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Field CollectingLight Sensitive Mineral List

6th Nov 2008 14:30 UTCPeter Hargis

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.

7th Nov 2008 03:45 UTCAlfredo Petrov Manager

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....

7th Nov 2008 04:10 UTCSteve Hardinger Expert

Kunzite and morganite

7th Nov 2008 05:56 UTCKnut Eldjarn Manager

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.

7th Nov 2008 06:19 UTCNH

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.

7th Nov 2008 07:09 UTCJohn Sobolewski Expert

Pink Corderoite from the Cordero and McDermitt Mines turns a mouse grey color when exposed to light. John S.

7th Nov 2008 08:54 UTCjacques jedwab

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.

7th Nov 2008 09:03 UTCRay Hill Expert

Light sensitive might also be applied to reactions/changes when exposed to light,


ie Sodalite, var: Hackmanite..

7th Nov 2008 09:28 UTCPeter Haas Expert

Not to forget about fluorite.

7th Nov 2008 11:13 UTCKnut Eldjarn Manager

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...

7th Nov 2008 15:13 UTCPeter Hargis

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*

7th Nov 2008 21:05 UTCSteve Hardinger Expert

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.

8th Nov 2008 09:29 UTCRay Hill Expert

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...

8th Nov 2008 11:38 UTCKnut Eldjarn Manager

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.

8th Nov 2008 22:26 UTCRay Hill Expert

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 .

9th Nov 2008 00:41 UTCRock Currier Expert

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.

9th Nov 2008 01:50 UTCRay Ladbury

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.

9th Nov 2008 10:37 UTCRay Hill Expert

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

9th Nov 2008 16:57 UTCPeter Hargis

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

9th Nov 2008 18:10 UTCAnonymous User

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.

9th Nov 2008 18:24 UTCDaniel Russell

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 )

9th Nov 2008 18:46 UTCDaniel Russell

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

10th Nov 2008 20:31 UTCPeter Hargis

*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)

11th Nov 2008 06:44 UTCAnonymous User

is Krohnkite light sensitive, i have it in a small glass box within a glass display case with a 40 watt bulb.

11th Nov 2008 07:23 UTCKnut Eldjarn Manager

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

11th Nov 2008 08:27 UTCNH

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).

11th Nov 2008 11:52 UTCRock Currier Expert

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.

11th Nov 2008 12:37 UTCAlexander Ringel

Hello,

i believe, that most colors are unstable, which cames from natural radioactive treatment.

Greets

Alexander

11th Nov 2008 18:17 UTCNH

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.

14th Nov 2008 13:51 UTCAlfredo Petrov Manager

How did red spinel and pink tourmaline get on the list? Seem pretty stable to me.

14th Nov 2008 16:51 UTCDaniel Russell

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. "

14th Nov 2008 16:55 UTCDaniel Russell

A gemologist friend commented to me recently that cuprite was light sensitive. I have seen no documentation of this... anyone have any information?

14th Nov 2008 17:04 UTCKnut Eldjarn Manager

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

14th Dec 2008 10:07 UTCClaus Hedegaard

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

14th Dec 2008 12:28 UTCKnut Eldjarn Manager

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

16th Dec 2008 00:51 UTCAnonymous User

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.

22nd Dec 2008 17:59 UTCEddy Vervloet Expert

What about the pic of the day for 22 december?

Is that also the influence of light?

20th Apr 2009 16:59 UTCRick Sinclair

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

20th Apr 2009 18:12 UTCPeter Hargis

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.

20th Apr 2009 22:20 UTCAlfredo Petrov Manager

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

20th Apr 2009 23:16 UTCAmir C. Akhavan Manager

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

21st Apr 2009 00:50 UTCRobert Rothenberg

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.

21st Apr 2009 15:36 UTCPeter Hargis

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.

23rd Apr 2009 20:29 UTCAdam Kelly

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

23rd Apr 2009 20:51 UTCPeter Hargis

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...

9th Jul 2009 15:39 UTCPeter Lyckberg Expert

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.

10th Jul 2009 00:58 UTCAlfredo Petrov Manager

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.

10th Jul 2009 01:12 UTCAdam Kelly

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

10th Jul 2009 20:12 UTCPeter Lyckberg Expert

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.

11th Jul 2009 00:22 UTCAdam Kelly

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

11th Jul 2009 16:51 UTCAnonymous User

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.

11th Jul 2009 23:11 UTCPeter Lyckberg Expert

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

12th Jul 2009 16:54 UTCRob Woodside Manager

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!!!

12th Jul 2009 17:02 UTCJolyon Ralph Founder

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

12th Jul 2009 17:09 UTCDavid Von Bargen Manager

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).

12th Jul 2009 17:13 UTCRob Woodside Manager

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.

