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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 1:56 pm 
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Barbra Voltaire...

Nice article...Cr is very difficult to defuse and at much higher heat...Zoisite is cooked at a relatively low temperature thus not likely to respond...

The green element can be reduced but not always...I think the red element is also reduced so we see less brown...Brown may also be associated with yellow...

Now this raises a question regarding Bi-Color...As in Citrine Amethyst (Ametrine ) or Jadeite (Red) would concentrating heat on one end of a crystal produce a bi-color effect??


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 2:38 pm 
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The question of ametrine has been addressed before on the forum.
The short answer to your question is "no".
see:
viewtopic.php?f=24&t=12549


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 4:15 pm 
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Barbra Voltaire..

ThankYou but I prolley wasn't very clear on my question...

It was regarding the heating on Zoisite to produce a bi-color effect...I always get these crazy ideas every time something new is presented...I guess I will just have to buy a long brown Zoisite crystal and try it for myself???

Stand it vertical in water while heating the top end??...LoL!!


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 4:20 pm 
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Quote:
It was regarding the heating on Zoisite to produce a bi-color effect.
The short answer is "no" again.

The bi-color effect is caused by chemical differences. If you would like to read the entire G&G article on green tanzanite, let me know and I'll forward you a copy.
:D


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 4:27 pm 
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Barbra Voltaire..

I'm really not being very clear...Sorry...I'm not referring to the Bi-Color Green/Blue...I was just thinking out loud about a Bi-Color effect from Brown to Blue or some variation thereof...Prolley just more hot gas than anything else??


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 4:37 pm 
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Have you ever seen such a stone? I haven't.


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 4:48 pm 
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Barbra Voltaire...

NO but this is how we get to see new stones that have never been seen before...Strange and pointless ideas that some fool is willing to follow...

The story line here in Thai is that once upon a time a gem dealer in Chanthaburi had his jewelery in a steel safe when his home burned down...Upon opening his safe he found that his jewelery had melted but some of his gems were more beautiful than before and he didn't know why...From this the Thai Burner was born...

Like the Be treatment many times what we learn is by pure accident and a few times out of intentional experimentation...But even with the intentional we often discover something other than what we were looking for...


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 5:05 pm 
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Quote:
The story line here in Thai is that once upon a time a gem dealer in Chanthaburi had his jewelery in a steel safe when his home burned down...Upon opening his safe he found that his jewelery had melted but some of his gems were more beautiful than before and he didn't know why...From this the Thai Burner was born...

Well, enchanting story, but you realize that's not how heat treatment was discovered, right? :wink:


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 5:41 pm 
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There are instructions on heat treating rubies in Ahmad ibn Yusuf al Tifaschi's gemological treatise "Best Thoughts on the Best of Stones" which was written in 1253 (as translated in "Arab Roots of Gemology." It also contains instructions on creating a red gem simulant, though I'm not overeager to give it a try since two of the principal ingredients are realgar and orpiment(!)) It's been around for quite a while.

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 Post subject: Re: Bi-color tanzanite?
PostPosted: Tue Nov 06, 2012 6:03 pm 
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The earliest writings on gem treatments can be found in Pliny the Elder's Natural History, written circa 77-79 AD.

Ahmad al-Bīrūnī known as Alberonius in Latin and Al-Biruni in English, (a Persian-Chorasmian Muslim scholar and polymath of the 11th century.) wrote a document between 1040 - 1048 thoroughly describing the heat treatment of ruby in a furnace designed to melt gold.


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Wed Nov 07, 2012 4:46 am 
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Scarodactyl -n- Barbra Voltaire...

I admit to not being much of a history buff but just relating about how the Thai's say they became involved threw accident...I think in our recent times the Thai have been the most active in advancing heat technology for corundum even though they are relatively uneducated as far as chemistry/physics/material science and most other modern concepts...As far as I know they still put in some white powder additive blessed by the Monks that has been debated as to what it is...LoL!!

Cooking is all around me here...It's the local business with their winnings and failures alike...I admit to being rather intrigued by it and love to talk to the ones who I can converse with...My Thai is very very poor...They get results from total garbage that I still marvel at how they do it...Opaque ruby that hardly lets any light threw and a percentage will become glass filled facet grade...Remarkable transformations...

In talking to then I get new ideas thus the new high temperature fluxing technique and induction process...All of which still needs to be proven in practical application which I will share publicly with the locals in part but never in full...That's just the way it always is as there's some little something that's never shared at all...Kinda a little game as each one tries to discover what the other is doing...

