[Rockhounds] Halite losing fluorescence

[Axel Emmermann]

Kitty, 

One possible cause would be that the specimen has more than average
manganese content (which may aid the fluorescence, mangano-calcite is often
also pink).

As manganese is divalent is cannot simply replace sodium in halite. To
compensate for the charge deficit there would have to be a group of ions
that has an extra negative charge, like (NaCl2)-
If the specimen is a bit porous it's possible that the manganese oxidizes to
MnO2 which is gray.

One way to protect halite is to immerse it in a concentrated sodium chloride
solution for a few days. That would allow the KCl (which is the salt that
takes up the water from the air) to dissolve in the brine. The NaCl replaces
it thus making the specimen non-hygroscopic.

Be careful though with fluorescent specimens, you may extract the activator
or inhibit (especially with crystal defects as the activator)
fluorescence...

Cheers
Axel


Axel Emmermann
European Regional Vice President of the
Fluorescent Mineral Society
<http://www.uvminerals.org/>
=========================
Mineralogische Kring Antwerpen/Antwerp Mineralogical Society
<http://www.minerant.org/index.html>
Werkgroepleider/Workgroup leader: Fluorescerende mineralen/Fluorescent
minerals
Technische Realisaties/Engineering
My website:<http://users.pandora.be/axel.emmerman/home/>


> -----Oorspronkelijk bericht-----
> Van: rockhounds-bounces at lists.drizzle.com
[mailto:rockhounds-bounces at lists.drizzle.com]
> Namens Kitty & Bill Heacox
> Verzonden: zaterdag 13 december 2008 2:19
> Aan: Rockhounds at drizzle.com: A mailing list for rock and gem collectors
> Onderwerp: [Rockhounds] Halite losing fluorescence
> 
> Hi all, especially glowhounds,
> 
> I have several pieces of halite from Searles Lake in California and
> almost all of them fluoresce and phosphoresce white under SW UV.  One
> piece, however---which I got form John Betts four years ago---fluoresced
> a brilliant red-orange in a picture he posted to his site, and when I
> received it.  The specimen was a pinkish white under natural light, like
> most of my others.  I keep them all in an air-conditioned room because
> with our humidity here they would soon end up as a puddle of salty
> water.  Now I find that the one from Betts has changed to an ugly gray
> in daylight and does not fluoresce at all any more.  Anyone have an idea
> of what has happened?  I'm guessing that it has to do with microbes or
> algae in the water of the lake, but I don't understand why one piece
> would be so different from the others which came from the same lake.
> 
> Aloha, Kitty
> --
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