Heavy Metal Diffusion Part II

[YourGemologist]

To receive the whole story from our Tucson Seminar please use these links: http://www.schoolofgemology.com/Diffusion1/SectionOne.pdf

http://www.schoolofgemology.com/Diffusion2/SectionTwo.html

17 January 2009

The Diffusion of Heavy Metals into Gemstones: Pink Tourmaline!
Part II of III that will lead up to the ISG at Tucson 2009 Seminar!

In Part II of our investigation we are going to try to answer a question that a lot of folks have been asking about pink tourmaline. Those who have been in the business for a while know that natural pink tourmaline is relatively rare with prices ranging over $300.00 per carat. So why are we suddenly seeing big beautiful and virtually flawless pink tourmalines on the market for as little as $20.00 per carat?

We believe we have the answer, and it comes as part of our investigation into the Heavy Metal Diffusion of Gemstones….Part II.

Traditionally pink tourmalines are naturally included, and rather expensive due to rarity. Of course with the advent of irradiation of pink tourmalines the availability of cleaner stones occurred since formerly unsalable stones were made available to the market by the use of this process. But by all industry reports, the natural and irradiated stones were priced within the same range and mostly indistinguishable, other than the clarity issue which only those of us in the industry for a number of years would recognize.

Now, however, we are confronted with something different. Large flawless pink tourmalines available at a fraction of the normal cost, and all represented as being totally natural and untreated in any way. Upon investigation we found some rather remarkable issues regarding these stones. And using both high tech and low tech study methods we have been able to identify why there are so many large flawless, and very cheap, pink tourmalines on the market.

First, the high tech.

LA-ICP-MS

As we discussed in a previous edition, LA-ICP-MS is a high tech test that uses a laser beam to move across a gemstone surface thereby turning the gem material into plasma or a gaseous liquid sort of state. The unit then does a spectroscopy evaluation of the laser ablated material and determines not only what elements are contained in the gemstone, but also how many parts per million of each is in the stone. Noted as PPM.

The equation for elbaite tourmaline is thishttp://webmineral.com/data/Elbaite.shtml)

Na(Li,Al)3Al6(BO3)3Si6O18(OH)4

And for pink tourmaline the trace element that causes the color is manganese. (Mn). Note the term trace element. This is because manganese is not normally a listed constituent of tourmaline, and is only as a trace element within the crystal. And please note that iron (Fe) is also not listed.

We had the pink crystal in the image above tested using LA-ICP-MS by the good folks at Evans Analytical Group in Syracuse , NY . And the results were quite astonishing. Rather than the normal chemical equation for this crystal we found ourselves with a huge PPM of both manganese and iron (Fe), something that should not be in a pink tourmaline. Here is a graph to show the PPM. Normally the manganese would be down at the titanium level based on other testing, with perhaps only a trace of iron. But in this stone we found Mn levels and Fe levels higher than some of the elements listed in the proper formula. Here is a graph to show the details:

The aluminum (Al) and silicon (Si) are listed in the LA-ICP-MS as matrix due to their being the matrix material of aluminum silicate of tourmaline, but by importing the Al and Si numbers from the SEM tests we were able to create this chart. We have the actual chart created by Evans Analytical Group (EAG) and will present it at our ISG at Tucson 2009 seminar on this subject, and in an upcoming book.

EAG also laser ablated the crusty stuff on the outer surface of this pink tourmaline crystal. A report on that will be provided at Tucson also, and in the previously listed book project we are developing.

Based on the above it was obvious that there was far more Mn and Fe in this gemstone than could possibly be natural. At this point we moved to the low tech investigation.

Low Tech Investigation

The first thing we noticed about many of the strange tourmalines was that some offered a significantly different Raman scan than what was normally reported by the RRUFF files and testing of our own ISG collection of tourmalines. This led to our theory that we might have found the first indication of synthetic tourmaline on the market, a theory that was later proven to be incorrect. However, the Raman scans were verifiable, repeatable, and eventually told part of the story. It seems that some of the specimens sold to us by Thai dealers as elbaite “Paraiba” pink tourmalines were in fact liddicoatite from Madagascar . A fact confirmed by the RRUFF Broad Scan with artifacts R060969 for that gemstone by Michael Scott of Antandro Komby mine, Manandona River , Antsirabe , Madagascar . This exactly matched over 50 of our scans. We found that part of the original confusion was that that another lab had listed a Raman scan R060635 that showed a stone from an “unknown” source, and without the Broad Scan with artifacts that was required. Once we found Mr. Scott’s Raman report from Madgascar we had the answer and were able to clarify that issue.

The next issue was the reddish brown and sometimes yellow crusty material that we found on the tourmaline crystals we obtained from Thai dealers. We did not find this on any of the specimens obtained directly from Nigeria , Pakistan , Brazil or other locations where we were working with local dealers. This crusty material on the crystals was only being found on tourmalines purchased from Thai dealers. And one thing was very evident from the beginning, this material was highly magnetic. Which begged the question: If the LA-ICP-MS showed an extraordinarily high content of iron in the Thai goods, and the crusty material on the Thai goods was highly magnetic, perhaps there was a connection.



