it an electromagnetic wave while beta is electrons that do not penetrate matter very well. The interaction with beta radiation would also help explain why the line between the impacted shin and the body is so sharp.

For a phenomenon that has ha basically no impact on my finished gems its been an interesting trip.

Bruce


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Sun Apr 21, 2019 2:54 am 
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Hm, did you get a chance to take pictures of the rough and the plume of colour? It would be interesting to see how applicable beta radiation exposure is to the formation of pink tourmaline.

I currently have a (very) included grey tourmaline with a hot pink core, and a bluish gem that was cut from a lavender crystal that had hot pink marks from other crystals growing next to it.

Both had uniform colour in the pink areas, I wonder if they match your description of the rough you encountered?
While it could just be a change in pH during pegmatite formation, radioactivity from contaminates and other gems sounds like an interesting colour origin.


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Sun Apr 21, 2019 9:55 am 
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Thank you for your constructive comments. I don't have pictures of the skins and frankly they did not show up in the pictures on the inter net when I bought the material. I use my loop to see the details of the skin and I am not a position to even ask that my friend, who took all my pictures on my website, to attempt to take the pictures. I don't know if the GIA took pictures of the plum. It doesn't show up in the pictures published in their magazine. It was enough to report on the discovery of a new variety of gem quality tourmaline from Mozambique, that contained copper as a chromophore. You could certainly be correct that there is some other cause for the coloration. I don't expect any interest in doing research unless there is an trade related economic imperative. If you have pictures that could be posted, I would certainly try and give you an opinion on their similarity to my material which is quit distinctive.

Bruce


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Tue Apr 23, 2019 12:07 am 
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Here's an Imgur album of my tourmaline, sorry for the small picture of the rough, I didn't have access to this camera before I cut it and had to use the seller's image from Ebay.

https://imgur.com/a/ffBIvrt
Image


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Tue Apr 23, 2019 1:26 am 
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I have one somewhere, which is grey violet with a neon pink rind. It is etched so there is a big cavity, with the pink lining the cavity. Perhaps that is a simpler explanation for the irregular shape of the zoning.

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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Tue Apr 23, 2019 10:38 am 
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The piece that I just cut was from a complete crystal with striations on all sizes. The edges of the crystal were completely pink while the sides were just brushed with pink. I tried to get very close to the side of the crystal and accept the flaws in the skin, but as I have said my spectrometer did not see any manganese in the finished stone. The area between the core and the colored surface of the crystal must have been very thin. Maybe your hole in the tourmaline was the result of chemically eroding out a radioactive impurity? I find the pink to be quite distinctive.

Bruce


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Tue Apr 23, 2019 9:45 pm 
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Speaking of purple Paraiba Tourmaline, I just got a nice lot in today. Most is the really intense purple color as shown in attached image. Some has a strong blue component as well. Should cook very nicely. Clean stones just over 100 grams total, ranging from about 5 grams up to this one at 23.7 grams. This is the second parcel like tis I have picked up recently. Apparently good production coming out right now.

Sorry for the blurry cell phone camera picture.


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Pariaba23.7gms.jpg
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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Wed Apr 24, 2019 7:03 am 
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Blurred or not that looks like quite a piece of tourmaline. Do you know where it came from. The GIA has reported on the finding of cut cuprian LIDDICOATITE in the trade from an unknown source. I think they are planning to publish on the different colors of liddicoatite. They tested some of my tourmaline a year ago . I thought that my non cuprian purples might have come from Madagascar, where liddicoatite is reasonably common, at least in the past. I know from past testing that I have a orangest red one, but they had that color so the only new "color" was an achroite.

It is nice to see that new material is coming on to the market. There was that big fight over the name, but I think that the Mozambique find helped cement a place for Paraiba as the new "precious" colored gemstone. Without it, I don't think there was enough material from Brazil to be more than a collectors stone. With more beautiful material the trade will continue to generate demand for not only paraiba/cuprian tourmaline, but all kinds of tourmaline. (I hope).

Bruce


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Wed Apr 24, 2019 9:24 am 
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Yes, sorry I forgot to include the origin in the original post. These are alluvial pebbles from Mozambique.


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Wed Apr 24, 2019 9:40 am 
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I'll admit it, Steve, I'm impressed :D

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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Wed Apr 24, 2019 10:39 am 
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Thanks Stephen. They should heat to top Cyan color. I always feel lucky when I am blessed with exceptional rough like this parcel. I put stuff like this into the safe and hold for times when it is not available on the market, or I get a call for something special in his type of stone.


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Wed Apr 24, 2019 10:53 am 
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Back to the topic that Bruce originally posted about.

Last year I had a nice piece of water worn, pebble shaped Paraiba from Mozambique. It had a Cyan/Greenish body color, but a bright pink spot in the center that was the same shape as the pebble and took up about 20% of the very center of the stone in all directions. Imagine a pink ball wrapped in a blue/green ball. After cutting it was an interesting effect, but when turning the stone the blended colors tended to muddy the the stone color. I heated the stone, and the pink went away entirely leaving a nice Aqua/Cyan blue stone, but just a shade too pale to my tastes. I wish I had taken some pictures to show the before/after to post on the thread.

Hopefully, some may one day find it useful to know that you may be able to remove the pink, and maintain the other color if they encounter such a piece of rough. Although I also think some collectors might also object to this treatment of an unusual specimen.


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Wed Apr 24, 2019 11:06 am 
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I'd love to see that glorious purple left unheated. :smt055


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 Post subject: Re: A bit of a burn on tourmaline?
PostPosted: Wed Apr 24, 2019 11:36 am 
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Barbra Voltaire wrote:
I'd love to see that glorious purple left unheated. :smt055


The problem with that in this piece is that it is too dark in it's current state. The darker it starts, the better Cyan it ends up. There are a couple of pieces in the lot that might look nice left purple. The good news is you generally heat after cutting so you can decide then. The bad news is that the Cyan brings a lot more money in the market.


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