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Light Sensitive Mineral List

Posted by Peter Hargis  
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Peter Hargis November 06, 2008 02:30PM
I am searching for a Light Sensitive Mineral List. I've been able to find a handful of light sensitive minerals through research (Realgar, Topaz, etc.), but I'd like to get my hands on a list. If anyone can point me in the right direction, I would greatly appreciate it.

Thank you.
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Alfredo Petrov November 07, 2008 03:45AM
You can add a few more to your list: Vivianite, amethyst, proustite, pyrargyrite, xanthoconite, and all of the many species of silver halides and mercury halides....
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Steve Hardinger November 07, 2008 04:10AM
Kunzite and morganite
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Knut Eldjarn November 07, 2008 05:56AM
Not the least pink apatites (especially the ones from Pakistan/Afghanistan). An expensive specimen on display in the University museum in Oslo turned white after only a year with exposure to daylight ! Native silver and probably also most silver-bearing species to some extent. Making such a list in Mindat could be a good idea. It could be part of a section devoted to tips related to conservation of specimens ( there are also those that are heat-sensitive...). It would be valuable also beacuse the stability of specimens may differ from different localities. Thus the list should not only contain mineral names but a possibility to store data on observed storage stability under different conditions for minerals from different common localities.
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NH November 07, 2008 06:19AM
Native silver? What happens to it when exposed to light, increased tarnishing? Unlike silver compounds, there's nothing for it to decompose to...

I think there have been a number of threads on mindat about the light sensitivity of fluorite: see here, and here. Knut's idea about localities is a good one, as the stability of fluorite colors seems to vary a lot depending on the locality. There was another thread that covered fluorite and a few other minerals.
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John Sobolewski November 07, 2008 07:09AM
Pink Corderoite from the Cordero and McDermitt Mines turns a mouse grey color when exposed to light. John S.
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jacques jedwab November 07, 2008 08:54AM
This anecdote is one of those events which boggle your mind for years :

I was sitting at my refl. light micr., examining polished sections of Touissit ores (important details: high mag., oil immersion). Suddenly, I noticed several small worms growing out from the very polished surfaces. I didn't believe my eyes, and repeated the observations on other surfaces from the same ores. Same worms, but not on all mineral species. EMP-analyses of the worms showed native Ag, and various Ag-Sb species as the sensitive minerals. My opinion on my mental health was corrected when I found a paper by M. Stephens in Amer. Miner., 1931, 16, 532-549: "Effect of light on polished surfaces of silver minerals". Excellent paper in what concerns the older literature, a list of sensitive minerals, the theoretical explanation and experimental conditions. In his time, the light source was the carbon arc, which is of course much more powerfull than our lamps.

J.J.
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Ray Hill November 07, 2008 09:03AM
Light sensitive might also be applied to reactions/changes when exposed to light,

ie Sodalite, var: Hackmanite..
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Peter Haas November 07, 2008 09:28AM
Not to forget about fluorite.
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Knut Eldjarn November 07, 2008 11:13AM
Jacques,

thanks for answering the question from NH why silver-bearing minerals will react with oxygen, sulphur and moisture in the atmosphere (the sulphur may even be released from the specimen itself) especially when exposed to light. For a collector who grew up before the digital photography was invented, with a background in chemistry and having observed also how much faster silver objects tarnish when kept in daylight compared to in the dark in the household, your exprience when studying polished sections of silver minerals with a strong light source is very illustrating and does not come as a suprise.
It is therefore not only the question of light exposure (energy for chemical reactions), but also the availability of components that can react with the elements in the mineral. I.e. putting your wire silver specimen in a strongly lit and tightly closed glass case together with native sulphur specimens (which release sulphur fumes - you can even smell the crystals!)- is not a terribly good idea even for a short periode of displaying together native elements...
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Peter Hargis November 07, 2008 03:13PM
What a great response! Thanks for all the info. I think it's a great idea to start a section on Mindat.org that discusses light/heat sensitive minerals (including tips). I started a list of all the light sensitive minerals (inlcuding the ones you guys listed above)... take a look and add to it. Maybe after a while, we'll have a good list to post on here for other collectors, etc. I tried to list specific colors or locations, since this can have an effect on senistivity. It's just a start, not too much detail, but we can get a pretty detailed list going with all the knowledge floating around. Thanks again for the great response!

- Rockservation

*LIST HAS BEEN MOVED FURTHER DOWN TO MORE RECENT POSTS*



Edited 1 time(s). Last edit at 11/09/2008 04:57PM by Rockservation McGee.
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Steve Hardinger November 07, 2008 09:05PM
And then there are the minerals whose value changes with light: a specimen that appears fine under a dealer's lights at a show turns out to be not as nice as remembered when you get it home and examine it under your own lights.
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Ray Hill November 08, 2008 09:29AM
I just couldn't stop laughing and laughing Steve..how true...

and I believe that the colour that should be beside the Hackmanite, would be salmon pink and it should reside beside the varietal name...
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Knut Eldjarn November 08, 2008 11:38AM
Excellent point, Steve. Dealers know how to take advantage of the properties discussed here - not only simply by using bulbs that improve the colour in minerals. Many minerals fading in daylight may be "recharged" either by iradiation ( i.e. smoky topaz, smoky quarz, purple fluorites) or simply by using a UV-lamp ! The mineral Tugtupite (not on the list) is much more valuable in deep crimson-red colours - but this colour fades in daylight and can be enhanced with a UV-light lasting at least for weeks. Knowledgable dealers therefore "improve" the colour of their Tugtupites before offering this mineral at shows. It is especially problematic since the UV-lamp not only "restores" the colour of Tugtupite as found in nature but my personal experience is that it can deepen the colour way beyond what was the case when the rock was freshly broken.
Different varieties of Sodalite ( i.e Hackmannite) can be very susceptibel to colour changes due to small amounts of SO3-groups in the structure. I have myself experienced many times finding a large freshly broken and "bloody" surface of "Hackmannite"-Sodalite and when after digging I start packing the specimens, it is not possible anymore to locate the "Hackmannite"-specimens I put aside because they have turned grey or white like the feldspar and zeolites in the matrix. With the UV-lamp the colour can be restored for a brief period of time over and over again. This property of Hackmannite illustrates that it is not only a question of "light-sensitive" minerals but more specific sensitivity to specific wavelengths. With many minerals the colour changes (also fading) will be a function not only of the energy transmitted (intensity of the light) but to a very large degree on the dominant wavelengths that can resonance with the electrons (in the molecule or trace chromophore) and change their orbits in a way that alters the pattern of the wavelengths they later absorb or emit (and thus change what we observe as the colour).
From a practical piont of view, it is therefore interesting to note the susceptibility to fading (which I think is the key problem for mineral collectors) in relation to daylight and different kinds of lighting commonly used in mineral display cases. I know this makes the task more challenging, but I also know that this issue has been studied by many mineral curators ( i.e. at the Sorbonne) and that it is an important issue both for private collectors and museums who want to preserve mineral specimens for future generations to enjoy and study.



Edited 2 time(s). Last edit at 11/08/2008 12:26PM by Knut Eldjarn.
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Ray Hill November 08, 2008 10:26PM
Hi Knut
I agree with both you and Steve on this one. Fading, and darkening, conversely for me, are big issues regards a whole lot of minerals,Topaz and Vivianite being cases in point, in that I feel dealers need to be informed themselves and to inform their potential clients.