13th Jul 2009 03:37 UTCJim Bean

Excellent addition, David!

13th Jul 2009 15:13 UTCPeter Hargis

Awesome, thanks for the addition!

27th Jul 2009 05:31 UTCMatt Zukowski

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.

27th Jul 2009 08:43 UTCJolyon Ralph Founder

Add to the list:


Cuprite*

27th Jul 2009 12:09 UTCRock Currier Expert

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.

27th Jul 2009 18:48 UTCPeter Hargis

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.

5th Aug 2009 17:03 UTCKeith Corrie

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

16th Aug 2009 23:33 UTCMatt Zukowski

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).

16th Aug 2009 23:34 UTCMatt Zukowski

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)*

17th Sep 2009 21:14 UTCPJ from Maine

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

18th Sep 2009 21:42 UTCReiner Mielke Expert

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.

19th Sep 2009 19:36 UTCAdam Kelly

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

21st Sep 2009 15:27 UTCReiner Mielke Expert

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?

21st Sep 2009 16:05 UTCJolyon Ralph Founder

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

23rd Sep 2009 02:35 UTCReiner Mielke Expert

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?

23rd Sep 2009 12:21 UTCFred E. Davis

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.

24th Sep 2009 02:41 UTCReiner Mielke Expert

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.

24th Sep 2009 15:59 UTCRob Woodside Manager

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.

24th Sep 2009 21:35 UTCReiner Mielke Expert

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.

24th Sep 2009 22:32 UTCRob Woodside Manager

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!!!

24th Sep 2009 23:35 UTCFred E. Davis

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.

24th Sep 2009 23:56 UTCRob Woodside Manager

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.

25th Sep 2009 00:23 UTCFred E. Davis

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).

25th Sep 2009 00:59 UTCRob Woodside Manager

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?

25th Sep 2009 01:03 UTCFred E. Davis

I use a flashlight (mini-maglite), desklamp, etc. The sun's down right now so I can't repeat a sunlight exposure. I recall trying a He-Ne laser to see if a long wavelength would fade it, but as I recall, it did not.


A 60-watt bright-white CFL effected a complete fade in about 15 seconds.


A 60-watt soft-white CFL (with more red & less blue) caused a partial fade in about 15 seconds, and a nearly complete (but not full) fade in one minute. This is consistent with the He-Ne laser test. So, it takes short wavelengths to fade, and even shorter (UV) to recharge.

25th Sep 2009 01:14 UTCRob Woodside Manager

Thanks Fred. Those are Tungsten sources with not a lot of UV. At St Hilaire I found these pink rocks that blanched even in direct sunlight. I'll check my Hackmanite in Direct Sunlight now at the 49th parallel. I'll see if I can check this with my Hackmanite. I've got a laser pointer and maybe I'll spring for a second desk lamp.

25th Sep 2009 01:20 UTCFred E. Davis

I think we may have crossed messages. Sorry, no more edits to the old message. If I have further info to report, it'll be in a new message. Let me know what you find! Curiosity killed the cat, but satisfaction brought him back!

25th Sep 2009 13:06 UTCReiner Mielke Expert

When I experimented with radioactivity and hackmanite I noticed no change for the first 48hrs, try exposing your sample longer and make sure it is in the dark. When I got my samples of Hackmanite home from the Davis Quarry I went to wash them in the sunshine and expected the colour to fade instead it got more intense. I then went into the house and got a sample from an earlier trip that had faded and when I held it in the sun it turned pink-purple. The only conclusion I could come to is that on high UV index days the effect of the UV overcomes the negative effect of the other wavelengths. On cloudy days or days with low UV index this does not happen. It is also possible that hackmanite from different sources behaves differently.

25th Sep 2009 16:20 UTCFred E. Davis

If I can get results in 15 seconds with visible and UV light, and the effects of radioactivity take 172,800 seconds or more, then radioactivity must not be a major contributor to tenebrescence.

26th Sep 2009 01:45 UTCReiner Mielke Expert

Hello Fred,


In the short term I would agree. It has been a week now and the specimen has not noticeably darkened any more. However, on a scale of years it may have a significant effect. How else can one explain the brightly coloured tenebrescent hackmanite that one finds buried deep in the waste piles at the mine, but that turn white in the dark of one's basement. After all water doesn't noticeably dissolve limestone in 15 seconds but we all know that doesn't prove anything.

26th Sep 2009 02:05 UTCRob Woodside Manager

Minoscam has a great set of articles:

http://www.minsocam.org/MSA/AmMin/TOC/

but sadly you can't copy exerpts.