Nice way to spend the end of my days rather than sitting on some porch with an old dog watching the children play (*..~)


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Thu Nov 08, 2012 4:32 am 
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I was curious so decided to look on the net..

Zoisite Rough...Basically I only see advertised Ruby Zoisite even when I do a search for untreated/unheated/brown Zoisite...

Then under Tanzanite Rough I get a rather mixed bag of gem material which usually claims that the blues are unheated....I really have to question this???

I know this is being a little too fussy but "Tanzinite" is specifically just the blueish variety usually heated and nothing else or am I mistaken??...But now I see Pink Tanzanite Rough/Trichroic Tanzanite Rough/Transparent Green Zoisite Rough that's bi-color blue/green and of course my Brown Tanzanite Rough all being advertised as "Unheated"...I'm just a little confused???

The "Trichroic Tanzanite" is especially funny!!!

I also see mixed parcels of reportedly unheated Tanzanite Rough with browns/blues/greens/pinks all mixed in...Excuse me but I really have to question all that!!

I realize that I have spent way too many seasons around corruption here in Asia and that it has tainted my mind but it's NOT only the locals....It's also to a very large degree the pilgrims who come here and engage in their market...I suppose corruption rubs off or they were trending that way before they became exposed...The point is that many many times a kilo/partial will be spiked to make it appear better than what it is...This is how they sell their junk by associating it with "Eye Candy" than charge a premium for a pick price...

So I suspect something along this line every time I see gems advertised this way...Heaters (Factories) will treat several kilos at a time and pick out their very best...Than they pick out their main market material and the rest is too small to fool with or of very low quality...The small ones can find their way into mixed parcels as a way to elevate it's value...In this case I fear heated Tanzanite is mixed with unheated and sold together as an unheated partial...The unheated material is prolley too small or not likely to produce the desired effect so sold as in rather than heated...

But I am the suspicious type so interpret this accordingly...


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Thu Nov 08, 2012 4:17 pm 
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Some of the most trusted, expert dealers in the trade stand by what they sale, including the stones you're suspicous of.

Amongst them are Multicolour, Swala Gemtraders, Africa Gems, & Pala Gems.

No, I don't question them at all.

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 Post subject: Re: Bi-color tanzanite?
PostPosted: Fri Nov 09, 2012 4:23 pm 
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ELVIS PRASIOLITE...

I'm not going to point any fingers at anyone in particular and don't recall visiting a web page of any or the companies you mentioned...

Just as a word of caution: Consider are there any reputable lab reports on bluish/purplish Tanzanite specifying NO signs of heat??

I would just suspect heat and suspect the labs would do the same??...Such as this:

Quote:
Tanzanite Verification Report

For the tanzanite verification reports, Gemworld International verifies that the gems are tanzanite, measure them for proportions, and weigh them individually. Although naturally colored tanzanite does exist, it is very rare and generally not detectible as to its natural origin. Therefore, it is assumed that all tanzanite sold has been heat treated to attain the blue or puplish blue color. The treatment is necessary to attain the color and is considered to be permanent. All tanzanites are examined by our staff of graduate gemologists.


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 Post subject: Re: Bi-color tanzanite?
PostPosted: Fri Nov 09, 2012 7:13 pm 
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Cut ThroatTraders wrote:
ELVIS PRASIOLITE...

I'm not going to point any fingers at anyone in particular and don't recall visiting a web page of any or the companies you mentioned...

Just as a word of caution: Consider are there any reputable lab reports on bluish/purplish Tanzanite specifying NO signs of heat??

I would just suspect heat and suspect the labs would do the same??...Such as this:

Quote:
Tanzanite Verification Report

For the tanzanite verification reports, Gemworld International verifies that the gems are tanzanite, measure them for proportions, and weigh them individually. Although naturally colored tanzanite does exist, it is very rare and generally not detectible as to its natural origin. Therefore, it is assumed that all tanzanite sold has been heat treated to attain the blue or puplish blue color. The treatment is necessary to attain the color and is considered to be permanent. All tanzanites are examined by our staff of graduate gemologists.


I think I mis-read your post. I was speaking of green, pink, yellow, Zoisite or Tanzanite, whatever you perfer.

Go to these websites. They are top teir, as reputable as they come. If one of them says they have an untreated blue/purple Tanzanite, I would expect it to be so, even without a report, which as far as I know, you can't tell the difference between a man heated or naturally heated Tanzanite. These dealers are either stationed in Africa, or travel there on a consistant basis. They go to the source, does not mean they can't be duped, but if anyone can be relatively sure about what, where & how they buy, these are the ones. :wink:

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