I had befriended a neighbour mineral dealer in Tucson that was from Pakistan, and asked him a number of times about the stability of the colour of his topaz specimens, and finally he showed me a much reduced price topaz that had already faded and admitted that most of the others would do the same and that was why he kept them away from the window during the show. In a way, I felt that this was false advertising if he didn't readily inform clients of this property of his specimens.

On the other hand,I have taken the opportunity to inform numerous dealers about the fact that their specimens of Vivianite would lose their gorgeous blue green colour if they kept them in the really high light part of their cases and they commented that they didn't care as long as it helped them sell the piece. Sadly at least two dealers I met subsequently had had to reduce the prices on their now almost black specimens of Vivianite which had been both large, well formed .
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Rock Currier November 09, 2008 12:41AM
One of the most common minerals that loose their color is the amethyst variety of quartz. It also had a very noticeable change in color depending on what kind of light it is displayed in. Amethyst commonly fades quite a bit over the years and appears to be somewhat in step with the degree it is exposed to sunlight. The first time I became aware of this was on my first trip to Uruguay years ago. Near one of the amethyst mines in the woods near one of the amethyst mines, I saw a pavement of amethyst crystals spread out on the ground under the trees. It was low grade material that they had no immediate market for and I asked why they stored it under the trees and they told me they did it to reduce the amount of fading in color. Later I carried out my own experiments and found that a nice colored Brazilian amethyst would fade remarkably in the sun in as little time as three months in the sun. All the dealers in amethyst in Brazil show their specimens away from direct light and try and sell them as much as possible in unlighted or under minimal lighting conditions in their warehouses. Ancient gem encrusted bible covers in Russian museums like the Diamond Fund or the Winter Palace have rather ugly gray looking stones in gold settings that were at one time beautifully colored Siberian amethysts. This and many more examples have been know for more than 100 years and for instance have been commented upon in Gratacap's Popular Guide to Minerals. I think color changes in mineral are much more extensive than most people realize because the changes can often be very gradual and often only noticed when comparing old specimens against similar ones that have been kept in dark storage for years. Vanadinite is a good example of this. I think even normal lighting in display cases can be the cause of minerals loosing or changing color.

Rock Currier
Crystals not pistols.
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Ray Ladbury November 09, 2008 01:50AM
You can add amazonite to the list--it bleaches white after exposure to light. Basically anything where the color is due to color centers will be light sensitive.
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Ray Hill November 09, 2008 10:37AM
All this just reinforces my decsion to not go to glass display cases for my collection, butr, rather, to keep it in Oak, dust protected cabinets. Oak works wonderfully at blocking light, I have found
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Peter Hargis November 09, 2008 04:57PM
More good info. I think it would be cool to include in the list what wavelength the mineral is especially susceptible to. This list still doesn't include that, but it has been updated to include some of the minerals listed in recent posts. If anyone would like to edit/update this list, feel free and post your updated version. I must admit that I am still an amateur collector, so much of this info is new to me and I'm hesistant to add much for fear of spreading incorrect info. A good idea might be to build out a table that includes mineral name, specific localities of concern, wavelengths, sensitivity to other variables (heat, moisture, etc.). I'm sure this has been done in other publications... Once again, thanks for the info.

LIST HAS BEEN MOVED EVEN FURTHER DOWN



Edited 1 time(s). Last edit at 11/10/2008 08:31PM by Rockservation McGee.
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Anonymous User November 09, 2008 06:10PM
The colouration varieties should be listed with their respective mineral species names; amethyst with quartz, kunzite with spodumene and morganite with beryl. Amazonite is a variety of microcline, the latter being a feldspar group mineral.

Philippe.



Edited 1 time(s). Last edit at 11/09/2008 06:13PM by Philippe M. Belley.
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Daniel Russell November 09, 2008 06:24PM
Cinnabar (see: http://www.minsocam.org/msa/collectors_corner/arc/cinnabar.htm)

Vanadinite

Djurleite (examples from Mount Gabriel. County Cork, Ireland, reported to be light sensitive in polished section, see
http://www.smenet.org/opaque-ore/PLATE52.htm

Aurivilliusite (see: http://minmag.geoscienceworld.org/cgi/content/full/68/2/241)

Willemite - (I have heard anecdotal claims that the apple green willemite from Franklin NJ will fade after long exposure to ultraviolet light... anyone have any direct observations?)

Parsons lists Pyrostilpnite, Tetrahedrite, and "Huantajayite" (a wonky variety of halite which ostensibly cotains silver halides, see http://www.mindat.org/min-30213.html )



Edited 3 time(s). Last edit at 11/09/2008 07:01PM by Daniel Russell.
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Daniel Russell November 09, 2008 06:46PM
Apparently, Kurt Nassau did a list of light sensitive species that was published in the following:

Howie, Frank M.
The Care and Conservation of Geological Material: Minerals, Rocks, Meteorite and Lunar Finds.
Oxford: Butterworth Heinemann, 1992.

I haven't seen it
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Peter Hargis November 10, 2008 08:31PM
*UPDATED LIST*

Apatite (pink - from Pakistan, Afghanistan)
Aurivilliusite
Barite (blue)
Beryl (maxixe emerald)
- Morganite
Bromargyrite
Calcite (from Elmwood, TN)
- Aragonite (w/ color)
Celestine (blue)
Cinnibar
Corderoite (pink - from the Cordero and McDermitt Mines)
Corundum (yellow)
Diamond (various colors)
Djurelite (from Mount Gabriel, County Cork, Ireland)
Feldspar
- Microcline
o Amazonite
Fluorapatite (pink)
Fluorite (numerous colors and localities)
Halite (blue, yellow)
- Huantajayite (contains silver halides)
Mercury Halides
Pararealgar
Pyrostilpnite
Pyrargyrite
Proustite
Quartz
- Amethyst (especially Brazilian amethyst)
- Rose Quartz
- Smokey Quartz
Realgar
Scapolite (violet)
Silver (native – can tarnish when exposed to light and moisture)
Silver Halides
Silver Halogenides
Sodalite (blue)
- Hackmanite (salmon/pink)
Spinel (red)
Spodumene (green)
- Kunzite
Tetrahedrite
Topaz (brown, sherry, blue)
Tourmaline (some pink, red)
Vanadinite
Vivianite (green, blue)
Xanthoconite
Zircon (brown)
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Anonymous User November 11, 2008 06:44AM
is Krohnkite light sensitive, i have it in a small glass box within a glass display case with a 40 watt bulb.
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Knut Eldjarn November 11, 2008 07:23AM
The green colour in copper-minerals is usually quite stable. I have seen many Kröhnkites in old museum displays and thye have a very strong colour even after having beeen displayed for a century or more.
Knut
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NH November 11, 2008 08:27AM
I'd watch to be sure you don't heat up the krohnkite too much with the bulb though - wouldn't want to dehydrate it (this could affect the color).
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Rock Currier November 11, 2008 11:52AM
It is rarely know how various wavelengths of light effect minerals. No one has ever done the work. I think in many cases, if you want to make a list of light sensitive minerals, that you are going to also have to list the species with a specific locality. A lot of work has been done on what causes particular colors in various minerals, but little on how various wavelengths effect those colors.