Medved in 1954 wrote about tenebrescence and hackmanite in:

Edit: http://www.minsocam.org/ammin/AM39/AM39_615.pdf

and mentioned that Robert Allen in his 1834 Manual of Mineralogy first reported it. However mineralogists being sensible people knew that was silly and ignored it for nearly 100 years. This tradition, of which I am guilty, seems to have plagued the field ever since, Medved also reported that Lee in 1901 observed both the darkening and the bleaching when exposed to light in the wavelength ranges 2280- 4800 A and 4800- 7500 A respectively. Medved goes on to say, "The peak efficieciency of bleaching occurs at wavelengths shorter than yellow. Following reversal there is some partial recovery of colouration if the specimen is kept in the dark for more than five weeks." Using simple ideas of band theory and F centres he concocts a simple model to explain these features from his observered absorption spectra.


A year later Kirk in:

http://www.minsocam.org/ammin/AM40/AM40_22.pdf

repeats the story that after fracturing Hackmanite fades quickly in daylight and "The pink colour returns when the mineral is kept in the dark for a few weeks." Kirk's real contribution was to realize that the were two absobtion bands one at 5300 A and one at around 5800 A. Medved had found the latter and the former which hid in it is really an F center and said to be responsible for sodalite's blue colour. An F centre occurs when ionizing radiation knocks a negative ion out of its lattice site and a single electron falls into that hole. So if that is the case then ambient radiation is responsible for sodalite's blue colour.Kirk also gives good information on fluorescence and heat bleaching. His primary conclusion is to finger sufur as the colouring agent!!! It gets better.


RRUFF is also an excellent source for literature. Sadly some journals are caught in the internet squeeze and won't let RRUFF post them but below the specimen descrption you can click on the "view file" and see those that do, The Canadian Mineralogist is one that does and in 1979 they published:

http://rruff.info/uploads/CM17_39.pdf


Blue Sodalite by Annersten and Hassib drops the claim about the colour returning in the dark. They give some good heating data and dispose of Medved's F theory for the 5800 absorbtion. They observe fogginess in blue sodalite, an improved conductivity for blue sodalite over heat bleached sodalite. and a free single electron spin resonance. From these data the conclusion is obvious!!! The blue colour is due to colliodal particles of metallic sodium!!! Nevermind the F centres!!! I'm surprised the referee didn't ask them to insert a warning that sodalites could prove a fire hazzard on washing with water!!! So the tradition begun by mineralogists in 1834 has been well honoured down the years and most recently by me thinking that tenebrescence was just a long lived phosphorescence. I'd be intersted in hearing about any further work done in the last thirty years.

26th Sep 2009 10:10 UTCFred E. Davis

> How else can one explain the brightly coloured tenebrescent hackmanite that one finds buried deep in the

> waste piles at the mine, but that turn white in the dark of one's basement.


They formed with the bright color, and are bleached when exposed to white light. That seems self evident.


There's another interesting discussion in "Fluorescence: Gems and Minerals Under Ultraviolet Light" by Manuel Robbins, Geoscience Press, 1994, ISBN 0-945005-13-X. There are a variety of expressions of tenebrescence, and effects vary. Note in particular on p. 131:


"Most researchers appear to agree that F-Centers are the cause, or at least part of the cause, of reversible color in hackmanite. The term F-Center comes from the German word farbe, which means "color." F-Centers are responsible for coloring a variety of minerals, including fluorite and barite. In hackmanite, it is proposed that some of the negatively charged chlorine atoms are missing. A negative electric charge is required at such vacancies to provide charge balance, and any free electrons in the vicinity become drawn to such vacancies and are trapped there. Such a trapped electron is the typical basis of an F-Center. It appears that this center in hackmanite absorbs green, yellow, and orange light and varying amounts of blue. When the hackmanite is seen in white light, red and some blue are returned to the eye, giving the hackmanite colors. It is likely that sulfur, as double negatively charged disulfide units S22-, is the source of the electrons. When ultraviolet is directed at the sodalite, it is absorbed at disulfide units. These each lose an electron and thus become S21- units. The free electrons wander to the chlorine vacancies where they are trapped, coloring the mineral."

26th Sep 2009 19:17 UTCRob Woodside Manager

Thanks Fred. Yes our posts crossed during edit and I'm surprised that your CFL didn't have enough UV to over come the bleaching. Yellow starts at roughly 5900 A and 4800 A is well into the green, almost blue. These are the wavelengths Medved says are best at bleaching. The wavelength or colour of course gives you the energy available (photon) for mucking about with the electronic structure and the intensity of the light tells you the sum of these available energies. So I suspect that the difference caused by your CFL sources arose more from intensity rather than wavelength.


