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 Post subject: Reversible Tenebrescence Revisited
PostPosted: Thu May 13, 2021 3:18 pm 
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Years ago, I wrote this page on hackmanite, and tenebrescence generally.
https://www.gemologyonline.com/hackmanite.html

There is a request on the page for additional information:
Image

After some years I got an email response from Todd Peters.
Todd wrote:
It sounds like the purple state is the low energy state where all the electrons have settled back down into their lowest energy orbitals. Almost like fluorescence, but with a very long decay rate. This makes me wonder if you could get those electrons up into yet a higher state with an intermittent (low heat/non destructive) UV laser and perhaps find a color past the whiteish.

Are you able to do any experiments with a UV/Vis spectrometer? If so, you may see some wild phenomena happening. So I did a quick search and first result: https://www.fluomin.org/uk/fiche.php?id=815 So much for my theories :)

The reverse hackmanite is interesting too. It sounds like heating drives the water out. Perhaps heated samples will return to normal when re-hydrated? Or, oxides are being formed and no hope for reversal. There is something in the back of my mind that is telling me that I am missing something about this... the connection to an industrial application; perhaps a photodiode sensor or something like Transitions lenses (https://www.transitions.com/en-us/). I wonder if the conductivity/resistance varies too, beyond just binary.--that would have some applications for sure. Or, if you really want to blow your mind check out "Surface Plasmon Polaritons" as it seems to be a good fit to this tenebrescence situation. The no-heating constraint is a tough one.


We have discussed the topic before. With hackmanite and also tenebrescent zircon.
Hackmanite: Purple color is achieved by leaving the stone in the dark for an extended period, or exposure to SWUV. Addition of heat kills the tenebrescent property for good
Image

viewtopic.php?f=20&t=24670
viewtopic.php?f=6&t=21907

Zircon: bright orange color occurs when left in the dark or heated over a flame
Image
viewtopic.php?t=9562
viewtopic.php?f=6&t=18048

In addition
Chameleon diamonds
Image
Photo by Robert Weldon from an article by Eloise Gaillou and George R Rossman
Color in Natural Diamonds: The Beauty of Defects
Which can be downloaded on Research Gate. (Contact me if you do not have a membership)

Scapolite:
Image

All insights welcome!


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 Post subject: Re: Reversible Tenebrescence Revisited
PostPosted: Thu May 13, 2021 5:46 pm 
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From what I understand irradiating the scapolite increases its tenebrescence a lot. I don't know if it's true though.

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 Post subject: Re: Reversible Tenebrescence Revisited
PostPosted: Thu May 13, 2021 9:25 pm 
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Stephen Challener wrote:
From what I understand irradiating the scapolite increases its tenebrescence a lot. I don't know if it's true though.

:smt017 Yes, that's one more thing to add to our lab.....a cyclotron.


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