Rock Currier
Crystals not pistols.
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Alexander Ringel November 11, 2008 12:37PM
Hello,
i believe, that most colors are unstable, which cames from natural radioactive treatment.
Greets
Alexander
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NH November 11, 2008 06:17PM
Well, I wouldn't expect realgar to be affected much by 650nm light as compared to 400nm light: it just doesn't absorb much of it at all. I think the same is likely to apply to the other semiconductor minerals on the list (cinnabar, pyrargyrite, etc.): they will not absorb much light that has less energy than their bandgap (the bandgap for metallic-looking sulfide/arsenide/etc. minerals is in the IR, while that for clear minerals is in the UV, so for these, light absorption from the bandgap will be respectively unavoidable or unlikely except in direct sunlight). Presumably silver halides would be stable in light that had blue and UV wavelengths filtered out, as they should mostly be absorbing light below 410nm...you can use red light in black and white darkrooms.

For all minerals, light of a certain wavelength should not be able to have an effect on the mineral unless it is absorbed. For minerals that absorb in other ways than semiconductors do, it is harder to predict the absorption, but an absorption spectrum might be a good place to start to see what wavelengths might cause problems.
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Alfredo Petrov November 14, 2008 01:51PM
How did red spinel and pink tourmaline get on the list? Seem pretty stable to me.
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Daniel Russell November 14, 2008 04:51PM
NH:

Actually there was research done which indicated that the conversion of realgar into pararealgar was influenced to some degree by wavelength. See:

Douglass, D. L, Chichang Shing and Ge Wang
The light-induced alteration of realgar to pararealgar
American Mineralogist Volume 77, pages 1266-1274, 1992
Available online at
http://www.minsocam.org/MSA/collectors_corner/arc/realgar.htm

They concluded: " The alteration of realgar to pararealgar is dependent on the wavelength of the light to which the realgar is exposed, as determined from a number of experiments employing various types of filters. It appears that no alteration occurs at wavelengths shorter than about 500 nm." and that "peak transformation" to pararealgar (to coin an awkward phrase) occurred at wavelengths between about 500 and 670 nm, but no transformation occurred at wavelengths greater than about 670 nm. The reaction rate decreased at wavelengths above 560 nm and was very slow at wavelengths greater than 610 nm. "
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Daniel Russell November 14, 2008 04:55PM
A gemologist friend commented to me recently that cuprite was light sensitive. I have seen no documentation of this... anyone have any information?



Edited 1 time(s). Last edit at 11/14/2008 06:53PM by Daniel Russell.
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Knut Eldjarn November 14, 2008 05:04PM
There are many red or pink minerals which are probably unstable when exposed to strong light sources, but as Alfredo I would believe spinel and rubellites to be pretty stable. On the other hand, red/pink tugtupite (not listed) is subject to fading.
NH reflects on some of the practical consequences of these issues in relation to selecting light sources that reduce fading in minerals. I agree that the light waves that are absorbed will be the ones expected to cause the most harm. Many light sources also transmit a lot of energy in the non-visible part of the spectre ( IR and UV) which is usually of little benefit in displaying minerals but these wavelenhts will have a great potential for inducing fading. Thus for most practical purposes these guidelines could apply for the conservation of mineral specimens that are sensitive to light:
1. For as much time as possible keep the minerals in a closed box or drawer
2. Avoid exposure to direct sunlight and strong dayligth.
3. Avoid the combination of strong light, heat, moisture and reactive fumes like sulphur.
4. When displaying specimens, a dark room will permit exposing the minerals to less light and still have an effectful display.
5. The most safe light source would be an IR and UV-depleted source transmitted by fiberoptics (also to avoid exposure to heat).
6. An IR and UV-depleted light source with a colour-spectrum in the visible part of the spectrum balanced as in natural sunlight/daylight would have the potential of creating the most "natural" colours.
7. For especially unstable colours exposure to the same wavelengths corresponding to the colour of the object would (as suggested by NH) result in a very low absorbtion of light and thus less fading would be expected.

Many studies have been done on museum lighting and there are also companies specializing in systems that is said to give a considerable reduction in the fading of colours in different objects. Probably these experiences are relevant also for the preservation of unstable colours in minerals.
Knut
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Claus Hedegaard December 14, 2008 10:07AM
Knut,

> I have myself experienced many times finding a large
> freshly broken and "bloody" surface of
> "Hackmannite"-Sodalite and when after digging I
> start packing the specimens, it is not possible
> anymore to locate the "Hackmannite"-specimens I
> put aside because they have turned grey or white
> like the feldspar and zeolites in the matrix. With
> the UV-lamp the colour can be restored for a brief
> period of time over and over again.

This has happened to me too but I wonder whether the purple/pink colour of Sodalite var. Hackmannite is due to an extreme kind of triboluminescence? You add a lot of energy to the surface, when you crack the specimen, just as you do when exposing it to UV.

No clue how this hypothesis can be tested, but please educate me.

All the best

Claus

____________________________________________________________________________
Claus Hedegaard
Google me to find me!
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Knut Eldjarn December 14, 2008 12:28PM
Claus,

Interesting question and theory. I do not think you can induce the red colour in "hacmannite" just by inducing energy to the surface i.e. with the blow of a hammer without breaking the surface and exposing "fresh" sodalite. Because the mineral has a certain "parting", one could expect a more "mottled" colour if your theory was right since the amount of energy needed to break the bonds in the structure would be different along or across these zones of parting. But expect for these considerations it could turn out to be difficult to prove or disprove either theory.
Knut
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Anonymous User December 16, 2008 12:51AM
I see blue barite on the list. Do you mean blue fades to white/colorless? Because Hartsel barite turns from white/colorless to blue upon exposure to sunlight.
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Eddy Vervloet December 22, 2008 05:59PM
What about the pic of the day for 22 december?
Is that also the influence of light?

Greetings from France,

Eddy
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Rick Sinclair April 20, 2009 04:59PM
And last but not least in the under beryl add Aquamarine and don't forget the many varieties of opal and some agate (quartz var.) and rose quartz which can also fade, crack or change color.
various iron pyrites and copper minerals also can react if left in sunlight for a long time. It speeds up oxidation and breaakdown esp. in high humidity
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Peter Hargis April 20, 2009 06:12PM
UPDATED LIST - Pease note that this list is not all inclusive. Also, colors/localities listed are those particularly sensitive to light; however minerals of that same type but different color/locality may still be light sensitive. Minerals marked with a " * " are always light sensitive.