I don't think this is a finished story yet. What you quote from Robbins seems to me the kind of sensible story containing several truths that I fall into, defend vigorously, and then realize that reality is a little more complicated. My recent posts on agates, nepheline, and dauphine twinning are good examples, in case anyone is counting. One problem here is that colours are often determined by minute traces of things that are undetectable with standard methods. I have several probe spectra (EDS) of colour changing Hackmanites that detect no sulfur. Certainly polysulfide is responsible for the ultramarine of Lazurite and this suggests to people that sulfur may have a role in Sodalite/Hackmanite. It may. However in spite of their peccadillo of Native Sodium, Annersten and Hassib show that the absorption at 5300 A is a F centre and supposedly responsible for Sodalite's blue colour, whereas the much broader absorption at 5800 A is not an F centre and seems responsible for the fading pink colour of hackmanite. Yet both are caused by ionizing radiation. All sodalites can be heat bleached to a grey white that can be recoloured by ionizing radiation. So finding a grey white sodalite means either that it experienced high temperature or there was insufficient ionizing radiation present to colour it. As James Hutton pointed out so long ago, the same tiny changes occurring over vast times can produce large changes and Reiner is quite right about waiting long enough to see radiation induced changes in Hackmanite. Until these absorption bands in sodalite/hackmanite are completely understood I don't think anything is certain.


I don't know if Medved introduced the word tenebrescence, but he says it comes from the Latin tenebrae for shadows and has a diagram to explain it. The formating gets screwed up on posting so I'll describe it. He starts with a clear xl and bombards it with x-rays, electrons, etc. that turn it into a coloured xl and then reverses the colour change with exposure to heat, light etc. So this tenebrescence is very broad and would include thermoluminescence etc. Today the preferred term is photochromic which as far as I can find merely means a reversible colour change caused by light. This narrows things somewhat and would seem to include fluorescence, phosphoresence, and darkening or bleaching caused by light. The new sun glasses darken in the presence of light and bleach in its absence, but hackmanite actually darkens in UV rich light and bleaches in visible light!!!

26th Sep 2009 19:42 UTCRob Woodside Manager

0758487001253989875.jpg
To back up my claim that some gemmy blue sodalites darken on UV exosure, here's the proof:







As far as I can tell this change is permanent!!!

27th Sep 2009 01:28 UTCReiner Mielke Expert

I am repeating my experiment with uraninite. This time I have a control sample. I found two pieces of bleached hackmanite of approx. equal tenebrescence ( you can determine this with long wave UV because tenebrecent hackmanite fluoresces more brightly than non-tenebrescent hackmanite). See attached photos. I then wrapped one with a piece of uraninite in lead sheet and the other by itself in aluminum foil and placed them about 20cm apart. I am now going to wait for a couple weeks and then photograph the two samples again to see if there is any colour change. I am betting that there will be a colour change in the sample with the uraninite. Stay tuned.

27th Sep 2009 06:35 UTCRob Woodside Manager

0957203001254023148.jpg
Thanks Reiner. I hope your Uraninite is a bloody hot Precambrian one and that the hackmanite turns blue in a few weeks!!! However it may take much longer for anything to happen. The question that is driving me nuts is whether the hackmanite that shows fading pink on fracturing is actually pink on the inside??? I suspect it is not and the pink colour is actually caused by the fracturing. I don't know of any stong chemicals that would strip the surface faster than it would fade, but a chemist might suggest how to quickly chemical mill hackmanite. If it really is due to the fracturing then if two pieces of bleached pink fading hackmanite were bashed or harshly rubbed together fracturing powder from the surface then we should see some pink in the powder This would be triboluminescence that happens with some quartz and sphalerites. Could you please try that and tell us what happens?



Here's a picture of my hackmanite that has dark adapted for over 6 months and contrary to Medved's report has not recovered any of it pink color.








Fred says his St Hilare Hackmanite fades in sunlight. Here's what happens to my dark adapted Hackmanite with a 10 minute exposure to direct sunlight. It clearly doesn't fade!!!


00014200014951481731095.jpg
Dark adapted Hackmanite after a 10 minute direct sunlight exposure





A 10 minute exposure to UV makes it pretty dark purple


00679440014951481731023.jpg
Purple Hackmanite caused by a 10 minute UV exposure






This purple Hackmanite was then left under a Tungsten source for 2 hours and it bleached considerably. Now it is only slightly pinker than the dark adapted example


01495030014951481738423.jpg
After 10 minute UV exposure and then 2 hours under a tungsten source.





