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PostPosted: Mon Jul 27, 2009 7:25 am 
I thought man-irradiated stones were just exactly replicating what would have happened in nature anyway, had circumstaces been different. Thus surely it would be undetectable from a natural stone? Or does the fact that the process occuring in a shorter period of time leave tell-tale signs?

That said, thinking back to the FGA diamonds have that GR1 near-IR absorption line if irradiated, which I never quite understood.

However, I do agree with ROM though about natural blue topaz being more than merely a moot point. A naturally-coloured diamond rightly costs scores times more than an irradiated stone, and a Be-diffused sapphire rightly costs far less than a natural unheated stone. Surely the same principle of 'value through exclusivity' should be applicable to blue topaz as well - especially if it occurs at the low % that Bear suggests.

Blue will always be a popular colour, and topaz is a material with few weaknesses. I would have imagined that a rare natural-blue topaz would be quite a valuable commodity - assuming, of course, it's lack of human modification was provable.


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PostPosted: Mon Jul 27, 2009 9:14 am 
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ROM wrote:
Bear Williams- SGL wrote:
Just want to make sure terminology doesn't get in the way....when you say diffused, you are referring to the coating technology correct? We've been around the block a couple of times with the concept of diffusing of the transitional metal ions into the crystal lattice of topaz and tourmaline and we don't want to make the mistake in thinking that this is being done. :roll:

bw


Bear, I think you should look into the patented Pollak Heat Diffusion Process, developed by Richard Pollak, San Diego. His diffused topazes were originally sold by Leslie & Co., and the company was recently sold to Signity. Diffused topazes are now being sold by Stuller, for Heaven's sake!

From the descriptions I can find the process is similar to the original sapphire diffusion method developed in the 1970s or 80s which colored only a tiny surface region of the stones. It could be removed by chipping or recutting. It's not exactly a secret; there have been stories about it in all the major trade mags.

Link to Pollack Heat Diffusion Patent


Rick,

The link you sent discusses the process of irradiating these stones using gamma etc. energy sources. This I'm very familiar with. They are getting high energy atomic particles which have the energy (and are small enough) to enter just about anything including yards of solid rock.

And please know too, that we are familiar with the process of diffusing of iron and titanium into the sub-surfaces of corundum to create a more blue color or even induce asterism. This also is nothing new.

Have another look at what I was saying above.... "the concept of diffusing of the transitional metal ions into the crystal lattice of topaz and tourmaline..."

This is an entirely different matter, and while I don't disagree with what you are saying, please understand that I've already read the patents from Azotic and the others regarding the processes of their treatments, and I have also personally tested the stones that have been treated using these methods.

While they have very clever methods of marketing and language, and indeed very advanced ways of bonding the colorants onto topaz (or tourmaline, beryl etc.), it amounts to nothing more than a coating process, like electroplating.

If anyone has topaz or tourmaline that has been lattice diffused using any of the chromophore metals please send it along.

Bear


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PostPosted: Mon Jul 27, 2009 11:19 am 
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I think many of us hear the term "diffusion" and presume the principles are synonymous with the lattice diffusion of corundum. It is not.

Let's talk for a moment about the "thickness" of the diffusion seen with the Pollack process. It forms a layer on the surface of the gem approximately 200nm in thickness (G&G, Summer 2008, Coloring of Topaz by Coating and Diffusion Process, Gabasch, Klauser, Bertel & Rauch).
A nanometer is one one millionth of a millimeter.

The coatings used by Azotic are approximately 400nm in thickness and possess a sharp interface between the layer of colored coating and the gem material.

The Pollack process of coating the surface of the gem involves an interfusion of the coloring agents with the gemstone. But it is still a very, very thin surface layer.

It in no way is analogous to the lattice diffusion of corundum.


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PostPosted: Mon Jul 27, 2009 11:25 am 
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So Barbra, could we call this superficial diffusion as opposed to molecular diffusion?

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PostPosted: Mon Jul 27, 2009 11:28 am 
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Jason wrote:
So Barbra, could we call this superficial diffusion as opposed to molecular diffusion?

J-


hi Jason,
i would call it coating...

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PostPosted: Mon Jul 27, 2009 11:35 am 
Size-wise transition metal atoms/ions tend to be rather large - especially compaired to Beryllium, which has an atomic number of just 4 (and is thus the 4th smallest atom in the universe - after hydrogen, helium and lithium).

I always imagine it like trying to fly an airship through a dense forest. You won't get very far. A mosquito, however, will shoot though no problem.


Last edited by Kyriakin on Mon Jul 27, 2009 11:42 am, edited 1 time in total.

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PostPosted: Mon Jul 27, 2009 11:40 am 
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Good analogy!


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PostPosted: Mon Jul 27, 2009 11:56 am 
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...or maybe trying to shove cooked spaghetti through a steel plate?

:smt014


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PostPosted: Mon Jul 27, 2009 12:02 pm 
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"It is easier for a camel to pass through the eye of a needle than for large transition metal ions to pass though a topaz cyrstal.."


Hughes 19:24


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PostPosted: Mon Jul 27, 2009 2:31 pm 
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Kyriakin wrote:
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"It is easier for a camel to pass through the eye of a needle than for large transition metal ions to pass though a topaz cyrstal.."


Hughes 19:24


LOL THAT"S CLASSIC!

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PostPosted: Mon Jul 27, 2009 2:38 pm 
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Bear Williams- SGL wrote:
And please know too, that we are familiar with the process of diffusing of iron and titanium into the sub-surfaces of corundum to create a more blue color or even induce asterism. This also is nothing new.

Have another look at what I was saying above.... "the concept of diffusing of the transitional metal ions into the crystal lattice of topaz and tourmaline..."