Apatite (pink - from Pakistan, Afghanistan)*
Aurivilliusite
Barite (blue)*
- “Hartsel” Barite can turn from white to blue in sunlight
Beryl (maxixe emerald)
- Aquamarine*
- Morganite
Bromargyrite
Calcite (from Elmwood, TN)*
- Aragonite (w/ color)
Celestine (blue)
Chlorargyrite*
Cinnibar
Corderoite (pink - from the Cordero and McDermitt Mines)
Corundum (yellow)
Diamond (various colors)
Djurelite (from Mount Gabriel, County Cork, Ireland)
Feldspar
- Microcline
- Amazonite*
Fluorapatite (pink)
Fluorite (numerous colors and localities)*
Halite (blue, yellow)
- Huantajayite (contains silver halides)
Marcasite (w/ high humidity - can speed up oxidation)
Mercury Halides
Pararealgar*
Pyrostilpnite
Pyrargyrite
Pyrite (w/ high humidity - can speed up oxidation)
Proustite*
Quartz
- Amethyst (especially Brazilian amethyst)*
- Rose Quartz*
- Smokey Quartz
- Various Agates
- Opal
Realgar*
Scapolite (violet)
Silver (native – can tarnish when exposed to light and moisture)
Silver Halides
Silver Halogenides
Sodalite (blue)*
- Hackmanite (salmon/pink)*
Spinel (red)
Spodumene (green)
- Kunzite
Tetrahedrite
Topaz (brown, sherry, blue)*
Tourmaline (some pink, red)
Vanadinite
Vivianite (green, blue)*
Xanthoconite
Zircon (brown)*

While this list will help you determine which minerals are light sensitive, I think it's important to re-list Knut's suggestions for all your minerals:
1. For as much time as possible keep the minerals in a closed box or drawer
2. Avoid exposure to direct sunlight and strong dayligth.
3. Avoid the combination of strong light, heat, moisture and reactive fumes like sulphur.
4. When displaying specimens, a dark room will permit exposing the minerals to less light and still have an effectful display.
5. The most safe light source would be an IR and UV-depleted source transmitted by fiberoptics (also to avoid exposure to heat).
6. An IR and UV-depleted light source with a colour-spectrum in the visible part of the spectrum balanced as in natural sunlight/daylight would have the potential of creating the most "natural" colours.
7. For especially unstable colours, exposure to the same wavelengths corresponding to the colour of the object would (as suggested by NH) result in a very low absorbtion of light and thus less fading would be expected.

Thanks to everyone who has helped contribute to this list... we're getting closer.

"Always do right. This will gratify some people, and astonish the rest." - Mark Twain



Edited 3 time(s). Last edit at 04/21/2009 03:34PM by Peter Hargis.
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Alfredo Petrov April 20, 2009 10:20PM
Peter, Your compilation will be very useful for collectors, but I think you need to distinguish (with some symbol, or italic type or something) between minerals that are always light-sensitive, like proustite and chlorargyrite, and those that are only occasionally light-sensitive, like rose quartz and sodalite.
Cheers,
Alfredo
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Amir C. Akhavan April 20, 2009 11:16PM
There's a fairly comprehensive list of light sensitive minerals and varieties in
a book that was long out of print and has recently been reissued.

R. Duthaler, S. Weiss
Mineralien reinigen und aufbewahren ("Cleaning and storing minerals")
Christian Wiese Verlag, 2008

I'm not sure if one should present there data here and what legal implications that has
(although to me facts of nature should be exchanged freely).

So what would be your recommendation?
I only got the 1999 edition

As a side note, of the two pink colored varieties of quartz, one pales always and quickly
and the other one apparently never does (but may develop cracks).

Amir
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Robert Rothenberg April 21, 2009 12:50AM
I had a number of Tuperssuatsiaite specimens from Aris that were a lovely mauve color when exposed in the vugs. They have all changed to green.

Bob.
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Peter Hargis April 21, 2009 03:36PM
Alfredo - I agree; I've added in notation for those that I know, but would you be able to edit the list for the ones you know that I may have missed? I'm still on the learning end of this and I do not want to pass on incorrect info.

"Always do right. This will gratify some people, and astonish the rest." - Mark Twain
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Adam Kelly April 23, 2009 08:29PM
This is wonderful. I brought a print out of this list to my local rockshop, and his eyes got big.
He had a wonderful elmwood calcite he had just put in the window.
I learned the hard way with a beautiful kunzite years ago.
Hopefully we can help to preserve some more minerals out there.
Thank again Peter and friends.

Adam K
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Peter Hargis April 23, 2009 08:51PM
That's great to hear, Adam! I'd hate to see an Elmwood Calcite fade (or any other mineral for that matter). It's unfortunate that some of the prettiest minerals are sensitive to being seen.

Amir - honestly, I'm not sure of the appropriate way to re-list some info from a published book. I'm with you, I think that facts of nature are public domain. It might depend on how we present the info, or we may just have to site the publication to prevent any issues. Do any of the site moderators know of the appropriate way to do this? It seems like we have a decent list going already, maybe we just fill in the holes using the list you have...

"Always do right. This will gratify some people, and astonish the rest." - Mark Twain
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Peter Lyckberg July 09, 2009 03:39PM
Most champagne colored topaz fade upon long sun exposure. Mexican and Utah crystals from low depth rhyolithic etc rocks and from pegmatites as in the followin.
One pocket in the Kazionnitsa Pegmatite, Alabashka Pegmatite field, Urals faded after some years in non direct sunlight. Other pockets in thei pegmatite produced blue topaz.
Blue topaz from a nearby pegmatite, the famous Mokrusha vein topaz occurs as light blue, almost colorless to deep blue crystals. Some of these have a light champagne color in the core and near the termination which fades upon light exposure and seem to become light blue with time. The blue color in topaz from this pegmatite also seem to be intensified by light exposure. Topaz from Shigar, Braldu and Haramosh areas of N Pakistan of light to dark champagne to almost orange color (not the irradiated orange-brown) fade with exposure for sure and from some pegmatites rather rapidly.
Ukraininan (Volodarsk/Volhynsk) is usually a very dark orange incredible color when found in the pocket. Even small shards are brightly colored and fade rather quickly in bright sunlight. The bicolored samples found in some pockets *light pinkish champagne and blue) seem to be more stable (at least for 15 years).
Blue kunzite from Kantiwa, Afghanistan turn pink after some days in direct sunlight.
Crocoite
Spodumene in general
Amethyst
Rose quartz! Crystals fade rather quickly unfder strong sunlight or strong display case lights.
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Alfredo Petrov July 10, 2009 12:58AM
New find of pink beryls from Afghanistan, turn deep yellow after only a few hours of sunlight! A friend of mine in Barcelona bought a lot of these and turned them all yellow deliberately because he didn't want his customers buying them as pink beryls and then complaining about colour change later.
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Adam Kelly July 10, 2009 01:12AM
Peter,
I got a topaz several years ago from a dealer in Denver.
He had gotten some beautiful pieces out of an old colection, but very few of the labels.
I worked for him labeling and pricing specimens, and he paid me with a few.
The topaz in question, has alternating phantoms of blue/peach.
In the core is a blue center with an obvious phantom of peach topaz piercing it.
I have never seen another piece like it, and would like to at least put a "possibility from" on the lable.
Unfortunatly, I do not have a digital camera anymore so no photos right now.
Did you see specimens like this from Mokrusha vein?
I was planning on bringing it, and a few other pieces to the Denver show again this year,
in hopes the some of my new mindat friends can help with some questions.
Hope you will be there.
AK
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Peter Lyckberg July 10, 2009 08:12PM
Dear Adam

I may come early to the Denver show i.e. the weekend before the main show. I amy also come to Springfield for the weekend and will be happy to have a look. The Mokrusha specimens are rather typical. Do you have the Murzinka issue of the Mineralogical Almanac. There are some good crystal drawings and photographs to compare overall morphology of crystals.

If you get a chance to make some photographs and send me I may be able to give you a good hint as to location.

I will just take this opportunity to also let you know that even some very old specimens in museums with original labels do have incorrect infortmation as to locality. Many western museum and even Russian have many old time russian specimens labeled incorrectly. In the 1980s I was supsicious to some but only after having visited these deposits myself and of course also gone through numerous museums collections (more than 100 museums and many private collections) of Russian pegmatite minerals, a pattern of misstakes was seen.

