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Field CollectingLight Sensitive Mineral List
6th Nov 2008 14:30 UTCPeter Hargis
Thank you.
7th Nov 2008 03:45 UTCAlfredo Petrov Manager
7th Nov 2008 04:10 UTCSteve Hardinger 🌟 Expert
7th Nov 2008 05:56 UTCKnut Eldjarn 🌟 Manager
7th Nov 2008 06:19 UTCNH
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
7th Nov 2008 08:54 UTCjacques jedwab
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
ie Sodalite, var: Hackmanite..
7th Nov 2008 09:28 UTCPeter Haas
7th Nov 2008 11:13 UTCKnut Eldjarn 🌟 Manager
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
- Rockservation
*LIST HAS BEEN MOVED FURTHER DOWN TO MORE RECENT POSTS*
7th Nov 2008 21:05 UTCSteve Hardinger 🌟 Expert
8th Nov 2008 09:29 UTCRay Hill Expert
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
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
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
9th Nov 2008 01:50 UTCRay Ladbury
9th Nov 2008 10:37 UTCRay Hill Expert
9th Nov 2008 16:57 UTCPeter Hargis
LIST HAS BEEN MOVED EVEN FURTHER DOWN
9th Nov 2008 18:10 UTCAnonymous User
Philippe.
9th Nov 2008 18:24 UTCDaniel Russell
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
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
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
11th Nov 2008 07:23 UTCKnut Eldjarn 🌟 Manager
Knut
11th Nov 2008 08:27 UTCNH
11th Nov 2008 11:52 UTCRock Currier Expert
11th Nov 2008 12:37 UTCAlexander Ringel
i believe, that most colors are unstable, which cames from natural radioactive treatment.
Greets
Alexander
11th Nov 2008 18:17 UTCNH
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
14th Nov 2008 16:51 UTCDaniel Russell
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
14th Nov 2008 17:04 UTCKnut Eldjarn 🌟 Manager
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
> 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
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
22nd Dec 2008 17:59 UTCEddy Vervloet Manager
Is that also the influence of light?
20th Apr 2009 16:59 UTCRick Sinclair
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
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
Cheers,
Alfredo
20th Apr 2009 23:16 UTCAmir C. Akhavan Expert
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
Bob.
21st Apr 2009 15:36 UTCPeter Hargis
23rd Apr 2009 20:29 UTCAdam Kelly
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
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
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
10th Jul 2009 01:12 UTCAdam Kelly
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
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
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
11th Jul 2009 23:11 UTCPeter Lyckberg Expert
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
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
Jolyon
12th Jul 2009 17:09 UTCDavid Von Bargen Manager
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
13th Jul 2009 03:37 UTCJim Bean 🌟
13th Jul 2009 15:13 UTCPeter Hargis
27th Jul 2009 05:31 UTCMatt Zukowski 🌟
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
Cuprite*
27th Jul 2009 12:09 UTCRock Currier Expert
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
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
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 🌟
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 🌟
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
18th Sep 2009 21:42 UTCReiner Mielke Expert
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
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
21st Sep 2009 16:05 UTCJolyon Ralph Founder
Interesting research, but I think it's a bit hasty drawing your conclusions from it.
Jolyon
23rd Sep 2009 02:35 UTCReiner Mielke Expert
23rd Sep 2009 12:21 UTCFred E. Davis
24th Sep 2009 02:41 UTCReiner Mielke Expert
24th Sep 2009 15:59 UTCRob Woodside 🌟 Manager
24th Sep 2009 21:35 UTCReiner Mielke Expert
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
"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
24th Sep 2009 23:56 UTCRob Woodside 🌟 Manager
25th Sep 2009 00:23 UTCFred E. Davis
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
"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
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
25th Sep 2009 01:20 UTCFred E. Davis
25th Sep 2009 13:06 UTCReiner Mielke Expert
25th Sep 2009 16:20 UTCFred E. Davis
26th Sep 2009 01:45 UTCReiner Mielke Expert
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
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
> 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
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
As far as I can tell this change is permanent!!!