Gem Identification by Magnet

At the AGTA Spectrum Awards dinner in 2008 we had the pleasure of the company of Sylvia Gumpesberger of the Gemmological Association of Canada who also happened to be a pioneer in the identification of gemstones using magnets. We have previously exhibited how this works here in this newsletter. But more important was Ms. Gumpesburger’s report published in the GIA Gems and Gemology Fall 2006 edition that listed pink tourmaline as presenting study specimens that were both responsive and nonresponsive to the magnet. This gave us the answer to our question.

Over the past few months we have carefully obtained pink tourmaline study specimens from a variety of sources. These included buying direct from the mine owners and operators in Nigeria , Brazil , Pakistan , and other sources. We want to stress that in every case the pink tourmalines from these sources, #1 were not magnetic, and #2 did not show any of the baked on crusty red and yellow material.

However, virtually all of the stones we obtained that were both magnetic and showed the same brown crusty material baked on…..came from dealers in and around Bangkok, Thailand. Let’s look at some.

For this demonstration we used Sylvia's concept of a method to test magentism in gemstones. And it worked well as a simple wire attached to a free swinging string, an industrial strength magnet, and a set of demarcation lines on the table to use as a meter. By allowing the specimen to free swing till completely still at the first line, then simply sliding the magnet to the point that the specimen touches it, we were able to formulate a test protocol to determine the magnitude of the magnetism of the stone.

Below left you see a natural Pink Tourmaline crystal imported to the ISG office direct from Nigeria. (we are going to post up all of the credits for everyone who helped with this next week). It shows no magnetic reaction. At right is a pink tourmaline crystal obtained from a Thai dealer that contains some of the reddish baked on clay material. It gave us a positive reaction to the magnet.














Below left is a liddicoatite tourmaline crystal we have had in the ISG office for several years. It gave us no reaction to the magnet. Below right you see one of the faceted liddicoatite pink tourmalines that we obtained from a Thai dealer and it gave a strong reaction to the magnet. Demonstrating that the high magnetic Fe content of the crystals we have do in fact permeate inside the finished stones as this faceted liddicoatite tourmaline showed a strong reaction to the magnet while the known natural liddicoatite did not.














And perhaps most telling are the images below. Below left you see a beautiful natural elbaite pink tourmaline that I purchased from Eugene Beck in the Amsterdam Sauer offices at the 580 Fifth Avenue building in New York over 10 years ago. At right is a pink elbaite tourmaline with some classic inclusions we have identified as being present in many of the treated stones, and being from Thailand purchased last month. The natural Brazilian tourmaline shows no magnetism, while the pink tourmaline from the Thai dealer shows strong magnetism.














As was proven to us by the work of Ted Themelis, you cannot diffuse heavy metals into gemstones without leaving some kind of identifiable footprint. Since the magnetism was one footprint, we decided to pull out our Dixie cup immersion cell and have a look inside.

We cut the pink tourmaline crystal you saw at the top of this page in sections. Part has been sent back to EAG for additional LA-ICP-MS on the stone. The other part you see at left and below.

Notice that the pink coloring is blotchy, and follows the needles that extend into the stone. This is how the diffusion is being done and we will talk about this more at Tucson and in our upcoming book. But I believe the photographs speak for themselves.

We have scores of specimens like this, with many more photographs that document this situation. We also have a panel of PhD’s who are reviewing the numbers from the LA-ICP-MS, SEMS, SIMS, XRF, XRD, Raman and other testing. We will be providing all of this information in our upcoming reports in various venues.
But the most important point that we need to stress is simply this: Other than the oddball screw ups where the diffusion did not take properly (that allowed us to identify this treatment) the results of heavy metal diffusion of pink tourmaline offers a beautiful result. It has the potential of adding a huge amount of viable gemstones to the industry that would otherwise not be available for sales. We must go forward with understanding and identifying this process for the good of the future of our industry.

However, we must have proper disclosure. So far we are finding that all of the treated stones are coming out of Thailand, and some from dealers who deal with Thai dealers, but the tracers all point back to Thailand. Just as the tracers of the andesine diffusion pointed back to Thailand and China . These treatments are identifiable, and they can be traced with enough time and patience…..and money. Money is the key and any assistance from anyone else in this industry will be appreciated. I do not hesitate with that. The consumers and grass roots members of the ISG community are carrying a huge financial load right now with none of the big gemstone industry organizations helping out at all. That must change. We need your support.

And finally, although more testing is being done we do have what appears to be a grass roots method to identify diffusion treated pink tourmaline through the immersion cell and magnetism. That is the end goal of this investigation for all diffusion treatments. These stones are viable, beautiful, and can be an important stream of revenue if we can just find ways for home town, independent retail jewelers to identify them in order to maintain consumer confidence in the product and the industry.

In the case of pink tourmaline we can. And we will post up more on the “how to” side of things in the coming weeks.

Part III coming next week.

Get the whole story here: http://www.schoolofgemology.com/Diffusion1/SectionOne.pdf

http://www.schoolofgemology.com/Diffusion2/SectionTwo.html

Robert James FGA, GG
President, International School of Gemology








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