Now the tungsten source exposed Hackmanite is given another 10 minute UV exposure to restore the purple colour


02239980014951481734366.jpg
After bleaching the purple Hackmanite returns with a 10 minute UV exposure





Now the UV exposed Hackmanite is left in the dark for 2 hours and only some of the purple fades


02993730014951481739175.jpg
Faded colour after a 2 hour dark adaption





From these data one can conclude:


1) Exposure to ultra violet rich light causes very slowly fading absorption bands that don't absorb the pink/porple colour of this Hackmanite


2) The destruction of these adsorption bands be speeded up by exposure to light poor in ultra violet

27th Sep 2009 19:44 UTCReiner Mielke Expert

Hello Rob,


I will powder a piece of faded tenebrescent hackmanite in the dark and let you know what happens. Have to be carefull not to powder it too much, since it has a white streak, even bark blue sodalite powders white. My Davis quarry hackmanite behaves the same as your St.Hilaire stuff. So much for the darkening in the dark theory. The last time I experimented with uraninite/hackmanite there was a noticeable colour change after 3 days so three weeks should produce a good result. The challenge will be photographing it, I will have to do it in the dark with a flash. Good thing it doesn't fade instantaneously or we would be caught in the fridge door light conundrum.


Reiner

27th Sep 2009 20:10 UTCReiner Mielke Expert

Just a thought. Maybe the tenebresecent coloured hackmanite is " born" (formed) coloured and exposure to any light destabilize this primary colour causing it to fade in the dark from that point on. However I still think that radioactivity is what colours it so that once you take it away from a radioactive source it fades in the dark. That would mean that if I break open a large faded chunk of hackmanite that has been in my basement for a long time it should be white inside. When I broke open large chunks at the quarry they were coloured inside. I will try smashing open a large faded chunk (11kg) that I have and see if it is coloured inside. Hate to do it though after lugging it 4km on my back so I could have a big piece, oh well I'll do it in the name of science.

27th Sep 2009 20:39 UTCReiner Mielke Expert

Broke open the large chunk and it was coloured on the inside (that is at the core but white from the outside to a depth of about 5cm). Originally when I found it it was coloured on the outside. My head is starting to hurt! 8-) If the force of fracturing induces a colour wouldn't one expect the colour to be all along the fracture surface and not just at the core? If radioactivity preserves the colour why didn't it fade evenly in the dark when taken away from the radioactive source ( in the Davis Quarry that would be radioactive zircons). At this point the only thing that fits this data is the birth-colour destabilization theory. In otherwords since the core of the sample has never been exposed to light of anykind the colour is stable. However since the outside has been exposed to light ( it would seem to a depth of 5cm) the colour is not stable and fades in the dark. Anyone else have an explanation?

27th Sep 2009 21:15 UTCFred E. Davis

I took a quick peek at the spectrum of the bright-white CFL, and found strongest peaks around 5500 A and 6300 A. There are less intense peaks around 4400, 4900, 6000 and 6600 A.


Manuel Robbins suggests the range 4800 to 7200 A is best for bleaching.


As with many things, there's a lot of wiggle room. :)

27th Sep 2009 21:20 UTCReiner Mielke Expert

Hello Fred,


Thanks for the info, I found that CFLs work well for bleaching but you still have to keep the sample in the dark afterward to get it to bleach completely, at least for Davis Quarry stuff.


Reiner

27th Sep 2009 21:25 UTCFred E. Davis

Yup, Robbins mentions a lot of variability. Some do, some don't. Go figure...

6th Oct 2009 16:17 UTCJan Styer-Gold

Here's another one to add to the list:


Chrysoprase (Chalcedony) (light green to apple green)


The color of chrysoprase can fade in sunlight and when heated. The color may return if the specimen is kept under moist storage away from light.


Jan

6th Oct 2009 17:23 UTCAlfredo Petrov Manager

With regard to the chrysoprase (and other chalcedony varieties); This is probably not a true colour change, but rather decreased transparency caused by evaporation of interstitial water in micropores. The colour "returns" when you get it to absorb water again.

6th Oct 2009 17:46 UTCAnonymous User

Pink Halite from Searles Lake. Sunlight kills the salt loving bacteria that cause the pink colour.

7th Oct 2009 06:17 UTCAnonymous User

Tourmaline is not photosensitive. Tourmaline is typically heat sensitive, and the color can be lightened by exposure to intense heat. This is usually done to tourmaline that has been artificially irradiated to produce a dark red color, which then can be heated to lighten the hue, and produce a lighter hued reddish pink. Heat treatment can also be performed on dark bluish green tourmaline to lighten the hue. Heat treatment, however, is not the same thing as photosensitivity. I am unaware of any tourmaline species fading from exposure to near infrared, visible, or ultraviolet light - which includes examples that have been artificially irradiated and/or heated to change the color. The color center is always stable. The only portion of the electromagnetic spectrum that has an effect on tourmaline is gamma rays and x-rays, and this exposure causes a increased saturation of color, versus fading, or desaturated color.

28th Feb 2010 01:10 UTCAdam Kelly

Does anybody know?

Is the fluorite from Riemvasmaak, Northern Cape Province, South Africa prone to fading in sunlight?

This local is sometimes called Orange River also.