27th Sep 2009 01:28 UTCReiner Mielke Expert
27th Sep 2009 06:35 UTCRob Woodside 🌟 Manager
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!!!
A 10 minute exposure to UV makes it pretty dark purple
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
Now the tungsten source exposed Hackmanite is given another 10 minute UV exposure to restore the purple colour
Now the UV exposed Hackmanite is left in the dark for 2 hours and only some of the purple fades
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
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
27th Sep 2009 20:39 UTCReiner Mielke Expert
27th Sep 2009 21:15 UTCFred E. Davis
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
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
6th Oct 2009 16:17 UTCJan Styer-Gold
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
6th Oct 2009 17:46 UTCAnonymous User
7th Oct 2009 06:17 UTCAnonymous User
28th Feb 2010 01:10 UTCAdam Kelly
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
28th Feb 2010 21:14 UTCAdam Kelly
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.
1st Mar 2010 02:50 UTCRock Currier Expert
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
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
2nd Mar 2010 20:43 UTCRob Woodside 🌟 Manager
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
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
3rd Mar 2010 08:06 UTCRock Currier Expert
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
31st Dec 2014 10:09 UTCAntoine Barthélemy Expert
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
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
"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
31st Dec 2014 14:36 UTCReiner Mielke Expert
31st Dec 2014 16:09 UTCJakub Jirásek Expert
31st Dec 2014 16:32 UTCRob Woodside 🌟 Manager
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 UTCturtledove thrushe
2nd Jan 2015 00:34 UTCAlfredo Petrov Manager
2nd Jan 2015 02:07 UTCDoug Daniels
2nd Jan 2015 02:12 UTCturtledove thrushe
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> 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
2nd Jan 2015 03:03 UTCturtledove thrushe
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> 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
3rd Jan 2015 17:31 UTCRock Currier Expert
13th Mar 2016 18:15 UTCSans
13th Mar 2016 19:13 UTCAlfredo Petrov Manager
1st Jul 2017 20:54 UTCRobin Ball
1st Jul 2017 21:04 UTCReiner Mielke Expert
1st Jul 2017 21:08 UTCAlfredo Petrov Manager
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
24th Oct 2019 20:22 UTCTama Higuchi Manager
28th Nov 2019 12:10 UTCThomas Lühr Expert
That's really a good one :)
Thanks Tama ... and Jolyon of corse!
2nd Jul 2017 02:41 UTCRobin Ball
2nd Jul 2017 04:38 UTCAlfredo Petrov Manager
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
16th Sep 2018 19:01 UTCAsh Sierra
28th Nov 2019 14:29 UTCKevin Hean
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
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
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 Manager
18th Oct 2020 13:46 UTCGary Morse
18th Oct 2020 02:52 UTCJulie Wilson
I have a specific question about vanadinite, specifically San Carlos Vanadinite.
I know some vanadinite is light stable but most isn’t.
It has been suggested that the Mexican vanadinite is not light sensitive. I know I have seen many examples in brightly lit displays with what appears to be no change in color. But, I am still hesitant without confirmation from experts.
We recently got a large parcel of vanadinite with a wide range of colors and hues ranging from yellow to red to dark brown and I believe there was even some black.
So, can anyone confirm if some or all San Carlos Vanadinite is light stable?
If some pieces are then would the entire parcel be?
My guess is that the answer is, some is and some isn’t. That it varies by piece and the only real way to tell is to put it in the light and hope.
I had to ask just in case I’m wrong.
Thanks for any and all help.
19th Oct 2020 09:47 UTCKeith Compton 🌟 Manager
I have always assumed (rightly or wrongly) that any red mineral containing lead will fade.
26th Nov 2020 06:37 UTCErin Rose Latta
26th Nov 2020 12:07 UTCAlfredo Petrov Manager
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Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: May 9, 2024 23:21:49