The long and winding road of testing “Laurellite”

Laurellite is a name that  I have given to a new variety of  copper bearing Elbaite tourmaline from Mozambique, that demonstrates a Reverse Alexandrite Color Change from purple in natural light to blue to blue green in incandescent light.  I have covered the discovery of Laurellite and its possible extinction in the post,  I am not a heater, “Laurellite”, in which I promised years ago that I would reveal the long and winding road of testing the new variety of tourmaline.  I will try and fulfill that promise now.

Best Laurellite, color changer This gemstone demonstrates a reverse Alexandrite effect color change. It contains copper and comes from Mozambique. Oval Laurellite (5.37 carats) This gemstone is a Laurellite. It demonstrates a reverse Alexandrite color change. It contains copper and comes from Mozambique.

 

 

Now that I had two examples of a new color changer in tourmaline (pictured above) and had seen innocent and disinterested people easily see the color change, I had to have the gems tested and alert the world to the discovery.  But how could I submit the gems for testing in a credible fashion.   I have no standing in the Trade or ever even posted anything on the internet at the time.  You also have to be prepared to see color change in a gemstone.  This means taking the effort to observe the gemstone under different “white” lights and not just the average mixed lights that we live under in the modern office environment.  I had this abiding fear that if I sent the gemstones in cold, the laboratory would routinely and quickly declare them blue purple tourmaline, without any further testing and then list their weights and dimensions on the certificate.  Money please.

I did not feel that I was capable of penetrating the only gem laboratory that I had ever really read about, the Gem Institute of America (GIA).  But I did know a pair of gem rough dealers on the west coast that had had material donated to the GIA and some credibility in the Trade.  When I contacted my usual contact and promised to trade a small piece of “Laurellite” rough that I had preformed, for a piece of Afghan material, if he would attempt to get a GIA researcher interested in my proposed submission, he agreed!

Not only did he agree, but he succeeded in talking with a researcher in their library. The stage was set for sending one stone, my best, which is an emerald cut of about 5 carats, in for examination.  I heard later, informally of course, that when she received the gemstone and showed it to her superior, he thought it was a synthetic.  I still smile about that even today, because I knew then that I was right to send the tourmaline in and that I had them hooked.  A request came back from the GIA for more material and I submitted my remaining two pieces of “Laurellite”  the first oval I had cut and the preformed piece I had promised my co-conspirator.   I also supplied location information and some speculations about how the material was found.  Then I waited two years for the two articles about the submissions, to come out in GIA’s magazine Gems and Gemology.  The first one identified the new variety of Elbaite (tourmaline) threw preliminary testing and gave the background material I had supplied.  The second subsequent article was delayed by a misunderstanding, concerning the first attempt to get quantitative information on the gems.  The gemstones  were then supplied to another laboratory for the work to be done.  Finally after a third researcher had looked at the gems, the article was published.

I was disappointed that the final researcher had really not done any work on the gemstones after showing personal interests in the project at first.  He wanted rough that had a crystal shape that would make it easy to orient the rough with the c axis.  I work as hard as I could to get material like that, but it proved impossible to even any more “Laurellite” at that time.  His idea of testing the concentration of copper in the rough, at the same place that you observed the absorption of light down the c axis, still waits to be done.

The articles proved to be somewhat of a disappointment to me.  It certainly was exciting to hear on my birthday that copper, as a significant chromophore (color agent) had been discovered in gem quality Elbaite (tourmaline) from  Mozambique for the first time, but subsequent testing for their copper concentrations using LA-ICP-MS (Laser Ablation-Induction Coupled Plasma-Mass Spectrometry) showed the copper values in the article were only about third of their actual values.  In the conclusion of the second article the GIA states that the color changer, which they determined to be a strong  unique one, was probably a new variety and understanding its visual properties would be greatly enhanced by having an advanced  colorimetric analysis done.  But they weren’t going to support it.

Now while the trail was fresh I had to have an advance colorimetric study done on my wayward tourmaline.  I quickly contacted a researcher who had worked for the GIA and was an authority in the field to test my tourmaline.  He agreed to undertake the testing for a price and the emerald cut “Laurellite” was sent off again.  When it was received, the best thing that I heard was that “I am very pleased that you sent me this gemstone” (The complete text of one email.)  I still smile because I knew then that I was right in sending the gemstone and that I had him hooked (sounds like the GIA doesn’t it)

We decided to submit a paper on his research to the British Gemmological Society for publication.  He wrote a first draft, but since his native language is not English and Chinese is a very different animal, I ended up writing and rewriting the paper.  Much of the effort dealt with the researcher’s attempt to put forward his new theory about color changing.  My interest was that my “Laurellite”, not only had it’s Unique Reverse Alexandrite Color Change validated, but it was also the “smoking gun” that he had been looking for to shoot down the old theory and make way for his better theory of color change.  Finally, when I was about consumed, the article was publish.  I have since discussed this article with another researcher, that has some well founded reservations about the depth of the actual research done in article, but the observed color change in “Laurellite” certainly supports the new theory.

