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Preparing a list of light sensitive minerals - (14)
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Matt_Zukowski
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PostPosted: Jul 09, 2009 23:49    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

Another question is, if I am the editor, where is a good place I can maintain a document that i can work on and others can see and/or edit? This way i can get feedback as I assemble. I don't know what resources are available for collaboratively building a document.

Jordi - i guess we should do it on whatever website has some sort of collaborative facility where we can all work on a master document.
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PostPosted: Jul 10, 2009 00:10    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

One more question - David - have you considered and discarded the idea of setting up a true wiki that would allow every registered mindater to add and or edit info for the article? Seems to me like this is quickest and easiest way to assemble a comprehensive article.
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PostPosted: Jul 10, 2009 07:33    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

Matt,

Here we have a complicate question. If you leave the "door open", then a lot of incorrect details could be added to the draft, or some accurate info could disappear due the action of other members changing it. I believe that in Mindat they restricted the "free pass" to everybody due the number of incorrect details they got at the start of the web page.
Don't mention the spammers, always flying up popular web pages, trying to introduce their pieces of shit (excuse me ;-)

For me, it will work well a thread where everybody could explain his thoughts via new posts, with the editor guiding the process, and when ready, summarizing the final conclusions.

If you wish to do it here, I can create an specific area named "Collaborations with Mindat" or something like this, where the thread of the "List of the sensitive minerals" would be located, and at the end of the process, it could be offered to Mindat to be implemented in its own work (if they want it).

If you prefer to prepare it directly in Mindat, fine, this is your decision. Just letting us know.

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PostPosted: Jul 10, 2009 11:17    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

Mindat is really just one big wiki, albeit with some very specific entry areas and crosslinks. There are three major areas with different controls and people who can enter things. The most open is the locality and mineral list area. Here, most registered users can edit entries. In the mineral pages, entry is pretty much limited to managers since these are areas where there is usually one right entry for the property (and where checking to make sure things are right takes about the same amount of time as entering the data itself). The source for these entries is also of a bit of importance - you don't want the properties to come from "The golden Book of minerals". The third area is the photographs and in general we find that photographers don't like to have their descriptions edited. Over the years, we have developed easy ways to keep track of what is getting entered and backing out problem entries.

With a free for all wiki, you get the criticism that no one takes responsibility for the entry being accurate. We also get comments like - Why should I work long and hard on a subject only to have some yahoo come along later and mess it up.

We had a classical wiki for the site manual and we were getting spammed quite a bit so we just closed it off, just allowing a few authorized users.

The article system was set up so that only one (or a select group of people the main author trusted) would control the content. Other registered users can post comments on the articles, so the editor is free to add these comments in. We are also doing something similar with Rock's "Best Minerals" project in the messageboard. If you wanted to get input from people who aren't registered, you could set up a link to a thread on the messageboard where they could post comments. The articles can be kept private (the author can supply the link to others if he wants, or the article can be "published", allowing anyone to view the article).
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PostPosted: Jul 13, 2009 09:38    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

I got the software updated so you can enter any special handling required. On the locality/mineral level, this can be edited on the detail page (clicking the i icon or stars from the locality page bring up this page). This data is also displayed on the main mineral page - at least after the cache is cleared. The data can also be entered on a mineral basis (ie silver halides) by those with sufficient editing rights.

Thanks for bringing up this enhancement.

For examples see the mercury or topaz pages.
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PostPosted: Jul 16, 2009 19:48    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

David:

I cannot add any info to the locality/mineral pages. I am registered and logged in. The only thing i can find about adding information is a line at the bottom of the page that says:
If you would like to add information to improve the quality of our database, then click here to register. When i click the link, I go to my registration page.

I am unclear about how to setup an article in mindat. I will try to figure out a way to send you a PM either here or in mindat and we can discuss this further if you want without burdening the readers of the board with all these posts. When something gets figured out, I will give the group a progress report.
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PostPosted: Jul 17, 2009 03:39    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

To add data to mindat, you have to have your account "activated" - request access (I went in and did that). To get to an edit page for a mineral at a locality, on the locality page, you need to click on the i icon or star after the mineral name. You will then get the detail page brought up and can get to the edit page from there.

The article can be started from your home page (you want the article, not blog)
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PostPosted: Jul 26, 2009 23:35    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

I pulled together a bunch of info from mindat and FMF and am posting it here and on mindat. I think I understand how the article feature works in mindat and may being an article on mineral care there. Hope this moves the ball forward a reasonable amount.

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 Morro Velho Mine, Nova Lima, Minas Gerais.
- Himalaya Mine, CA
Aragonite (w/ color)
Argentite
Aurivilliusite
Baryte (blue)*
- “Hartsel” Baryte 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*
Cinnabar
- 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)
Djurleite (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*
- Smoky 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:
https://minerals.caltech.edu/COLOR_Causes/ (link normalized by FMF) and any mineralogy textbook.



Knut's suggestions for avoiding harmful effects of light:
1. For as much time as possible keep the minerals in a closed box or drawer.
2. Avoid exposure to direct sunlight and strong daylight.
3. Avoid the combination of strong light, heat, moisture and reactive fumes like sulfur.
4. Keep your display room dark when not in use.
5. The most safe light source would be an IR and UV-depleted source transmitted by fiberoptics (also to avoid exposure to heat).
6. An IR and UV-depleted light source with a color-spectrum in the visible part of the spectrum balanced as in natural sunlight/daylight would have the potential of creating the most "natural" colors.
7. For especially unstable colors, exposure to the same wavelengths corresponding to the color of the object would result in a very low absorption of light and thus less fading would be expected.
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PostPosted: Jul 27, 2009 10:38    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

I am puzzled by the inclusion of Brazilian amethyst. Both in Tucson and in Denver Brazilian geodes sit out in the intense desert or mountain sun for a week or more and I am sure that if they changed the dealers would not do this, unless they change in a positive way, which I do not believe to be the case.