AK

28th Feb 2010 03:48 UTCRock Currier Expert

It may be since this is a relatively new locality that there has not been enough time pass yet for it to be known if the color will fade yet. If a dealer gets an exciting new find of a mineral, usually one of the bottom of the list things he wants to do is to take matching pieces of the mineral and place one of them in strong sunlight for a month so he can report on any color fading. There is no financial upside in this sort of experiment, only a potential down side. If however a competitor starts a roomer that the color is not stable, which happens quite often, so as to hopefully dampen the sales of a competitor, then such a text will be done as quickly as possible so that damage control can be instituted.

28th Feb 2010 21:14 UTCAdam Kelly

Thanks Rock,

Thats pretty much what I figured.

My girlfriend works in a rockshop.

Her boss just brought back a few pieces from Tucson.

The front window in the shop gets lots of sun, and thats where they are right now.

It's worth it to me, just to help preserve minerals in their prime condition.

Thanks,

AK

1st Mar 2010 00:03 UTCLuiz Alberto Dias Menezes, Fo.

One of the most dangerous minerals in terms of color decaying under light is pink apatite; my experience with pink apatites from at least 2 Brazilian localities (Morro Velho gold mine and Golconda mine) is that under sunlight the pink color fades completely in no more than 30 minutes. At the 2008 Sainte Marie aux Mines show I lost several specimens because the sides of my tent get exposed to sun-light and so I was trying to keep the flat with the pink apatites away from it but customers handle the flats back and forth and somebody moved it to the wrong place so in minutes the pieces lost the pink color.

1st Mar 2010 02:50 UTCRock Currier Expert

Luiz,

I was once told that these apatites can be irradiated and made pink again. I have also experienced some color loss with my Morro Velho apatites even though they have mostly been kept in the dark.

2nd Mar 2010 19:13 UTCAlexandra Catalina Seclaman

Someone said amethyst is light sensitive?


I have a piece since i was born and it has the same color, and it gets a lot of light.

2nd Mar 2010 20:25 UTCRock Currier Expert

The amethyst from Rio Grande do Sul and that from Artigas Uruguay are slowly light sensitive. The fading is not something that is immediately apparent, but if you put them out in direct sunlight for six months, the fading is very obvious. All the guys who work with amethyst at those two localities know this and I have run exposure tests on specimens from both localities. I have not run tests on amethyst from other localities, but I suspect that amethyst from other localities will also fade. To test the amethyst from a locality you need two more or less identical specimens. One you put in a dark place and the other you put out in your garden for a few months and at the end of the time you compare the two specimens. Very simple. But who wants to do these tests when the best you can discover is that the specimens from a locality will not fade. Since I have never heard any amethyst suppliers boast that their amethyst is stable, I assume that if such tests have been made, the results have shown that the amethyst fades and that fact is kept quiet.

2nd Mar 2010 20:43 UTCRob Woodside Manager

Somewhere I saw a photo of an amethyst xl specimen that had be broken in half and re-assembled. One half was a satisfying dark amethyst and the other half a sickly weak amethystine quartz. One half had been left in full sunlight for sometime and the other half kept out of direct sunlight.


I would be surprised if some amethysts lightened and others did not. I rather suspect that the darkest ones lighten at a slower rate

2nd Mar 2010 21:35 UTCRock Currier Expert

Rob,

That would probably be the picture of a specimen of amethyst from Rio Grande do Sul that I made and was published in Gems and Gemology showing a specimen of amethyst that I broke in half. One half I put in the sun for about six months and then glued back together with the piece that had been in a dark box for the same length of time.

2nd Mar 2010 22:50 UTCRob Woodside Manager

Rock, that was a great photo of a very sick rock. ( BTW I hope your Tucson cold is better now. Luckily I seem to have escaped its clutches) If you have access to that photo, could you possibly post it here?

3rd Mar 2010 08:06 UTCRock Currier Expert

Bob,

Im sure glad you didn't get my cold and managed to escape the clutches of the Tucson International Viral Distribution Center. Usually I don't manage to escape. But its all better now and I am back working hard to try and finish the scanning in of the balance of my specimen images. Then I will have the tedious job of photoshoping them all in preparation to uploading them to Mindat. Just took delivery today on my second batch of compressed air in a can (30 bottles at about $100). This should see the job of blowing the dust of the slides to an end. Do you know anyone else who has spent $200 just to blow the lint off their specimen images? Sometimes I think I feel reality slipping away from me.


I took a quick look for that image of the two tone amethyst, but could not locate it. It should be here somewhere in my 50 to 100 K 35mm slides, but other than mounting a month long search effort I think I will just wait till it shows up. When it does, Ill put it in the article I just finished about amethyst.