There are also some misstakes in nowdays localitues given for Pakistani and sometimes also Afghani specimens.
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Adam Kelly July 11, 2009 12:22AM
Peter,
I live about an hour up into the mountains from Denver.
Usually i'm at the show early, helping some friends set up.
The topaz I have had no labels at all.
I had guessed it might be from Brazil, Pakistan, or Afghanistan, but it was very different from everything I saw.
After seeing this thread, I looked at pictures from Mokrusha vein, and they are very similar to my piece.
Your descreption of colors from the local, perked up my ears even before I looked at pictures from there.
I also have a very green beryl from the same collection, that is very distinct, and unlike any others I have ever seen.
I am thankful to have access to such a knowledgeable, and experienced group of people here on mindat.
Now even more anticipation for the Denver show, only about two months now!
AK
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Anonymous User July 11, 2009 04:51PM
I talked to a friend at my mineral club meeting. He had found a beautiful lemon yellow phenakite on Mt Antero. He set it aside and continued digging. At the end of the day, he couldn't find it easily as it had turned colorless after one day in the sun. So that can be added to the list too.
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Peter Lyckberg July 11, 2009 11:11PM
Adam
I would love to have a look at the beryl too of course.
There are a several very good beryl localities in Russia as you know, some almost unknown.
I was in Colorado a few times also field collecting. I have a wedding to attend during the main Denver show therefore can not attend during that weekend. Maybe 1st weekend.

Phenacite indeed is very light sensitive. Orangish brown Phenacite form the emerald/alexandrite deposits in the Urals turn colorless or white depending on turbidity (inlcusions) withinn hours or days if exposed to UV light.

Peter
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Rob Woodside July 12, 2009 04:54PM
About a year ago I got a Sodalite from Jasun McAvoy and to my horror it darkens in UV!!!. Sodalite comes in two colours, the blue and a grey white. (Hackmanite is often quite white). I wonder if the blue started out like Jasun's piece and ambiant radiation darkened it to the typical translucent blue?
http://www.mindat.org/forum.php?file,11,file=6349,filename=sodalite3.jpg

There is some bizarre stuff in the literature about tenebrescence. One paper says that the pink colour of Hackmanite will return, if left in the dark!!!. Has anyone ever seen this? What is the difference between tenebrescence and long lived phosphorescence? This is a little like asking if the light is on when the refrigerator door is closed, but what colour is the Hackmanite before it is broken out??? There is very large energy densities at the leading edge of an advancing crack and so I wonder if the pink is excited by fracturing. This would mean that the hackmanite was actually white in situ and the pink is in fact a tribolumenescence??? I just tried to check this out with Bancroft and Hilaire Hackmanite. The Bancroft material Fluoresced orange like sodalite but never turned pink. The Hilaire material was slightly pink in tiny blotches, but not where I was scratching or breaking. I'll mark a pink blotch and then scratch it, once the pink has gone. Hackmanite is TRANSLUCENT white so it must be white in situ and the pink created on fracturing!!!
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Jolyon & Katya Ralph July 12, 2009 05:02PM
Easy way to test. Break a piece in the dark, leave it for 30 minutes, then pull it out of the dark and see what colour it is.

Jolyon
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David Von Bargen July 12, 2009 05:09PM
We've added fields to the database so you can indicate if there are problems in the display and storage of minerals. They are available for the mineral/locality list where only some locations present problems (displayed on the detail page as well as flowing up to the mineral page - after the cache clears) and also on the mineral page where all specimens would need special handling (light sensitivity of silver halides).

We should also include other things like humidity/deliquescent, dehydration, air exposure/oxidation, heat sensitivity.

The field is available on the detail edit page (you can get there from the i icon on the mineral lists).
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Rob Woodside July 12, 2009 05:13PM
Ahhh!!! Thank you Jolyon. Tenebrescence is supposed to be a light activated decay of colour. No light, no decay, so it should still be pink after thirty minutes in the dark. Sadly my blotchy pink material is not what I found years ago at St Hilaire. That material was a uniform pink on fracturing and that's what's need for this. Does any one have such material? and would they check it out? Thanks.
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Jim Bean July 13, 2009 03:37AM
Excellent addition, David!
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Peter Hargis July 13, 2009 03:13PM
Awesome, thanks for the addition!

"Always do right. This will gratify some people, and astonish the rest." - Mark Twain
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Matt Zukowski July 27, 2009 05:31AM
I decided to pick up the ball and add to the list started earlier. I went through mindat and FMF and the following is what i compiled.


List of Light Sensitive Minerals and Varieties
Information on sensitivity from particular localities listed under each mineral. Minerals marked with a " * " are always light sensitive.

Apatite
- (pink - from Pakistan, Afghanistan)*
- Pink apatites from Moro Vehlo Mine, Nova Lima, Minas Gerais.
- Himalaya Mine, CA
Aragonite (w/ color)
Argentite
Aurivilliusite
Barite (blue)*
- “Hartsel” Barite can turn from white to blue in sunlight.
Beryl (maxixe emerald)
- Aquamarine*
- Morganite
- Pink beryls from one find in Afghanistan turned deep yellow after only a few hours of sunlight.
Bromargyrite
Calcite
- from Elmwood, TN*
- from Santa Eulalia (yellow ones from Santa Eulalia temporarily turn pinkish on 15-20 minutes exposure to sunlight, turn white permanently with 30-60 minutes exposure to sunlight.
Celestine (blue)
Chlorargyrite*
Cinnibar
- Cinnabar will darken with exposure to sunlight.
Corderoite
- Pink Corderoite from the Cordero and McDermitt Mines turns a mouse grey color when exposed to light.
Corundum (yellow)
Crocoite
Creedite (purple creedites are VERY light sensitive)
Diamond (various colors)
Djurelite (from Mount Gabriel, County Cork, Ireland)
Feldspar
- Microcline
- Amazonite*
Fluorapatite (pink)
Fluorite (numerous colors and localities)*
- Sky blue fluorite from Haute-Loire, France turns colorless with 30 min direct sunlight exposure.
- Blue fluorites from Bingham, NM will fade with exposure to sunlight.
- Pale green fluorite from the Cowshill, Weardale area changed to purple almost immediately on exposure to daylight (not even direct sunlight!).
- Green fluorite from Weardale (Rogerley, Heights, Cement Quarry, and the old White's Level) are all potentially unstable, though to varying degrees. Purple color appears more stable. Deep green fluorite from the Rogerly (Solstice Pocket) permanently changed almost instantly to a muddy gray-green if exposed to a LWUV lamp; this process took longer in sunlight. Pale green fluorite from the Cowshill area changed to purple almost immediately on exposure to daylight.
- Hilton yellow fluorite is reported to be stable.
- Elmwood fluorite is reported to be stable.
Halite (blue, yellow)
- Huantajayite (argentian halite, contains silver halides)
- Pink halite from Searles lake is colored by halophylic bacteria and algae that fade with exposure to sunlight.
Inesite
Marcasite (w/ high humidity - can speed up oxidation)
Mercury Halides
- Aurivilliusite
Miargyrite
Morganite
- Morganites from various S. CA pegmatites would be left in the sun to "bring the pink up."
Orpiment
Pararealgar*
Phenakite
- Lemon yellow phenakite from Mt Antero turned colorless after one day in sunshine.
- Orange/brown phenakite form the emerald/alexandrite deposits in the Urals turn colorless or white depending on inclusion content within hours or days if exposed to UV light.
Proustite*
Pyrargyrite
Pyrite (w/ high humidity, light can speed up oxidation)
Pyrostilpnite
Quartz (most colored quartz are light sensitive)
- Amethyst (especially Brazilian amethyst)*
- Citrine
- Morion
- Rose Quartz*
- Smokey Quartz
- Various Agates
- Opal
Realgar*
- Realgar is only sensitive to green light; filter out the green light and its decay will be much less rapid.
Scapolite (violet)
Silver (native – can tarnish when exposed to light and moisture)
Silver Halides/Halogenides
Silver Sulfides/Sulfosalts
Sodalite (blue)*
- Hackmanite (salmon/pink)*
Spinel (red)
Spodumene
- Hiddenite
- Kunzite
Stephanite
Tetrahedrite
Topaz (brown, sherry, blue)*
- Most Thomas Range, UT sherry topaz xtals turn clear with exposure to sunlight.
- Some topaz xtals from east side of the Thomas Range, UT start out as sherry but turn pink after one to three weeks in the sun. This is due to an unusually high content of pseudobrokite inclusions. The pink is stable, at least after one year of leaving these in the sun.
- Some topaz from the Little Three Mine were collected as clear but turned blue upon exposure to the sun. Blue crystals that came out of the 1976 and 1991 pockets became much more blue with exposure. This blue color appears stable.
- Sherry colored topaz from Villa Garcia, Zacatecas, Mexico is reported to have stable color.
- The sherry colored portions of topaz xtals from Mokrusha Mine, Urals fade and seem to turn light blue with exposure to sunlight.
- Volodarsk/Volhynsk, Ukraine topazes usually start our dark orange but fade quickly with exposure to sunlight. Bicolored samples found in some pockets (light pinkish champagne and blue) seem to be more stable (at least for 15 years).
Tourmaline (some pink, red)
Tuperssuatsiaite
- Tuperssuatsiaite specimens from Aris started out mauve but turned green.
Vanadinite
Vivianite (green, blue)*
Wulfenite
- Red Cloud wulfenites will fade over time
Xanthoconite
Zircon (brown)*

