how common is heated spinel?

[colormyworld]

Crasru, presume no such thing! The research I linked to is legitimate research. The other links are imo not legitimate research. Do a little digging over at mindat about the author.

While diffusion in corundum can be done I don't think spinel will stand up to the high temps needed to achieve the same results seen in corundum.

 

[digitaldevo]

ANY material can be diffused pretty much, it is just a matter of finding the proper combination to do it. Temps change with the material and the material being diffused.

Are they diffusing it currently? Probably trying to as I type this, but I do not think they have succeeded as of yet.

The only treatments I know and have seen personally for spinel are heat and clarity enhancement in the form of oiling as well as impregnation of some sort of resin/epoxy. With the later not being super common, but did test around a dozen samples from Ebay that were. Heating only improves certain colors IIRC. In most it does a whole lot of nothing. This is why it does not really affect the value one way or the other, heat treatment that is. But, yes, it needs to be disclosed if one knows or can tell. Not always that easy though.

Garnets being the same way, with rumor having it that there is a method to turn some of the chrome(or something, forget exactly off hand) bearing yellow grossular garnets into green grossulars, aka. tsavorites, but I have not found nor see proof of this either way as of yet. I also know they are clarity enhancing some garnets, mainly green and orange grossulars and possibly orange spessartites as well, but so far all samples I've seen and tested on these were either purchased from Thailand vendors via Ebay or directly or could be traced back to the same. So I don;t think it is super widespread, although the GIA did send out a warning back in the early part of 2000 or end of 1999 or close to there about coming across some fracture filled garnets, tourmaline, amethyst, and I forget the other material off hand, sorry. But I also came across some that at first glance looked to be fracture filled with resin/epoxy/CA but in the end turned out they actually were not. What did happen is apparently during cutting the faceter used CA to attach the stone to the dop, a common technique used now instead of or in combination with wax, and some of it managed to finds its way and seeped into a surface reaching fracture and just filled in the very top part of, not much penetration due to no heat to thin it and no pressure/vacuum to pull it deep down inside. So, just be extra careful before automatically jumping to a stone being filled when see some in a single fissure and only towards the surface, it most likely is just residual dopping CA. .

It is not too difficult to ID most of these treatments for anything though. Immersion + Microscope + Spectroscopy and SW and LW UV light(makes some filler glow wildly and others only slightly and some not at all) i is all that is typically needed and gives the telltale signs needed to know. But not every time nor every case, sadly. But those treaters are getting better every time!!

 

[chrono]

Crasru, presume no such thing! The research I linked to is legitimate research. The other links are imo not legitimate research. Do a little digging over at mindat about the author.

While diffusion in corundum can be done I don't think spinel will stand up to the high temps needed to achieve the same results seen in corundum.

CMW,
Since you’ve brought up your opinion that the other links are not legitimate research, please supply the reasons/proof why that is the case. I definitely like to know more about the author as well since you believe him to be of questionable reputation.

Crasru,
I thought about your thread last night and have come up with a couple musings:
1. How does the dealer/vendor know the spinel is heated?
2. When magnified, are there tell tale signs of heating?
3. My opinion is that a heated spinel (even if it doesn’t improve the colour) should be priced and worth less than a comparable untreated spinel for the simple fact that its internal crystal structure has been altered.

 

[T L]

ANY material can be diffused pretty much, it is just a matter of finding the proper combination to do it. Temps change with the material and the material being diffused.

Yes, they just have to find the right element/temperature combination, and that goes with any stone. Therefore, I personally do not think it can never be done. Treatment takes lots of time and research and is a big $$$ industry. If they can find a way, they'll do it. Never say never.

DigitalDevo,
Thank you again for your educated insight. I find your posts always informative and fascinating. You have taught me a lot.

 

[LD]

I don't think you have much to worry about with heated spinels. Pretty much everything I have read to date leads me to believe that heating while slightly improving clarity also causes the color to be less appealing to most consumers. Not much profit in that for gem vendors.

Crasru, would you please tell us more about these dye infused tourmalines being sold as "paraiba"?