14th Jun 2011 21:23 UTCEdgars Endzelins

Anyone knows if lorandite is light sensitive? I recently aquired one and noted that crystals on back side of specimen shows more luster but on front side are rather dull...

31st Dec 2014 10:09 UTCAntoine Barthélemy

I am somehow disappointed by the large number of species listed on page 4 in this topic. Also, although nothing new was posted here for quite a long time, I am always afraid that species I have on display will once appear on such a list.


So here is my question: are there really light insensitive species ? Azurite, dioptase or pyromorphite (for instance) are never listed as light sensitive minerals. Does it mean that I can let them on my shelves (sometimes exposed to sunlight) without any harm ? Or would you think that it is anyway better to have the display shelves kept in the dark ?

31st Dec 2014 10:37 UTCAlfredo Petrov Manager

I wouldn't worry about it too much, Antoine. The list you refer to has about 70 species on it (out of the 5,000 or so known mineral species), and for most of those 70 species it is only certain varieties that suffer in the light, not all samples of the species. And some of the things on the list I simply do not believe at all... blue sodalite, light sensitive? Not in my experience - I've had blue sodalite in a sunny window for 20 years and it's still blue.


There are of course some species I would not display in bright light: several noriously sensitive silver and mercury minerals, realgar, vivianite, coloured topaz, purple apatite, amethyst... and a few more, but I'd probably only have 30 species on the list rather than 70.

31st Dec 2014 13:34 UTCReiner Mielke Expert

Hello Rock,


"my second batch of compressed air in a can (30 bottles at about $100). This should see the job of blowing the dust of the slides to an end. Do you know anyone else who has spent $200 just to blow the lint off their specimen images?" Wouldn't it have been cheaper to buy an air compressor?

31st Dec 2014 14:24 UTCDavid Von Bargen Manager

"Compressed air" is most often tetrafluoroethane. When you use an air compressor, unless you filter it, you will just be blasting dust in the air at your photos. You might also be adding some lubricating oil to the air stream.

31st Dec 2014 14:36 UTCReiner Mielke Expert

Yes I would recommend filtering it. The big advantage to compressed air is not only cost but you can use the compressor for other things when you aren't blowing away dust.

31st Dec 2014 16:09 UTCJakub Jirásek Expert

Also many hydrated sulfates, since light means energy convertible to heat.

31st Dec 2014 16:32 UTCRob Woodside Manager

Alfredo, the recently found gem blue sodalites with Wurtzite become darker and turbid underv UV

http://www.mindat.org/photo-253461.html

The usual translucent blue sodalite from everywhere else is either totally stable or has already darkened.

1st Jan 2015 19:29 UTCVitaliy

Is Russian Cuprite (particularly from Rubtsovskoe Cu-Zn-Pb deposit, Rudnyi Altai, Altaiskii Krai, Western-Siberian Region, Russia) also affected especially the ones that backlight red? I was under the assumption it was for the more translucent red Cuprite crystals encountered from other localities.

2nd Jan 2015 00:34 UTCAlfredo Petrov Manager

In the case of cuprite, is the darkening really a light-stimulated change, or is it a tarnish caused by reaction with traces of sulphur in the air?

2nd Jan 2015 02:07 UTCDoug Daniels

Alfredo - possibly a combination of the two?

2nd Jan 2015 02:12 UTCVitaliy

Alfredo Petrov Wrote:

-------------------------------------------------------

> In the case of cuprite, is the darkening really a

> light-stimulated change, or is it a tarnish caused

> by reaction with traces of sulphur in the air?


Has darkening actually been proven to occur on Cuprite's especially those from Rubtsovskoe. I haven't actually seen any actual evidence or facts that show Cuprite darkening from that locality. I can understand it possibly occurring on Translucent Red Crystals from other localities.


The darkening itself has been rumoured to be caused by exposure to either Sulphur in the air (from decomposing Pyrite crystals was mentioned) or simply the exposure to UV or daylight.

2nd Jan 2015 03:00 UTCAlfredo Petrov Manager

Inside houses, there is always some sulphur in the air, even without the presence of pyrite. Cooking eggs, cabbage and other vegetables in that family, city air pollution, and... ahem... (how to put this delicately?) sulphur-bearing vapours emitted by homo sapiens and their domesticated animals... = tarnishing of silver and copper minerals.

2nd Jan 2015 03:03 UTCVitaliy

Alfredo Petrov Wrote:

-------------------------------------------------------

> Inside houses, there is always some sulphur in the

> air, even without the presence of pyrite. Cooking

> eggs, cabbage and other vegetables in that family,

> city air pollution, and... ahem... (how to put

> this delicately?) sulphur-bearing vapours emitted

> by homo sapiens and their domesticated animals...

> = tarnishing of silver and copper minerals.