Bear, have a look at what I said in my previous posts yourself. We’re tangled up in semantics. The word "diffusion" has a distinct meaning, as you’ve used it yourself above. You introduced the term "lattice diffusion" into the discussion. That's an entirely different matter and something I never claimed was happening. Using that definition did change the subject however!

I also never claimed the Pollack process was "new." In fact I compared it in broad general principle with surface diffusion of corundum dating from the 1970s. I did claim it was "diffusion" and that the method was patented.

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please understand that I've already read the patents from Azotic and the others regarding the processes of their treatments, and I have also personally tested the stones that have been treated using these methods.

While they have very clever methods of marketing and language, and indeed very advanced ways of bonding the colorants onto topaz (or tourmaline, beryl etc.), it amounts to nothing more than a coating process, like electroplating.


I’m familiar with the Azotic coating process also. A mod decided to delete the first patent link I posted, which clearly made the point about diffusion. The substitute link (not mine) is very general and incomplete. As for Pollack’s method, the authors of the Summer 2008 G & G article apparently agree with my use of the word “diffusion” in re: topaz. To quote briefly:

"In a sense, the new phase could be considered a coating on topaz. However, the coating phase is produced by strong diffusion and is probably followed by a chemical reaction establishing a new phase in the near-surface region. Furthermore, although the decay of the Co and Cr concentrations creates a region that may be considered an interface, this interface is much broader than that observed in a typical coating process, as can be seen with comparison with the pink coated topaz. Additionally, traces of the transition metals are still present in deeper regions (200 nm).

"Thus we classify the color treatment of the Ice Blue Topaz as a diffusion-induced process probably accompanied by phase transformation in the near-surface region."

I’ll split the semantic difference with you.

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If anyone has topaz or tourmaline that has been lattice diffused using any of the chromophore metals please send it along.

Bear


That would be interesting. But of course I never made that claim. Neither do I give much of a whoop what they do to topaz. I’m not likely ever to be spending 5 figures for a single piece of Imperial faceting rough nor do I deal in coated or surface-diffused topaz. I’m fascinated, however, by how much wealth has been created with the various methods of artificially inducing colors into and onto a plain, colorless, inexpensive “natural” mineral. Some great lessons about business and human nature can be learned from it.

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PostPosted: Mon Jul 27, 2009 5:11 pm 
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Rick,

Okay, I will split the difference in the semantics.

Perhaps the peer reviewers of G&G could have been a bit more stringent on the terms of definintion, esp. since the authors that generated the paper were from the very companies that are hawking the goods. (Signity & Swarovski)

Interesting though that they do state that first a precursor is set in the sputtering of these metals, in that a surface is created beforehand. I guess it needs something to stick to yes? One thing I found interesting in this G&G piece that I feel needs further explanation is where they say:

"This treated stone showed no evidence of appreciable diffusion apart from the defined interface, which is limited to depths between 350-400 nm." To me this sounds like they are arguing semantics between themselves. So what exactly is this defined interface?

They further state: "Within the limits of our experimental accuracy, we can state that no interdiffusion took place between the gold bearing SiO2 layer (present at a depth of 200nm) and that of the topaz." :smt119

Okay, nuff said on this topic for me. I'm off for a cold beverage and a ride on my scooter. Perhaps I might have a cicada bug diffuse into my teeth on the ride.

bw


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PostPosted: Tue Jul 28, 2009 10:17 am 
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Bear Williams- SGL wrote:
Perhaps the peer reviewers of G&G could have been a bit more stringent on the terms of definintion, esp. since the authors that generated the paper were from the very companies that are hawking the goods. (Signity & Swarovski)


Thanks for pointing that out -- I agree more attention should have been paid to the definition. In fact this whole matter of "diffusion" as it involves gems has created much confusion.

Someone with sufficient expertise -- you maybe? -- should write a piece explaining for us battle-weary troops precisely what is meant by the several permutations of the term: "diffusion," "bulk diffusion," "lattice diffusion," and any new variations that may have emerged while I wasn't looking :lol:


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So what exactly is this defined interface?


My question exactly. If "diffusion" isn't "diffusion," then what the bloody 'ell is it?

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Okay, nuff said on this topic for me. I'm off for a cold beverage and a ride on my scooter. Perhaps I might have a cicada bug diffuse into my teeth on the ride.

bw


Hope your cicada had a good flavor, at least. The cicadas we have out here in CA are some of the most seriously scary-looking insects I've ever seen. They remind me of nightmarish space aliens from a movie I saw years ago.

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 Post subject: Purchasing Imperial Topaz
PostPosted: Tue Jul 28, 2009 12:21 pm 
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I'm having an Imperial topaz ring made for my by a jeweler who I've dealt with on a number of occassions. They are a very old and respected company.

Right now they are ordering stones for me to choose from. I have asked for the peachy-salmon color stone in either an elongated baguette cut or pear shape. I have already chosen the setting.

What should I look for in gem quality and do you have any advice for me??

This is a great web site. I've appreciated reading all your comments and feel this would be useful for me. The ring is expected to cost around $1100.00 (which includes the 14 kt. setting). What carat size should I be able to get?


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PostPosted: Tue Jul 28, 2009 12:50 pm 
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Please keep in mind that this forum is NOT a consumer's venue.

You should be directing these questions to the person who is designing your ring.
Ask them to thoroughly explain the effects that color, cutting quality, shape and treatments may have on the price of the topaz.
Ask them to show you several gems in various price ranges and explain
why there is a price difference.
Ask them if there is an advantage to choosing an elongated baguette or a pear shape in the mounting you are considering.
Ask them if the ring is appropriate for every day wear or if there will be limitations on it.

I am sure they will be happy to help you make the best decision.


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