Tenebrescent Minerals
Sodalite
- Hackmanite
Tugtupite

Why minerals are light sensitive
From a theoretical point of view light has a potential of deteriorating or fading minerals by different mechanisms and sensitive minerals might be grouped accordingly i.e.:

1. Light inducing photochemical reactions as is the case with silver-bearing minerals turning black on exposure to light when in an atmosphere with oxygen and sulfur, the changing of realgar to orpiment etc.

2. Light healing color centers in minerals. Color centers are structural defects in minerals that occur during growth or afterward (in the case of exposure to ionizing radiation). Minerals typically colored by color centers include amethystine and smoky quartz, fluorite, diamond, topaz, and halite. "Smoky" and "sherry" colored minerals typically get their color from exposure to ionizing radiation. Healing of sherry and smoky colored topazes is faster than smoky quartz.

Note that much of the color in minerals comes from the presence of chromophores (elements in structural positions in xtals that make their electron orbitals susceptible to absorbing or emitting light). Coloration caused by chromophores should be more stable. In some cases these changes may be reversible i.e. as for the Hackmannite variety of Sodalite containing a sulfite ( SO3-group) believed to be responsible for the color change.

Light sensitivity due to photochemical reactions and healing of color centers should be independent of locality, while chromophores from different localities may have widely differing light sensitivites.

Much useful information on the causes of coloration in minerals can be found at http://minerals.caltech.edu/COLOR_Causes/, and any mineralogy textbook.


Knut's suggestions for avoiding harmful effects of light:
1. For as much time as possible keep the minerals in a closed box or drawer.
2. Avoid exposure to direct sunlight and strong daylight.
3. Avoid the combination of strong light, heat, moisture and reactive fumes like sulfur.
4. Keep your display room dark when not in use.
5. The most safe light source would be an IR and UV-depleted source transmitted by fiberoptics (also to avoid exposure to heat).
6. An IR and UV-depleted light source with a color-spectrum in the visible part of the spectrum balanced as in natural sunlight/daylight would have the potential of creating the most "natural" colors.
7. For especially unstable colors, exposure to the same wavelengths corresponding to the color of the object would result in a very low absorption of light and thus less fading would be expected.
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Jolyon & Katya Ralph July 27, 2009 08:43AM
Add to the list:

Cuprite*
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Rock Currier July 27, 2009 12:09PM
Mat,
Light sensitive minerals is a huge undertaking. You get interested in something and no one else seems to be doing very much about it so you decide to start doing something about it. You have started. It will be interesting to see how far you will take it and how long you will stick with it and what it may become. You will find a lot of people willing to help along the way. Pretty soon you will start thinking about spectrophotometers and spectrum analyzers and start thinking about tests you can run to check out this or that. Keep going. It sounds like you have the beginning of a good article that you can publish here on mindat or in some magazine.

Rock Currier
Crystals not pistols.
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Peter Hargis July 27, 2009 06:48PM
Mat,
Thanks for the added info...it's a much more useful list now. I agree with Rock's comments... Being somewhat new to mineral collecting, I started this a while back to get a handle on which ones I can display without fear of fading. It quickly became quite the undertaking. I've tried to keep up with it, but with work travel I've dropped the ball. I appreciate your (and everyone else's) help with this.

"Always do right. This will gratify some people, and astonish the rest." - Mark Twain
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Keith Corrie August 05, 2009 05:03PM
As UV light is the culprit with many species losing their original colour, polycarbonate may be a useful way screening out most of these harmful photons. It is opaque to all wavelengths below 385 nm and therefore should prevent degradation while still permitting up to 87% light transmission. There are a number of polycarbonate products available with some manufacturers claiming 98% protection.

Blue barite collected from Peak Hill Sidmouth Devon UK in my display cabinet has lost an estimated 50% colour over a 6 month period. By constructing a polycarbonate covered section in my display case I hope to at least slow up some of the attack.

Keith



Edited 1 time(s). Last edit at 04/30/2012 01:57PM by Keith Corrie.
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Matt Zukowski August 16, 2009 11:33PM
I got a great book from Amazon: Howie (1992) The Care and Conservation of Geological Material.

This book pulls together a ton of the physics and chemistry of mineral specimen degradation. It is well written. I believe that whatever I was imagining pulling together about this subject has been done before, at least as of the 1992
copyright of this book.

One of the interesting suggestions he has is that a good test for color stability is to heat a small fragment to 200C for an hour or so and look for changes. No change indicates long-term color stability to light. This test should not be used for yellow sapphire.

Please note that Howie, 1992 also includes information on thermal and humidity sensitivity, and includes chapters on the special sensitivity of elements, of sulfides, of sulfosalts, and of marcasite and pyrite. There is a chapter on protecting yourself from mineral specimen dangers as well. I browsed it and am happy to have the book (can't you tell).
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Matt Zukowski August 16, 2009 11:34PM
Updated list, perhaps needing reorganization:

Anglesite (brown to colorless)

Anhydrite (blue to colorless)

Apatite (mauve or pink to colorless)
- Pakistan, Afghanistan* pink fades
- La Marina, Mine, Pauna, Boyacá Colombia* pink fades
- Moro Vehlo Mine, Nova Lima, Minas Gerais pink fades
- Himalaya Mine, CA

Aragonite (w/ color)

Argentite

Aurivilliusite

Barite (colorless or blue to darker; blue to colorless; yellow/brown to green or blue)
- “Hartsel” Barite can turn from white to blue in sunlight.
- Moscona Mine barite goes from white to blue in sunlight but reversible.