How much of it is present compared to decomposing or decaying Pyrite that we might have in our collections. I would think that a decaying Pyrite would give off more Sulphur than simple background 'sulphur' if we can call it that. There are also other minerals that decompose and produce Sulphur as a result.


I personally don't mind tarnished copper or silver. I feel it gives it an older 'old world' look to it.

2nd Jan 2015 16:44 UTCRob Woodside Manager

Why isn't the black that forms on all cuprite, just tenorite? Has anyone analysed the scuzz?

3rd Jan 2015 17:31 UTCRock Currier Expert

Yes, it might have been cheaper to buy a compressor, but when I started the job I had no idea of how much compressed air it would take and by the time I did, it didn't seem worthwhile to fool around with a compressor,hook it up and then have an extra hose running into my office plus a switch to turn it on and off when I needed it and then to wait for the pressure to build up. It was faster to just be able to pick up a can close at hand and work with it. I figure the electricity and especially the time saved was worth the expense. I didn't even have to buy a compressor. I could have just taken one from my place of business as I had several extra ones. I also din't like the idea of having one making noise all the time hammering away to fill its little tanks. Then there was the problem that I would have to probably filter that compressed air and periodically drain water from the tanks and maintain the damn thing.

13th Mar 2016 18:15 UTCSans

Hi, I just recently purchased a beautiful specimen of dioptase and a specimen of aragonite from northern lights mine nevada and I was wondering if anyone could help me figure out if they are light sensitive? I took a look at the list but I am unsure if my aragonite qualifies as colourless or not.

13th Mar 2016 19:13 UTCAlfredo Petrov Manager

Shouldn't be any problem with either dioptase or colorless aragonite.

1st Jul 2017 20:54 UTCRobin Ball

List of photosensitive minerals please so I know what stones to keep out of the sunlight. Besides rose quartz.

1st Jul 2017 21:04 UTCReiner Mielke Expert

A follow up on the Davis Quarry hackmanite. My hackmanite specimens have changed their habit? Now they behave like normal hackmanite in that they retain their color in the dark but fade in the sunlight? Seems the material only exhibits the opposite reaction for a limited number of times. Very strange.

1st Jul 2017 21:08 UTCAlfredo Petrov Manager

"Besides rose quartz."

Robin, normal rose quartz (the massive kind) is one of the minerals that is not light sensitive; only the crystals of rose quartz (aka "pink quartz") will fade in the light.

And keep in mind that light sensitive minerals won't only fade in sunlight, but in artificial light as well, albeit perhaps slower since the light is usually less intense.

2nd Jul 2017 00:05 UTCJolyon Ralph Founder

I had a light-sensitive mineral list, but it faded.

24th Oct 2019 20:22 UTCTama Higuchi

Sorry to revive an old post, but this joke needs to be applauded :-)

28th Nov 2019 12:10 UTCThomas Lühr Expert

LOL   Hahaha  
That's really a good one :)
Thanks Tama  ... and Jolyon of corse! 

2nd Jul 2017 02:41 UTCRobin Ball

List of photosensitive minerals please so I know what stones to keep out of the sunlight. Besides rose quartz.

2nd Jul 2017 04:38 UTCAlfredo Petrov Manager

amethyst, colored topaz, realgar, kunzite, purple apatite...


plus many silver and mercury minerals (eg: proustite, chlorargyrite, and many more, although most of them are rare and you probably don't have any anyway)

2nd Jul 2017 22:24 UTCStuart Herring

Some fluorite's like Blanchard NM

16th Sep 2018 19:01 UTCAsh Sierra

Does anyone know about spirit/cactus quartz exposure to sunlight?

28th Nov 2019 14:29 UTCKevin Hean

Hi Ash
It does fade as does  Amethyst, especially if left in direct sunlight.
Another one I found that faded rather quickly was blue calcite from Port Shepstone Natal South Africa. I was told when we were collecting at the quarry that it was coloured by carbon dioxide and that it would fade. 

28th Nov 2019 00:01 UTCZach Berghorst

I'm not sure if anyone is still keeping tabs on this thread or if there is a more official list somewhere else, but it doesn't look like anyone has mentioned Phosphovanadylite-Ca yet. 
According to its Mindat page, it will fade from blue to green to black in prolonged sunlight. I'm wondering if Phosphovanadylite-Ba suffers from the same light sensitivity as well.

28th Nov 2019 12:20 UTCKeith Compton Manager

The Friends of Minerals Forum has a topic that contains lists of numerous light sensitive minerals and some text references:


Searching articles such as those on museum curation of minerals can often provide useful references.

We probably should create a reference article - perhaps I'll start one ?

28th Nov 2019 17:53 UTCTama Higuchi

I think an easy-to-access article including a photosensitive list of minerals needs to be made.  It gets difficult to try and peruse through a messy thread!  
 
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