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 Post subject: Re: Purple tourmalines
PostPosted: Fri Aug 03, 2018 3:19 am 
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Location: Mars PA
Purple tourmaline is close to my heart and I have been fortunate to get to see and test the four non cuprian tourmaline discussed in this post. I also looked at a purple that had been determined to have copper by a qualified lab.

The four non cuprian tourmaline have very simlar absorption curves that do not show any signs of copper absorption. The absorption curves are dominated be what is probaby the manganese +3 peak while the much smaller iron peak in the red end of the spectrum impacts the stone's color relatively little, I think. The purples are definely reddish. The depth of the transmission window at the purple end does not appear to be exceptional and that left me wondering. Why are these tourmalines purple?

After I printed out the purples absorption curves I began to compare them with curves I have for my purples. None of my curves for cuprian purples fit the non cuprian purples curves closely. The absorption of copper +2 completly dominates the cuprian curves in most cases.

So on with non cuprian aborption curves. Now my collection of non curian purples is not rich, but the limited number of gems I have cut from probably Madagascar material did show similar curves with the the four non cuprian tourmaline. My best example of non cuprian purple is darker and smaller and not as red, but that is what I focused on.

Well I did say, probable manganese +3 curve, earlier because it finally became obvious that the probable manganese peak, which is usually around 530nm was at 550nm in the purples. This makes the transmission window wider in the purple end and is probably the reason the tourmaline are purple rather than red/pink. It would be very interesting to see if the non cuprian purples are liddicoatite rather than Elbaite. I don't think that it makes any difference whether is is Elbaite or Liddicoatite, but then I have no idea why the peak has shifted. And I have never read about the shift anywhere.

Anyone want to step up and try and get research one on an interesting tourmaline question? There are many, I am worn out from trying to get work done on the cuprian reverse Alexandrite color changer I have called Laurellite. My collection is always available for testing though the days of sending my beauties all over the world is over.

There is really little to say about the beautiful rich bluish purple cuprian tourmaline. Its tone was high and copper absorbes so much red that I do not have a strong enough light to really analyze it with my spectremeter. I did enjoy seeing it and I am sure that it is cuprian.

Bruce


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 Post subject: Re: Purple tourmalines
PostPosted: Sat Aug 04, 2018 11:58 am 
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Joined: Tue Jan 31, 2006 12:38 pm
Posts: 833
Location: N.J.
ruby302 wrote:
newark, we havent conversed in months-why ruin a good thing!! #-o Ur afraid of appraisers because U GOT NOTHING, EXCEPT BY MISTAKE!- :evil:
When you tell one of our well respected, knowledegable G.O. members to staple his mouth shut , I'm going to respond. Your obsession with these worthless, inflated appraisals is borderline insanity. Weren't you thrown off other forums for this very reason.This is only a disservice to any new members that think you know what you talking about. Your statement that I'm afraid of appraisers and have nothing-what does that even mean? Only with one of your well respected appraisers can one belt out a couple karaoke songs while his stones are being checked. Have you ever seen a non commercial quality stone? Here are a couple with rough and cutting by G.O. members. Don't try to silence the people that are knowledgeable.


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 Post subject: Re: Purple tourmalines
PostPosted: Sun Aug 05, 2018 2:37 am 
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bruce_tourm wrote:
...

Interesting. Thanks for all the info, Bruce!


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 Post subject: Re: Purple tourmalines
PostPosted: Tue Aug 07, 2018 12:18 pm 
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Very apt!


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