Laurellite a reverse color change tourmaline is unique.

I am sure that I have probably said too much about Laurellite on this site for some people, but questions have arisen and I wish to list the salient points about Laurellite that are important to appreciate it.

1,  Laurellite reverse color change phenomenon is not only unique in gemstones, both natural and man made, but to all substances known to man.  This is according to Yan Liu who did extensive work on the color change phenomenon for the GIA and work with my material for the last paper published on Laurellite.  (A colorimetric study of tourmaline from Mozambique which show a reverse alexandrite effect.  Published in the Journal of the British Gemmological Society 2006, 30, 3/4, 201-206).

2,  Laurellite is a cuprian Elbaite that contains both copper in the plus two oxidation state and manganese in the plus three oxidation state.  These are the only essential chromophores in Laurellite.  This combination of chromophores produces a blue/purple under mixed light and a blue to blue green under incandescent light which changes to violet in natural light.

3,  The unique change from  a warm color, violet, under a cool light source, (natural light) to a cool color, blue green, under a warm light source(incandescent) is why it is referred to as a reverse Alexandrite color change tourmaline.  Why some cuprian tourmaline display this phenomenon while other tourmaline with similar chemical properties do not, is unknown at this time.  (When I speak of a warm or cool light, it has to do with the relative amount of red/blue in the light, not the temperature of the light source.  Scientific work done in color analysis uses “luminants” which are hypothetical light sources that simplify the analysis, but can not exist in the real world.)

4,  Laurellite is not only rare, like all tourmaline that has copper as a significant chromophore, but it is getting rarer.  It is a very common practice to heat blue purple cuprian tourmaline, like Laurellite, from all sources of cuprian tourmaline, to reduce manganese in the plus three oxidation state to the plus two oxidation state.  This eliminates the red factor in the blue purple tourmaline and produces a cyan  color that is solely dependent on the concentration of the copper chromophore.  (This assumes that there is no other chromophore, such as iron, involved with the gemstone’s color).  The driving force for heating the material is the possibility of increasing its value many fold.

5,  Laurellite is a “smoking gun” when it comes to theories about why materials change color under different “white” lights, like natural and incandescent light.  Its reverse color change phenomenon can NOT be explained by the nearly universally accepted theory, that uses ruby, alexandrite and emerald as the ultimate example of why some color gemstones display the phenomenon of color change.  (All three are colored by chrome in the same oxidation state, but under different charge/structural environments in each gemstone)  Laurellite does have the minimum of two absorption peaks that a color change material needs to have, to be strongly effected by the changing distribution of waves lengths in different “white” lights.  But in addition to this factor, the non linear response of the human visual system, to the varying intensities of the different wavelengths, must be considered.  Without the adaptation of the eye as it evolved to maintain color consistence in our natural world the reverse color change of Laurellite can NOT be explained.

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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7 Responses to Laurellite a reverse color change tourmaline is unique.

  1. sheroleary1 says:

    Hi Bruce,
    I have read many articles and blogs you have posted, and I have learned so much from you. I am a fan of your hard work, and your beautiful cutting abilities.
    My name is Sher O’Leary, and I am an avid collector of cuprian elbaite from Africa. I have hundreds of GIA certified and non-certified “Paraiba” tourmalines. I am writing to you because I just received a GIA cert a few days ago on a 10 carat “Laurellite”, a cuprian elbaite that is a pure purple in daylight, and turns a green-blue in incandescent light. This is the first “reverse color change” Paraiba tourmaline I have ever had. It is really quite lovely in person. I wanted to share photos (and the GIA certificate) for this gemstone, with you. I have not been able to find your contact information, so I thought this would be the best way to chat with you. If you would like to see some photos and discuss this stone, you can reach me at 714-747-7437, or my email at; sheroleary@msn.com. I very much look forward to chatting with you. Sher

  2. Robsarge4 says:

    Hi Bruce. I just purchased 4.79 carat reverse color changing cuprian elbaite ring. I understand the stone was saved from heating because it was so beautiful. It’s amazing how it can be a medium sapphire blue under artificial lights with a hint of green. In natural light it becomes an iolite violet color. Could it be a laurelite? I am happy to send photos. I’d love to know if it can included in the laurelite family!

    • Bruce Fry says:

      Hi Rob,

      Sounds like you have a winner and a beautiful Laurellite. It is about the same size as the discovery stone that I sent to the GIA. There are no pictures on my certification, but GIA does attach pictures now.

      I will say again, what you already know. Your stone is very rare and is growing rarer every day, because it can be heated to the perferred cyan blue. It’s color change is unique to gemstones and deserves to be protected as a great addition to the world of tourmaline and gemstones in general.

      Thanks for the comment.

      Bruce

      • Robsarge4 says:

        Thanks Bruce, they have a Laurellite for sale on the gem shopping network. It turns green to violet. The stone is about 6 carats and its set in a ring and is GIA certified. It was just on last night. They are asking 32k for the ring!

  3. Bruce Fry says:

    Wow! I wonder if it is included and has been clarity enhanced. Inclusions would make the gemstone a much greater risk of breakage if it was heated to the preferred cyan blue. I have been talking to a dealer that buys paraiba type material and much of it has been treated with resins after being heated. The original emerald cut that I sent the GIA is almost flawless under 10 power and completely eye clean. This makes it prime material to heat if the dealer had known it contained copper. The other pieces of Laurellite that I have show more of an average amount of inclusions and veils for cuprian tourmaline from Moazambique. I have never used resins nor had any of my gemstones heated. Natural is what I strive for.

    Thanks a lot for the input.

    Bruce

  4. Robsarge4 says:

    Interesting thought. My stone has a few feathers under 10x loupe buts its pretty clean. I I hope the GIA cert would show any clarity enhancement they call it natural cuprian elbaite. Your passion for tourmaline is really wonderful. You should gather all the pictures you can of laurellites you know of. I can’t seem to photograph the violet in my stone. I clearly see it but my camera with or without flash sees blue.

  5. rexguo says:

    Hi Bruce, I’m new to collecting gems and came across your amazing website while researching colour change material. Do you sell any Laurellite or know where I can acquire a piece? I find it to be the most fascinating. If you’re willing to part with one, please email me at my username at gmail. Thanks!

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