Beryl v Aquamarine*
- Blue beryl can be made irradiating certain pale natural beryls but like maxime, the electron trap is shallow and so unstable. Fe-colored aquamarines are perfectly stable.
Beryl v Emerald
Beryl v Maxixe* (Blue to colorless or pink)
Beryl v Morganite (apricot or purplish to pink; pink to paler pink)
- One Afghanistan find, pink beryl turned deep yellow with a few hours of sunlight.
- S. CA pegmatites, morganites would be left in the sun to "bring the pink up"

Brazilianite (green to colorless)

Bromargyrite (darkens, Ag liberated)

Calcite (colors fade)
- Elmwood, TN*
- Santa Eulalia (yellow ones from Santa Eulalia temporarily turn pinkish on 15-20 min exposure to sunlight, turn white permanently with 30-60 min exposure to sunlight.

Celestine (blue to colorless)

Chlorargyrite* (gray to violet-brown, Ag liberated)

Cinnabar (red to black metacinnabar)

Corderoite
- McDermitt (Cordero) Mine, NV, Pink Corderoite turns a mouse gray color

Corundum (yellow to colorless)

Crocoite

Creedite (purple creedites are VERY light sensitive)

Cuprite* (darkens, Cu liberated)

Diamond (yellow to green; red to pink)

Djurelite
- Mount Gabriel, County Cork, Ireland

Fayalite (green to blue)

Feldspar v Amazonite*

Fluorapatite (pink fades)

Fluorite (pink to colorless; green to purple; blue or purple to colorless or pink)
- Bingham, NM, blue will fade with exposure to sunlight.
- El Hamman, Morocco, Ink blue pales with 30 min direct sun exposure *
- Elmwood fluorite is reported to be stable.
- Haute-Loire, France, sky blue turns colorless with 30 min direct sunlight.
- Hilton yellow fluorite is reported to be stable.
- Navidad Mine, deep grape purple when mined, but miners put in sun for 6-9 weks to turn them pink.
- Sant Marçal, Montseny, Spain, deep blue turns dirty green with 1 hr direct sunlight exposure. *
- Weardale (Cowshill area), Pale green changed to purple almost immediately on exposure to daylight (not even direct sunlight!).
- Weardale (Rogerly, Heights, Cement Quarry, and the old White's Level), green are all potentially unstable, though to varying degrees. Purple color appears more stable. Deep green fluorite from the Rogerly (Solstice Pocket) permanently changed almost instantly to a muddy gray-green if exposed to a LWUV lamp; this process took longer in sunlight.

Halite (blue or yellow may change)
- Huantajayite (argentian halite, contains silver halides)
- Searles lake, pink color from halophylic bacteria and algae fade with exposure to sun.

Haüyne (blue pales)

Hisingerite (red to brown)

Ianthinite (purple to greenish yellow)

Inesite

Kleinite (yellow to orange)

Lepidolite (purple to gray)

Marcasite (w/ high humidity - can speed up oxidation)

Metatyuyamunite (yellow to green)

Mercury Halides like Aurivilliusite

Miargyrite

Miersite (darkens, Ag liberated)

Mosesite (yellow to green)

Nepheline (pink to colorless)

Orpiment

Pabstite (pink to colorless)

Pararealgar*

Phenakite (red to pink)
- Lemon yellow phenakite from Mt Antero turned colorless after one day in sunshine.
- Orange/brown phenakite from the emerald/alexandrite deposits in the Urals turn colorless or white depending on inclusion content within hours or days if exposed to UV light.

Proustite*

Pyrargyrite

Pyrite (w/ high humidity, light can speed up oxidation)

Pyrostilpnite

Quartz (most colored quartz is light sensitive)
Quartz v Amethyst (fades)
- Brazilian amethyst
- Nebraska amethyst will bleach after a couple of days in the sun.
Quartz v Citrine
Quartz v Morion
Quartz v Rose* (fades)
Quartz v Smoky (smoky to greenish yellow to colorless)
Quartz v Agate
Quartz v Opal

Realgar* (red to yellow pararealgar)
- Realgar is only sensitive to green light

Rutile (pale to darker)

Scapolite (violet to colorless)

Selenite (pink fades)

Silver, native – can tarnish when exposed to light and moisture
Silver Halides (these generally darken and Ag is liberated)
Silver Sulfides/Sulfosalts like Miargyrite

Sodalite (blue)*
Sodalite v Hackmanite* (red to green, blue, or colorless)

Spinel (red)

Spodumene v Hiddenite
Spodumene v Kunzite (pink to colorless)

Stephanite

Tetrahedrite

Topaz* (brown to colorless or blue; blue to paler or colorless)
- Most Thomas Range, UT sherry topaz xtals turn colorless with exposure to sunlight.
- Some topaz xtals from east side of the Thomas Range, UT start out as sherry but turn pink after one to three weeks in the sun. This is due to an unusually high content of pseudobrokite inclusions. The pink is stable, at least after one year of leaving these in the sun.
- Some topaz from the Little Three Mine were collected as colorless but turned blue upon exposure to the sun. Blue crystals that came out of the 1976 and 1991 pockets became much more blue with exposure. This blue color appears stable.
- Sherry colored topaz from Villa Garcia, Zacatecas, Mexico is reported to have stable color.
- The sherry colored portions of topaz xtals from Mokrusha Mine, Urals fade and seem to turn light blue with exposure to sunlight.
- Volodarsk/Volhynsk, Ukraine topazes usually start our dark orange but fade quickly with exposure to sunlight. Bicolored samples found in some pockets (light pinkish champagne and blue) seem to be more stable (at least for 15 years).

Tourmaline (some pink, red)

Tuperssuatsiaite
- Tuperssuatsiaite specimens from Aris started out mauve but turned green.

Vanadinite (red or yellow to darker)

