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 Post subject: Re: Purple Garnets
PostPosted: Wed Jul 27, 2016 11:51 pm 
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Steve just posted a piece of this rough on FB, with a description that I thought was useful and enlightening:
"A very rare and beautiful variety of Garnet from Mozambique. This material displays predominately purple color in white light and shifts to an intense magenta under Halogen or Incandescent bulbs. This material will surely cut an impressive gemstone! This material is 52% Pyrope, 47% Almandine, and is a mix of other garnets for the last 1%."
The color shift sounds like what I saw at Tucson and in other fine purple rhodolites. The composition is very classic rhodolite (in the more modern commercial sense, with a larger amount of almandine than the original definition). To be fair plenty of garnets are about 50/50 almandine/pyrope, including lots of mere mundane reds (ie, Gore Mtn garnets for those familiar). There's some chromophoric magic that brings in these magenta-purple tones.
I just picked up this piece on eBay out of curiosity. Just over 10 carats, just under 20 dollars. It's a bit dark and it does have some silk, but the hue is pretty accurate in the photo and it passes the white paper test (albeit not with flying colors). No doubt Steve's stones are better but I don't think there's any sort of varietal difference, just quality.
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 Post subject: Re: Purple Garnets
PostPosted: Thu Sep 08, 2016 4:10 am 
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Purple Garnet handmade bracelet


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 Post subject: Re: Purple Garnets
PostPosted: Thu Sep 08, 2016 9:53 am 
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Tiny image!
From what I can see it almost looks as if it could be from the Butuglia designer line.


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 Post subject: Re: Purple Garnets
PostPosted: Thu Oct 12, 2017 3:53 am 
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Hello everybody.
i read with a great interest what have been written about heat garnet, last year.
Quote:
Some pyrope-almandine garnets found in the U.S. have been named after the Greek god who it was believed could change shape and form. The treatment, presumably by heat, brings a thin layer of metal, probably iron, to the surface of the stone that resembles hematite. They show a dark gray metallic luster in reflected light while glowing dark red in transmitted light.

I think it’s reasonable to assume similar garnets can be found worldwide.


I have some old garnets, and i beleive they've been treat by heat. Actually garnets have irregulars layers and beetween them I got the oxyde layer, indeed. It also shows a lot of inclusions . Do it may be the result of heat ? Can you advice a book or article talking avbout he effect of heat on garnet ?

Many thanks in advance


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 Post subject: Re: Purple Garnets
PostPosted: Fri Oct 13, 2017 6:05 am 
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It is possible. I have a big bag of garnets this treatment was done on and it is a very complete, distinct metallic coating. It would be a pointless treatment, except that ALL the sirfaces develop it, even internal fractures, so some of the garnets are suddenly filled with reflective silver foil. If cabbed properly they can be stunning.


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 Post subject: Re: Purple Garnets
PostPosted: Fri Oct 13, 2017 2:54 pm 
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Thanks for your reply. But acyually I'm afraid i didn't explain my point very clearly.......
i m interested by the aspect of the garnet on the photo. so much cristal that it seams "agregat".... this may be the result of heat ? The heat may show up the impurities in the cristal till this point ?
Im not specialist at all....
Mah be it is not a garnet ? Color and density are ok. But binocular shows this irregular shape.....


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 Post subject: Re: Purple Garnets
PostPosted: Fri Oct 13, 2017 7:39 pm 
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Oh, I see what you're asking. This is a typical feature of garnets that have experienced stress (which is common since they often form in metamorphic rocks). Garnets tend to break into squarish platy segments so you get this sort of look.


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 Post subject: Re: Purple Garnets
PostPosted: Sat Oct 14, 2017 2:47 am 
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Indeed on early midfle age people were using these plates for cloisonné jewellery.
And actually most of plates were thin less than 2mm, perfectly polish and transparents almandines.
On his post Rick Martin said that layer of oxyde may occure on pyrope slmandin. Can i found any article or reference to read about ?
Stephen the garnet on the photo can be like that naturally so ? It sound logic, it may need high pressure and heat to get this result....
If you can advice anything to read and learn about i will higly appreciate.....
Many thanks
Have a nice day


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 Post subject: Re: Purple Garnets
PostPosted: Sat Oct 14, 2017 4:28 pm 
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My long-ago post was about a pyrope-almandine garnet found in Idaho that, when heated, displayed a metallic coating similar to marcasite or hematite. It was marketed under the name of Proteus. Stephen mentioned owning some of it upthread. I see no reason why garnets with similar properties might not be found worldwide.

Here's a link where it's mentioned:
https://www.gemsociety.org/article/proteus-garnet/

However the suggestion that cloissone was made from such garnets makes me wonder if there might be confusion with the Saxon garnet cloissone technique in the Middle Ages. The Stafforshire and Sutton Hoo hoards in the U.K. are fine examples of how polished thin sections of pyrope-almandine were inlaid in cells above a reflective gold backing that was sometimes engraved. The garnets used were not heated nor did they have a metal coating. For examples see: https://www.google.com/search?q=sutton+ ... 97&bih=480

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 Post subject: Re: Purple Garnets
PostPosted: Sun Oct 15, 2017 1:58 am 
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Yes and it was local garnet. As Gamla in Sweeden.
https://zellwerk.hypotheses.org/tag/sweden

But European cloisonné were definitly done with indian almandine as demostrated with XFR and PIXE.
They even identificate the quarries...
http://www.academia.edu/7244613/Provena ... _by_PIXE...
but not all garnets can but cut that way.
I'm trying to found an bibiographic reference concerning the geological reason of this metallic layer.
Im also trying to understand why the garnet on my photo get so many cristals inclusions.....
Thanks to you.


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