Post subject: Tenebrescent Zircon, let's talk.....
Posted: Sun Oct 04, 2009 5:32 pm
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Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
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:
Quote:
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:
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.
Joined: Tue Jun 03, 2008 4:40 pm Posts: 2667 Location: South Dakota
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 There is quite a difference between the colors in your pic..very nice!
_________________ MrAmethystguy ~ Some jokes just fluorite over my head!
Joined: Mon Oct 06, 2008 6:13 pm Posts: 5077 Location: Australia
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.
Joined: Sun Jun 24, 2007 5:40 am Posts: 424 Location: Southern California
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.
Joined: Sat Aug 18, 2007 11:46 pm Posts: 353 Location: Kingsport, TN
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...
Joined: Tue Jan 29, 2008 8:55 am Posts: 236 Location: Paris - France
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.
Joined: Thu Sep 25, 2008 10:33 am Posts: 840 Location: Mars PA
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.
Joined: Thu Sep 25, 2008 10:33 am Posts: 840 Location: Mars PA
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.
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