I will briefly attempt to explain the difference between the new and the older more accepted theory of color change, but I recommend that anyone with more interest read the article in the magazine that the British Gemmological Society publishes.  The commonly accept theory of color change in gems has the spectral distribution of light in the various light sources as the only cause of the effect.   The classic example, that I have heard over and over again is that of ruby, alexandrite and emerald.  All three of these gemstones are colored with chrome, which can express either a predominate green or red color depending on the rigidity of the electronic world within the gem material.  Alexandrite, chrysoberyl colored with chrome, has an intermediate level of rigidity between ruby (corundum colored with chrome) and its red and emerald (beryl colored chrome) and its green and therefore switches back and forth between red and green depending on the spectral distribution of the light.  Since “Laurellite” goes from a warmer/redder color (purple) in a cooler/bluer/natural light and goes to a cooler/bluer color (blue-green)in a warmer/redder/artificial light, incandescent, the traditional theory can not be the whole story.  The eye/mind combination that sees the world has evolved in a world where color consistency is very important.  (an orange on the tree would continue to be easier to find if it stayed orange as the day’s natural light varied).  This adaptation has lead to non-linear relationships color and tone level in some parts of the visible spectrum (orange/red and purple/blue).  A classic example of the effect of non-linear adaptation of the eye/mind is the printer problem.  It comes about when you try to make a line of blue/purple print darker by using more tint.  It doesn’t just get a darker tone level, it also changes color.  Now back to the gemstone.  The newly present theory, that is support by “Laurellite”, can be stated as it is the eye/minds adaptation to the world and the spectral differences in the light that cause gemstones to change color.  (Synthetic hypothetical light sources call luminants are actually used to define color change, theoretically.)

Where has the chase gone since the British Gemmological article?  Well the gems have gone to Japan where a the LA-ICP-MS work was done and I will post the results in a later post and then to Switzerland where more LA-ICP-MA work was done to augment their growing library of confidential information on Paraiba and paraiba type  tourmaline.  Unfortunately, I was not able to get any data from Switzerland.  They did say it was useful and thanked me after two years of waiting for the gemstones return.

Do I have ideas about why some copper/manganese bearing tourmaline change color others do not?  Why yes and I am glad you asked.  One thing that the LA-ICP-MS  analysis showed was that the “Laurellites” have significant levels of barium, lead and thorium that are high for tourmaline.   The GIA even questioned me about possible lead contamination due to polishing because lead had only been recently discovered in tourmaline.  Thorium is a radioactive element that has a very long half life and both lead and barium are the final end products of radioactive decay. (I am trying to have research done to determine what the original radioactive elements where before they decayed).  Now in my hypothesis, the original radioactive elements were alpha particle emitters like thorium.  An alpha particle is the nucleus of a helium atom and  produces massive damage to a substance impacted by it, but only penetrates a short distance into the substance.  If such a particle was released inside a tourmaline crystal (and it is presently happening because of the thorium) there should be indications of that damage and one of effects might contribute to the color change phenomenon.  I have had at least on researcher find my speculation substantive, but I failed again to get more research done.

There are crevices that I have not descended into with this story.  Damaged stones and peculiar behavior, but this post has the cogent points I wish to present on the  long and wind path of research in “Laurellite”.  If something new comes up I will post it.

Bruce

 

About Bruce Fry

I was born in Summit, NJ in 1947 and graduated from Summit High School in 1966. I graduated from the Colorado School of Mines in 1970 and after spending another year in graduate school, I left to see the world of Brazil. After spending some more time discovering myself, I ended up working for the Commonwealth of Pennsylvania for 32 years as an Air Quality Engineer in the Department of Environmental Protection. I retired in 2007 and took up faceting gemstones again after a long hiatus that reached back to my twenties. I had started cutting cabochons when I was 13 and bought my first faceting machine when I was 15, but ran out of money and time until I retired. My great love in gemology is tourmaline and the collection presented here represents my effort to get as much beauty and variety in the colors of tourmaline as I can. I was particularly lucky in being able to get unheated cuprian tourmaline before copper was discovered in gem grade tourmaline from Mozambique.
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