OK it is easy if you Google "dyefused tourmalines" you'll find all the websites. I sent an e-mail to Ella just for my own knowledge (I am not sure which websites are considered forums and which are not) but there are at least 10 different places on the I-net where you can read about it or see the photographs. Of interest, I found no info about it at Palagems. They are usually good at mentioning new treatments. If I understand it right part of the discussion is around marketing terms. Given the new technology, only Brazilian Paraibas can be marketed as "paraibas"; the rest of the stones should be marketed as "paraiba-like" tourmalines. And the dyefusion has to be disclosed.

This is not correct. In 2006, the LMHC (Laboratory Manual Harmonization Committee) agreed that "paraiba" should refer to a species of tourmaline and not indicate a geographic origin. It can refer to gems found in Brazil, Nigeria, and Mozambique, and wherever new deposits of copper-bearing tourmaline may be found in the future. (Wording taken and adapted from the Gemselect website). There is a great amount of debate as to whether this decision was correct or not but to this day it stands. However, since "paraiba" denotes neon, glow and a specific chemical make-up, I doubt very much whether it would include diffused/dyefused tourmalines in this category.

 

[Arcadian]

This thread has been one heck of an eye opener. digitaldevo, thanks a lot for that info, its enlightening!

-A

 

[Lee Little]

Nice discussion. One point I do not see clarified is whether we are talking about surface or lattice diffusion. Both treatments are called diffusion but they are considerably different.
Surface diffusion was the first type and it is simply a coating that usually can be scratched off. Virtually any stone can be surface diffused and it is an easy ID for a gemologist.
Lattice diffusion refers to opening the molecular lattice and allowing a coloring element to enter the stone deeply. As far as I know, lattice diffusion has only been officially recognized as having been successful in Sapphire and only in using one element, beryllium. The lattice is opened enough for the beryllium molecules to enter by heating the Sapphire to a point where it is almost to melt.
The next possibility of diffusion into a stone on the market is Andesine but the treatment has never been accurately duplicated so we cannot be sure what that treatment really is that makes the strong red and green color. Some color was successfully diffused into some Andesine in a controlled lab but it was not pretty.
Currently diffusion deep into a stone is a very limited treatment and the reason Sapphire is the number one, and perhaps the only marketable candidate, is because it can take the punishment of extremely high heat. Spinel may be a very poor candidate for lattice diffusion.
I spent some time talking with Ted Themellis in his lab and was shocked at the number of treatments that are known, however, I believe there is also a lot of unnecessary nervousness about treatments that do not exist or are not practical. We need full disclosure and better education in this business to reduce the worry that takes the fun out of it. Best regards, Lee

 

[Arkteia]

I think that full disclosure is necessary. Again, I am thinking of Pala, a very reputable company, which states "no treatment", "heat treatment" and "unknown" in their descriptions. I consider it good practice. If vendors practice "don't ask, don't tell" policy it doesn't help anyone. If they you not know (which would likely be true in most cases these days), they should write "unknown" in merchants' certificates. Whether it should be reflected in prices is another issue, but unheated Paraiba costs more than heated, unheated ruby costs more than heated, so technically, any treatment should drive the price down unless it stabilizes a very soft stone (e.g. hayune).

 

[digitaldevo]

Glad I could be of help.

crasru, that is where it all boils down to! Proper and full disclosure of treatments. I do believe some treatments should be reflected in the prices, and an "Unknown" should not carry the same price tag as a known untreated stone. But that is really more so up to the consumer/buyer there, they are the ones who will kind of "set" the price for those with what they are or are not willing to pay for them.

To me, permanent treatments that do not weaken the gemstone, fade over time, or scratch off, are totally acceptable with proper disclosure. Like Be Diffusion, color goes all the way through the stone, so even if need to recut, stone is still safe, unless it was improperly treated from the start. I even understand and have no issue with clarity enhancements, except those that are more enhancements then they are gemstones material, lol.

They just need to all be disclosed, and price should reflect the treated state appropriately.