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 Post subject: Tenebrescent Zircon, let's talk.....
PostPosted: Sun Oct 04, 2009 5:32 pm 
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I recently purchased a tenebrescent zircon. When it arrived in the mail, it was a moderate orange color which quickly faded to brown in about 20 minutes or so. I was told that if I wanted to speed up the conversion back to orange, I could heat it for about 20 seconds over a candle. I did, and WOW!!!! The zircon became hot orange, both figuratively and literally. Again, the color faded in about 20 minutes.

Just to refresh our definition of tenebrescence:
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Tenebrescence is an extremely rare optical characteristic, also known as reversible photochromism. It is the ability of minerals to change color when exposed to sunlight, after either being stored in a dark area for an extended period or subjected to UV radiation.The effect can be repeated indefinitely, but is destroyed by heating . Traditional tenebrescence is illustrated by this hackmanite sphere:
Image Image
Left: after 20 minutes in light; right: after 20 minutes under SWUV


Question:
Is the zircon exhibiting tenebrescence or another phenomenon?
It actually seems more similar to the effect moissanite exhibits when heated. When heated, moissanite turns bright yellow and it fades to almost colorless when it cools.
The only difference is that my zircon will get orange if I hide it in the dark for a couple weeks and the moissanite MUST have heat to change color.


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PostPosted: Sun Oct 04, 2009 5:56 pm 
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According to that definition it would not be teb. but something else..thats if heat destroys the ability..sweet stone..i have never seen one do that..and you said it turned A BRIGHT/HOT orange? that is pretty cool..i still think "Vampire" stone is good :D There is quite a difference between the colors in your pic..very nice!

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PostPosted: Sun Oct 04, 2009 8:25 pm 
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Another pretty one that changes with light is the Tugtupite. Most known from Greenland but also can come from Canada and Russia.
It also fluoresces while being tenebrescent.. The paler parts fade to white in the dark, stick it in the sun and it really starts to blush.

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PostPosted: Sun Oct 04, 2009 10:25 pm 
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You say it turns orange in the dark? Hmm. Sounds like it might be a tenebrescent stone, with orange as its "rest" color and brown as the "excited" color. It may respond to a visible wavelength instead of the traditional SWUV for hackmanite.

The definition quoted seems a little too narrow to me. If the stone changes color in the presence of any radiation, then slowly reverts to the original color in the absence of the stimulating radiation, then I'm pretty sure it fits the definition of tenebrescence. To require that the effect be generated only by a particular wavelength or band (SWUV) seems unnecessarily limited to me.

As for the effect being destroyed by heating, well, exactly how much heat did we say is involved? Most physical properties are destroyed or altered if you apply enough heat, so that is a safe criterion.

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PostPosted: Sun Oct 04, 2009 11:28 pm 
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It's my understanding that even slight heat will render hackmanite or tugtupite dead in the water....more specific than that I can't be.


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PostPosted: Mon Oct 05, 2009 12:51 am 
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Ever since John Dyer's post about his "weird zircon," I've wanted to get my hands on some of this stuff. Very cool! If anyone knows where one could procure some faceting rough that exhibits the phenomenon, please PM me...

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PostPosted: Mon Oct 05, 2009 2:49 am 
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Hello,

I also have two of these zircons in a jewel. When I take them out of my jewelbox, they are vivid orange and fade during the day to a "sandy beige". Back in the box again for one night, they will be orange again the next morning.

As far as I understood from my gemology classes, some zircons have a quite unstable cristal lattice and even slight heat and/or natural light are enough to disturb this lattice. If the change happens with light, the phenomenon is called photochromatism, if it is with heat thermochromatism.


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 Post subject: Zircon
PostPosted: Mon Oct 05, 2009 8:00 am 
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You can bought them here:
http://www.americanthai.com/html/zirc268.html


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PostPosted: Mon Oct 05, 2009 8:11 pm 
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Cool rock, Barbra. What is it about this zircon that causes the phenomenon? Which other mineral exhibits such rapid tenebrescence? Thanks!


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 Post subject: Strange zircon
PostPosted: Tue Oct 06, 2009 2:57 pm 
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Hilmar Bosch, a dealer in South Africa, sent some of a small lot of zircon that he had received. The color was rather nondescript as he put it. So he heated the zircon and it turned bright yellow, I believe. When he exposed them to light the reverted to the nondescript color faster than he had ever seen before. He sent them to me to see if anyone was interested in investigating them. I will look for them if anyone is interested in a piece.

Bruce


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PostPosted: Tue Oct 06, 2009 2:59 pm 
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By all means!


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PostPosted: Tue Oct 06, 2009 3:41 pm 
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Thanks Bruce. I would be interested in trying this material out. I'm such a nerd for this kind of stuff :D

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 Post subject: PM with addresses and I will look for the bag of Zircon
PostPosted: Tue Oct 06, 2009 5:21 pm 
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I hope you enjoy and take pictures of the color change in heating the zircon. I have not done it myself.

Bruce


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 Post subject: strange zircon
PostPosted: Wed Oct 14, 2009 5:56 pm 
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I found the lot of zircon I offered to give samples from in a dark draw and it was a pale orange when I looked at it. It changed to a nondescript gray brown (much like some color change garnet from Tanzania) after a short time in the light. It behaves exactly like the tenebrescent effect. I don't know if these samples have been heated or not.

Bruce


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PostPosted: Wed Oct 14, 2009 11:35 pm 
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How about "JECKEL-HYDEITESS' ? WINSTONE


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