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 Post subject: Re: Secrets of the Gem Trade: Jewelry Television Special Edi
PostPosted: Tue May 26, 2015 12:25 am 
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Richard W. Wise wrote:
Scarodactyl, I spent sometime buying and selling topaz and visited the Brazilian mines outside Oro Preto. I don't believe that the topaz chapter is inaccurate, but I am always willing to learn and would appreciate your input. This is the time. Please be specific.

Hey! Sorry for how rude my earlier post is. I have been known to get worked up over topaz, especially when I'm short on sleep (which is most times since I started grad school). So please do pardon my earlier jackassery. I will have to read through the chapter again to write something more specific and meaningful. Unfortunately I keep my copy in my office. I may be going in tomorrow, though, so it's
As a quick note on Katlang: relative to Brazil quantities are certainly very low, but it's still a rather sizable deposit. I got a large parcel of pretty large and relatively clean crystals a few years back for about 16/gram, though that was a pretty rare deal. Given how nice the stones can be it probably deserves a bit of attention. And anyway, it's one of maybe three sites outside of Brazil which produce imperialish topaz, two if you don't count the mostly-uninspiring Zambian material. That said, I'd agree with your decision to not visit. The guy who sold me the parcel said there was some fighting going on in the mines and that the miners were "a little bit no good."

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 Post subject: Re: Secrets of the Gem Trade: Jewelry Television Special Edi
PostPosted: Tue May 26, 2015 8:12 am 
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Scarodactyl,

No offense taken. Given the tendency in the trade to protect sources, I try to be alert to information like yours. Also, I'm not always right!

I have rarely, in fact never seen a Katlang stone available for sale, which is the reason I kept to the Brazilian. If there is no market, what's the point? I do have a nice crystal specimen.

From your post I deduce that you are a cutter. I find independent cutters often have information that The Trade lacks. If you have a high quality image of one of your stones, even better.

Love to see an image. I can be reached privately: richard@rwwise.com.

RWW

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 Post subject: Re: Secrets of the Gem Trade: Jewelry Television Special Edi
PostPosted: Tue May 26, 2015 3:52 pm 
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I'm afraid I don't actually cut myself. I just love buying gem rough and having it cut.
The Katlang stones I got were actually deep red-orange when I first purchased them. This is apparently induced in champagney stones by gamma radiation, and it fades in sunlight. When heated, however, the stones turned a nice light pink-magenta (or 'cyclamen' as some have called the stones). And given their size and how clean they are, I'm very happy with how it turned out. I can see if we can get some good pictures.


Anyway, I got my hands on my copy again, so I will mention some specifics. Sorry for the two massive posts. I have thought about topaz a lot and I have trouble being concise.
"Small deposits of low-grade topaz have been found in ...mexico, Sri Lanka, Burma, Pakistan, and in Russia's Ural Mountains."
Well.... I think this has some issues.
To some extent, it depends what you mean when you say 'topaz'. On the one hand, you have the very unusual metamorphic topazes like those of Brazil, Katlang, Sanarka in Russia and Karengarenge, Zambia. This is the type of deposit that produces the most desirable stones, no doubt. They have that distinctive 'imperial' termination in the rough, and most importantly they have chromium. Chromium-bearing topaz is a completely different beast from common Cr-less topaz when it comes to color and color stability.
So if you're just talking about "imperial-type" Cr-bearing topaz, then you are right that the only meaningful sources today are Brazil and to a much lesser extent Katlang. The source in Sanarka is no longer worked and it's nigh impossible to find any for sale, and the stuff from Karengarenge I've seen has always been very pale and iron-stained. But if you're just talking about potential quality, the best of Katlang is easily equivalent to the best of Brazil. I imagine you've seen this picture before given how well-known the specimen is, but yeah:
Image
Similarly, the best of Sanarka topaz looks like the best of Brazil:
Image
So, you could certainly call those deposits small, but not necessarily 'low-grade.'

Inversely, there are plenty of deposits you can call 'low-grade' but certainly not small. Gem-grade Cr-lacking topaz is super common (in gem terms) and found many many places.
Large crystals and tumbles from pegmatitic pockets are very, very available. This complicates things a bit because Brazil, Pakistan and Russia produce both the common pegmatite ones and the rarer metamorphic ones. No doubt you've seen the giant piles of blocky Pakistani topaz crystals for sale, often a natural light pinkish-brown or irradiated to an unnatural deep brown. Similar big crystals have come from Russia, the Ukraine, Colorado, etc etc. They're huge deposits, and no doubt they would outweigh the production of Cr-bearing metamorphic topaz a hundred times over. Their production is usually not of great interest to the high-end gem trade for a few reasons, but nevertheless they could probably be addressed with a bit more precision.
From what I can tell, you generally have four color possibilities from this kind of deposit: colorless, blue, brown (of at least two kinds) and yellow. Really big colorless stones can cut amazing curiosities, but who cares. The browns range from pale golden brown to pinkish-brownto rich orange-apricot-brown (which is phenomenal--see the Tribute Pocket from Colorado) to gamma-irradiated deep red-brown (very common on eBay and elsewhere). They would be of real significance if they were photostable, but none of the pegmatite stones seem to be. The finest Colorado stones are a bit more fade-resistant and have strong collector value but it'd be a bad idea to put them in jewelry. That's an easy pitfall for people so it might be good to address.
There's pale to medium blue (pale blues are actually not very uncommon at all) but they don't really matter that much in cut stones now thanks to irradiation.
And finally, there are stable pure yellow stones (people think yellow topaz is common for some reason, but it's hard to find real rough). I only came across some of these recently, and they're awfully beautiful. For example, this stone in the GIA's collection from Sri Lanka:
Image

You also get blue/brown and blue/yellow bicolors, and maybe green from better mixing of blue/yellow or blue/brown.
And who can forgot the lovely and unusual Guerrero topaz from Mexico, with their often-stable red-brown coloration and strong pleochroism. They may have dwindled in availability, but they're still remarkable stones.

