QuestionHello David,
I have been impressed with your down to earth attitude about gems and life in general that I have read, so I decided to email.
I faceted my first gemstone over 45 years ago and fell in love with the colors of tourmaline not long after. I am very involved with research on color in cuprian Elbaite from Mozambique and was able to purchase "unusual colors" of tourmaline that have proved to be cuprian before copper was discovered in gem tourmaline from Mozambique in a lot of reverse Alexandrite color changing cuprian Elbaite, that I cut and had analyzed by the GIA. Articles on the gems are in the G and G magazine under lab notes. I would greatly appreciate your slant on the following questions.
Is there any scientific support for the ability of copper in the y site in Elbaite to produce a green coloration in Paraiba/paraiba-like/cuprian Elbaite?
Have you ever had discussions about Dr. Rossman's original paper and its statement that Titanium/Manganese IVCT causes, along with copper the bright emerald like green in Paraiba.
The latest article in G and G about Mozambique and paraiba- like tourmaline states that iron is a significant chromophore in green cuprian Elbaite/paraiba-like tourmaline from Mozambique. Have you ever heard discussions about this fact?
I am trying to help write an article on paraiba/pariaba-like/cuprian Elbaite for the internet and I don't want to be too controversial, but I can't find any scientific support for the commonly held misconception that copper and manganese alone produces the green (along with other hues) cast in paraiba/paraiba-like gems. I don't want to propagate a lie by passing on a misconception.
I enjoyed the pictures of your purple tourmaline. I wonder if you had a spectrographic examination made of the gem to see if it had copper. I have found that it is the only valid way to discover if the color of the tourmaline is truely being influenced by its copper content. Quantitative testing for copper in tourmaline is still prone to error and just knowing that a tourmaline contains copper is insufficient to know if copper really influences the color. I think that this is a particulary difficult call with green to blue green paraiba/paraiba-like toumaline.
I appreicate your time and wish you the best in the world.
Bruce A. Fry
Answer
Purple tourmaline
Hi Bruce~
I'm sorry for the long delay in my reply. I did send a short reply initially to let you know that I wanted to look into some of these things before I replied but apparently the system did not take it. In the meantime I have been traveling a lot and away from the computer.
I am, like you, a big tourmaline fan. You have been cutting longer than I have been alive! I am afraid that the depth of my knowledge is not so much scientific as it is of value in the trade. I do have some opinions to share here but please understand that I am by no means an expert in tourmaline- I just seem to find myself constantly seeking answers!
The question of the ability of copper in the y site to produce green coloration in cuprian elbaite is a very good one and I find that the trade is caught up in nomenclature and not science which is really unfortunate. I would be very pleased to see more people like you asking questions about the nature of the color of cuprian tourmaline instead of bickering over whether to call it "paraiba" or not. I am afraid that to answer your question directly, no I am not aware of direct scientific evidence of this y-site correlation and cuprian color. I have never heard it discussed.
While we are talking about cuprian color it should be noted that it's not just hue- it is a property of the color that has not in modern literature been addressed to my satisfaction nor to the satisfaction of many in the trade and the hobby. We know that this paraiba/cuprian/Mozambican tourmaline is prettier, but we have industry groups to tell us what is pretty and what is not- and what is valuable and what is not- when they have no business doing so.
Is iron a significant chromophore in green cuprian elbaite or paraiba-like tourmaline from Mozambique? Well, not according to people that I know in the trade. This goes hand-in-hand with the titanium-manganese question. The cold hard fact is that we don't know the cause of these colors and we only speculate. I suppose that the more expensive my equipment and the more papers I have published the more my speculation is worth, but none of these researchers seem to be calling their findings speculation.
Bruce it would be wonderful if you could add some controversy to this field but do it with a scientific basis. Don't fall into the nomenclature issues or allow yourself to be bandied about by the trade- just talk about your test results and the conclusions that these allow us to infer. It would be very refreshing to read new ideas about this wonderful tourmaline because obviously the current body of knowledge does not tell the whole story. There is more work to be done.
You make a fabulous point about the quantity of copper and whether a given stone in impacted by the copper. It's not what the trade wants to hear, of course- they want a big price for a stone that has a report that claims copper. Mostly I try to sell beautiful stones and the price that purple stone fetched allowed me a small profit and I think it made someone very happy. I am not eager to pay for a tourmaline report these days when so much is unknown about the stone- even, apparently, whether the copper can be diffused into the crystal lattice! Can you imagine we are talking about this- when it looked like tourmaline, the untreatable stone, was already rife with controversy?
Bruce I just don't have any good answers for you but I am so grateful that you are asking these kinds of questions. When you do publish the paper online I would be honored to put a link on my blog to your work. It's an uphill battle getting solid information out to consumers but it can be done most certainly. There are more people now than ever who are not only interested in colored stones but are truly astute consumers who are dedicating a lot of time to being wise consumers.
Best of luck with your research!
David Fortier, GG
Tiptopgem.com