Vivianite (green, blue)*

Wulfenite
- Red Cloud wulfenites will fade over time

Xanthoconite

Zircon (brown)*
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PJ from Maine September 17, 2009 09:14PM
Thank you for this useful list. Last week I purchased a lovely specimen of blue kyanite. Not finding the mineral on this list, I thought nothing of leaving it exposed on a table in front of a large sunny window. It has definitely faded, prompting me to do some belated web research. I found a discussion of the fading of kyanite along with photos at this website...Kyanite - Discussion and photos of fading
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Reiner Mielke September 18, 2009 09:42PM
I have collected a considerable amount of Hackmanite from the Davis Quarry in Bancroft by digging in the waste piles. There are two types of hackmanite, tenebrescent and non-tenebrescent. Both fluoresce bright orange under longwaveUV but the tenebrescent stuff more strongly. The strange thing about it is that the tenebrescent hackmanite is pink when you first dig it out of the ground ( the non-tenebrescent is white) but after taking it home and storing it in the dark in the basement it fades to white. The pink colour comes back if you expose it to shortwave UV or sunlight on days with a high UV index. But putting it back into the dark causes it to fade to white again. Light from a halogen lamp or fluorescent light causes the colour to fade more rapidly but not completely. To get it to fade completely you have to store it in the dark ( takes a few weeks).
If storing samples in the dark at home causes them to fade to white, then why is the freshly dug up stuff pink ( without having hit it )? I will try breaking some faded tenebrescent hackmanite to see if it turns pink. I am thinking that maybe something else is at play here like radioactivity. The dumps at the Davis Quarry have a lot of cyrtolite zircon in them, maybe that is keeping the colour from fading in the dumps? I am also going to store some faded tenebrescent hackmanite with some cyrtolite and some with uraninite (to speed up any possible interaction) to see what happens. Stay tuned.
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Adam Kelly September 19, 2009 07:36PM
I have lots of kyanite, and have never had a problem with fading.
Looks like time to experiment.
First I'll have to get a small piece I can test on.
AK
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Reiner Mielke September 21, 2009 03:27PM
Hackmanite mystery is solved. The faded hackmanite did not regain it's colour when I broke it in half, but the half that I placed a piece of uraninite on became noticeably pink in three days. That would explain why the pink tenebrescent pieces that I dug out of the mine dump ( full of radioactive zircon) turned white in the dark of my basement ( no radioactivity there) . I guess if your hackmanite turns pink in the dark at home you have a radiation problem! I wonder how effective it would be as a dosemeter?
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Jolyon & Katya Ralph September 21, 2009 04:05PM
Correlation does not imply causation. Having radioactive hackmanite in your home also causes your messageboard posts to be sent four times :)

Interesting research, but I think it's a bit hasty drawing your conclusions from it.

Jolyon
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Reiner Mielke September 23, 2009 02:35AM
The uraninite is in the shed, the computer is in the house. I thought the problem of multiple posts was on your end? :) Any suggestions for more conclusive experimentation? Anyone know why some hackmanite changes colour and some doesn't?
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Fred E. Davis September 23, 2009 12:21PM
Before investing effort and time in poorly controlled experiments, try a little internet research. You'll find a variety of answers from the short at Wikipedia to the long at American Mineralogist, and many in between.
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Reiner Mielke September 24, 2009 02:41AM
In everything I have read on the subject it says that if you keep the sample in the dark the colour will return. This does not happen with Davis Quarry Hackmanite, in fact the opposite happens. That leaves me wondering about the reliability of the theories on it. If anyone wants to do some serious experimenting on it let me know and I will send you some samples.
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Rob Woodside September 24, 2009 03:59PM
Reiner You are right I saw this in a paper posted at RRUFFF and was looking for it the other day and got distracted. No one I asked has ever seen the colour return. I wanted to check the internet postings before posting here and properly collect my thoughts. I need to search Tenebrescence and photochromic behaviour. I'm trying to sort out if the pink is created by the extremely large energies at the edge of a forming fracture and if this property is just a long lived phosphorescence.
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Reiner Mielke September 24, 2009 09:35PM
Thank you Rob. I am looking forward to what you find. I broke a piece of tenebrescent hackmanite that had faded to white and the colour did not return not even on the fracture surface, not sure if that is conclusive. I tested the broken surface with SWUV and it turned pink to make sure it broke on a tenebrescent surface.
I know that on the Davis Quarry dumps some large pieces of hackmanite with no coloration on the outside when broken open will have patches of pink inside. These faded to white in the dark of my basement, as does most of the hackmanite from that locality ( I have one piece that started out dark purple which faded to pale pink and seems to have stabilized at that colour). As for getting it to fade in the light, fluorescent and halogen light seems to work best and will cause tenebrescent hackmanite (that has been coloured by short wave UV), to fade quickly but not completely. To get it to lose all it's colour I have to store it in the dark (with the exception of the piece noted earlier).
The other half of the faded tenebresecent piece that I broke in two I placed in the dark with a piece of uraninite on top of it. That piece started to turn pink in about three days. I have left the two together to see how long it will take to completely restore the colour to what SWUV will produce. I suspect it is the gamma radiation that is doing the same thing as SWUV.
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Rob Woodside September 24, 2009 10:32PM
Reiner wrote:
"I have one piece that started out dark purple which faded to pale pink and seems to have stabilized at that colour"

That matches the Afghan experience. Some is quite purple and remains that way and some fades to pink as you observed. I suspect that Gammas and betas just tear hell out of the structure, (like fracturing). Alphas do the same but aren't very penetrating. I have some orange Fiesta ware that Mom served me dinner on for many years as well as Washington Autunite which is also a pure alpha emitter. I'll check with the weak Hackmanite that I have. There seems no radioactives in the Afghan Marbles. (I checked Ladjuar Madan matrix for Sr and it is a marble and not a carbonatite. There is also no apatite, but maybe at Kiran where the good Hackmanites came from. I'll check Kiran matrix) If the pink coloration is due to ambient radiation then the colouration will be present in unfractured material. This is a little like wondering if the refigerator light is on when the door is closed, until you find the switch!!!
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Fred E. Davis September 24, 2009 11:35PM
My experience is with a specimen I field collected from Mont Saint-Hilaire years ago. It was a deep raspberry red when I picked it up. Exposure to white light (including sunlight, incandescent, etc) cause it to fade to white. When exposed to UV (especially SW), it will reset the color back to the raspberry red. The photo below (old & scanned from a print so not the best) illustrates the sequence which can be repeated (as far as I know) indefinitely.

open | download - hack1.jpg (83.3 KB)
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Rob Woodside September 24, 2009 11:56PM
I guess the question that is rattling around in my mind, is does it fade any differently (ie faster) in the light than in the dark. From the little I recall without Googling "photochromic" that is what is supposed to happen.Without proper back up googling I hesitate to ask. If that is right then breaking in the dark and taking half into the light leaving the other half in the dark might tell the tale. Once the piece in the light has faded compare it with the dark piece. If a photo of the two halves showed a noticeable colour difference that would be evidence for light induced colour loss, which I think is what photochromic is supposed to mean. It just seems so bizarre that any light with a UV component causes the colour change and "light" causes it to fade. Tomorrow I'll do the googling.
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Fred E. Davis September 25, 2009 12:23AM
It does not fade in the dark; it always fades in white light - the stronger the light the quicker the fade. I have never read anything about radioactivity having any effect. But hey, it doesn't hurt to look.

For a quick look, I used the hackmanite from MSH shown in the previous photo. For a radiation source, I used a golfball-sized chunk of solid uraninite (>25 mR/hr).

1) I started with the hackmanite white, and put it into intimate contact with the uraninite for ten minutes in the dark. That had no visible effect - no red spots appeared.

2) I exposed the hackmanite to SW UV (6 watt lamp) for five minutes. It turned a dark raspberry red.

3) I put the now red hackmanite in intimate contact with the uraninite for ten minutes in the dark. That had no visible effect - it was still brightly colored, no fading.

As I suspected, radioactivity has no effect (at least in the short term). Light radiation - visible to UV - has an immediate effect (less than five minutes for a complete change in either direction).
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Rob Woodside September 25, 2009 12:59AM
In the stong sunlight of Denver my Afghan Hackmanite colours dark purple then fades in indirect light or dark to a pale pink. But Fred says:

"it always fades in white light - the stronger the light the quicker the fade."
and
"I exposed the hackmanite to SW UV (6 watt lamp) for five minutes. It turned a dark raspberry red."

So your white light has no UV??? What was the white light source you used to test this? Does it fade more slowly in the dark?



Edited 1 time(s). Last edit at 09/25/2009 01:00AM by Rob Woodside.
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