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 Post subject: Pink topaz - is it treated?
PostPosted: Mon Jul 22, 2013 4:56 pm 
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So I got offered this @$80/ct or $400/gm and something just didn't seem right, so I wanted to find out what treatments are done to pink it up, and what tests can be run to tell if it has been treated. Does this look treated??


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 Post subject: Re: Pink topaz - is it treated?
PostPosted: Mon Jul 22, 2013 5:50 pm 
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Pink is one of the natural colors that topaz can be found with. As to treatment, try the cotton swab with acetone test, then look for heat fractures around inclusions, etc. Very nice rough.

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 Post subject: Re: Pink topaz - is it treated?
PostPosted: Mon Jul 22, 2013 8:20 pm 
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It's hard to know for sure but I think the odds tilt pretty heavily in favor of treatment. This Federman article is old and there might be some new information out there, so take it for what it's worth.

http://www.modernjeweler.com/web/online/Colored-Gemstone-Gem-Profiles/Pink-Topaz/1$532

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 Post subject: Re: Pink topaz - is it treated?
PostPosted: Mon Jul 22, 2013 8:24 pm 
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That's Katlang material (from Ghundao Hill in Pakistan). Paler stones from this find are often irradiated to produce a very intense red-orange easily matching fine Brazilian imperial topaz, which unfortunately fades when exposed to sunlight (this, alas, I learned the hard way). Of course this treatment is restricted to those stones with just a hint of chromium. I do not believe that the intense pink material tends to be treated, though it's possible it might be heated to remove any brown overtones (likely the result of exposure to natural radiation in the earth) similar to Brazilian pink topaz. Pink is generally perfectly stable in topaz, since it's caused by trace amounts of chromium rather than a potentially unstable color center.
As an interesting side-note on this material, it tends to show the simple "imperial-style" termination you'd normally think of in true Brazilian imperial topaz rather than typical blocky or multifaceted terminations you'd see from most other locales.

If you'd like to read further, there is a good article on this material from Gems and Gemology in the '86: E. Gübelin et al., “Pink topaz from Pakistan,” Fall 1986 Gems & Gemology, pp. 140–151.

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 Post subject: Re: Pink topaz - is it treated?
PostPosted: Mon Jul 22, 2013 9:15 pm 
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Thanks! that G&G article was very interesting.. the pakistani material has a violet overtone that is missing from this stuff, and the R.I. is about .01 to .02 points higher.. I'll ask for an r.i. measurement.

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 Post subject: Re: Pink topaz - is it treated?
PostPosted: Thu Jul 25, 2013 6:41 pm 
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I had the guy have an r.i. test done from a stone in the lot.. didn't tell him anything.. Here's the result

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From the fall '86 article in G&G we see that the pink topaz has an r.i. above 1.63, so it looks like this is the good stuff.. the lower quality material that can be heat treated has a lower r.i. as shown..


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 Post subject: Re: Pink topaz - is it treated?
PostPosted: Thu Jul 25, 2013 11:32 pm 
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The material sure is pretty :D . I hope you'll be posting in the Off the Dop section soon!

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 Post subject: Re: Pink topaz - is it treated?
PostPosted: Fri Jul 26, 2013 1:40 am 
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Hello jleb ,

Assuming the stuff is still in namak mandi you can ask the vendor to have it checked by Mr Hamid Usman , a member of this forum and associated with a different lab than the one ran the test..there is another lab in Lahore , a one man show but a good reliable AIGS graduate is running it .

Just for your info , Katlang mine has produced hardly anything past several years , there is a new closeby site at shamozai producing lighter pink and being marketed under older and famous name. Would the RI parameters mentioned by you work for a different area might be worth checking.

Happy hunting.

Mazhar


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