I think it's absolutely fair to focus on the finest stones from Brazil, but I think as it currently stands the chapter gives a wrong impression that topaz in general is all like Brazilian imperial-type. But really, when it comes down to it the Ouro Preto is a weird, weird deposit, and most topaz is very different.

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Last edited by Stephen Challener on Tue May 26, 2015 4:20 pm, edited 1 time in total.

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 Post subject: Re: Secrets of the Gem Trade: Jewelry Television Special Edi
PostPosted: Tue May 26, 2015 4:12 pm 
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My previous post was getting too long, so I thought I'd break it up into two--I hope that's OK.

Treatments:
You leave off one treatment which may or may not be important. If you take an imperial-type, Cr-bearing topaz of lesser color (pale pink, champagne, golden-yellow) and expose it to gamma rays, it turns deep red-orange. The transformation is incredible--the stones go from 'eh' to 'EH!!!' complete with glowing appeal in the color. This is commonly done to lesser stones from Katlang, but I tried it on some Brazilian stones and got the same result. The color is not stable--they fade back down pretty quickly in sunlight. The Brazilian stone I tested went right back to its original color. The Katlang stones held just a bit of orange, and apparently hold more. I read that this treatment became wide-spread in the 80s, to the point that many dealers were taping their topaz up to their shop windows to show that they would not fade in sunlight.
I assume the pink-producing process you mention is the "surface diffusion" (really just a coating, I guess) that we see so much of? Of course this does not turn the topaz itself pink, but I imagine that's just a product of how little concrete knowledge there was about that treatment at the time.

Color:
I have a bit of a nitpick on your description of pink topaz. Much of pink topaz isn't really 'pink' in the sense of 'lighter shade of red', it's often a more intense magenta or red-magenta. Magenta (or 'hot pink' as marketers have sold it) doesn't appear in the rainbow (since it's between violet and red) or in most gemological vocabularies, but it does matter. Take this fine Katlang stone, for instance:
Image
It's not really a light-toned anything, but it was sold as a pink topaz, just as almost all stones of this color would be. Really, it's red-magenta.
I've never seen much light purple offered, but then again it's hard for me to find purple of any kind at a reasonable price.
I said it before, but irradiated brown topaz belongs here. You've probably been on eBay and searched for imperial topaz, and seen quite a bit of it. It's prevalent.
It would probably also be good to mention the rare presence of blue in Imperial stones. I have one crystal with a green tip and one with a blue core. Very neat stones, and less well-known.

Overall:
Ouro Preto may produce the most and finest stones, but it's also the easiest to find information about. Other varieties and deposits are harder for a newbie to find reliable information on, and there's a lot of misinformation on the web. I know a book like this has limited space but it would probably be really helpful to people to give them a broader view of the world of topaz, even if the other sources are less important from a bulk production or high dollar standpoint. And from a historical standpoint (which is often muddled by the various myths about the name 'imperial topaz') it might be useful to mention the schneckenstein deposit in Germany, given its early importance in popularizing the variety.

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 Post subject: Re: Secrets of the Gem Trade: Jewelry Television Special Edi
PostPosted: Tue May 26, 2015 5:31 pm 
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Very interesting, thank you. You certainly know your topaz. I love your specimen, I have a similar one without the highly saturated color.

I try to stay with chromatic hues, both primary and secondary, in my descriptions. Terms like magenta beautiful but they are imprecise and therefore problematic. I am very well aware that a lot of light purple is called pink. Pink is a light toned red and purple is a modified spectral hue falling half way between red and blue. I have purchased both pink and red topaz though I have only seen one red, arguably dark pink, without a distinct secondary orange.

I agree that mentioning other sources might be in order.

Do you have any wisdom on the origin of "imperial."?

RWW

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 Post subject: Re: Secrets of the Gem Trade: Jewelry Television Special Edi
PostPosted: Tue May 26, 2015 7:30 pm 
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(And by the way, I do know that you probably already know pretty much all of that, but I have trouble stopping once I get started, and it's useful to preserve for later.).
I wish that were my specimen. Alas, I didn't have a spare 8k lying around for it.
Often times the Imperial name is attributed to the Sanarka stones being favored (or kept exclusively) by the Czars or something like that. Someone has gone through the literature and seemed to conclude that the Sanarka material wasn't found until 1800, long after the Brazilian stones were well known. I can't find the specific link, but I think Barbra has it on hand. Anyway, it seems rather convincing that the Russian origin is likely not much good despite its romantic appeal. Beyond that I do not know anything certain.

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 Post subject: Re: Secrets of the Gem Trade: Jewelry Television Special Edi
PostPosted: Fri May 29, 2015 8:07 pm 
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This is a 5x4cm. blue topaz crystal on auction now. This stone is from Klein Spitzkopje, Namibia. Once in a while Trinity Mineral will auction a Katlang crystal but not too often. WFSgems.com has a Pakistan pink cut stone but it does not look like Katlang material. Scott does have a ton of inexpensive precious topaz including one reddish orange he is calling imperial. He is more well known for a pretty good selection of Benitoite. His father was one of the former mine owners. Richard-You are correct with the Teofilo Otoni location. I often mix up the two Minas Gerais towns.

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 Post subject: Re: Secrets of the Gem Trade: Jewelry Television Special Edi
PostPosted: Fri May 29, 2015 9:21 pm 
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My two favorite colors of topaz are grape purple and strong magenta. As far as I know they have only been found in the Ural mountains and Brazil, but I would love to find out I am wrong. The book about Russian topaz is one I would love to have - but it is really pricy..


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