Additionally not all light induced changes are negative. Some Illinois fluorite, I have been told, are very dark and almost black when first mined so they are placed in the sun to improve (lighten) their colors.

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PostPosted: Jul 27, 2009 12:32    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

Great job Matt!. Now we can use the list as a draft to include on it new additions. If you don't care you can wait for all new additions and prepare a new list when not more posts arrive?

Let me add to the details mentioned for John these other ones:

- Pink Apatites from La Marina, Mine, Pauna, Boyacá Colombia *
- Baryte from Moscona Mine, Solís, Asturias, Spain turn white to blue with sun light and if a long term exposition (weeks) them return to white.
- Ink blue fluorite from El Hamman, Morocco, pales with 30 min direct sunlight exposure *
- deep blue Fluorite from Sant Marçal, Montseny, Spain, turn to dirty green with 1 hour direct sunlight exposure. *
- Vanadinite turn its red color to brown after a long term exposure to sunlight *

Is much more that we can add to the list, I'm sure that other people will also help adding still more details.

Thanks again for your efforts Matt!

Jordi

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PostPosted: Jul 27, 2009 14:54    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

Hi John and all,

Indeed, Brazilian amethyst does lighten in color when kept in direct sunlight for prolonged periods. The change may not happen or be noticeable after a week or so, but my sources routinely tell me a different story if the amethyst is exposed for say one month or more.

Rock Currier even talks about this in his recent MR articles.


Cheers,

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PostPosted: Jul 27, 2009 15:14    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

Rock also talks about amethyst fading at https://www.mindat.org/forum.php?read,5,115692,116035#msg-116035

Roger Pabin mentions that amethyst from Nebraska will bleach after a couple of days in the sun. So it does seem as if amethyst from some localities can react slower or faster to sunlight.
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PostPosted: Jul 27, 2009 16:09    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

These discussions are good. John, I think it is good to add data on minerals that are not affected or are improved by exposure to light. You will see in the list mention that Hilton yellow and Elmwood fluorite appear to be light stable and that Morganites from various S. CA pegmatites would be left in the sun to "bring the pink up."

John - can you more specific on what IL fluorites improve with exposure - if so, I'll add it.

Anyone who can critique anything in the list or any way to add to the list is encouraged to do so.
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PostPosted: Jul 29, 2009 04:26    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

Sorry Matt, that was something told to me many years ago and I do not know the specific source names.
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PostPosted: Jul 29, 2009 09:59    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

The octahedral fluorites from the Navidad Mine in Rodeo Durango are deep grape purple when mined, but the commercial dealers leave them in the sun for 6-9 weeks until they turn an attractive shade of pink.
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PostPosted: Jul 29, 2009 10:22    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

Fluorite from a over 1m3 pod enclosed in skarn, with fine grained molybdenite mineralization as a rim around (in the skarn) had a deep violet color when collected by me at the 220 m level of Yxsjöberg Cu-Scheelite deposit in Sweden in december 1977. The fluorite would luminesce after hitting it with a sledge hammer, or by shining on it closely by the head light, or at home from heating it in hot water.
After a couple/few years it turned a light sky blue color (stored in garage with no direct sunlight but N facing window), and after additional years it turned entirely white, which almost no geologist or collector could distinguish from quartz (NO, no obvious cleavaged!). Beeing white it had lost all its luminescent properties.
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PostPosted: Aug 06, 2009 00:23    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

I just 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.

What i will do is, over the next week or two, read the book and update this thread on light sensitive species with the intention of getting the info on the internet without rehashing the book. What the book lacks is locality specific information - that is always welcome - so if you can think of anything please post it and I will accumulate everything and post it here and on mindat.

Please note that Howie, 1992 also includes information on thermal and humidity sensitivity, and includes chapters on the special sensitivity of elements, of sulfides, of sulfosalts, and of marcasite and pyrite. There is a chapter on protecting yourself from mineral specimen dangers as well. I browsed it and am happy to have the book (can't you tell).
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PostPosted: Aug 06, 2009 01:56    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

That's just wonderful! It will be a fantastic job Matt, thanks a lot.

As soon as I have time, I will add new additions to the list.

Jordi

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PostPosted: Aug 16, 2009 17:26    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

The Howie book is excellent. 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.
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PostPosted: Aug 16, 2009 17:27    Post subject: Re: Preparing a list of light sensitive minerals - (14)  

Updated list, perhaps needing reorganization:

Anglesite (yellow and brown to colorless)

Anhydrite (blue to colorless)

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

Aragonite (w/ color)

Argentite (darkens)

Aurivilliusite

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

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 (red to brownish)

Creedite (purple creedites are VERY light sensitive)

Cuprite* (darkens, Cu liberated)

Diamond (yellow to green; red to pink)

Djurleite
- Mount Gabriel, County Cork, Ireland

Fayalite (green to blue)

Feldspar v Amazonite*

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.

Gypsum (pink fades)

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 (redish to whitish)

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 (darkens)

Miersite (darkens, Ag liberated)

Mosesite (yellow to green)

Nepheline (pink to colorless)

Orpiment (slow decay)

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* (darkens)

Pyrargyrite (darkens)

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

Pyrostilpnite (darkens)

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)

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) -> fades

Spodumene v Hiddenite (fades)
Spodumene v Kunzite (pink to colorless)

Stephanite (darkens)

Tetrahedrite (darkens slowly)

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 and red fades)

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

Vanadinite (red or orange to darker)

Vivianite (green, blue) -> decay*

Wulfenite
- Red Cloud wulfenites will fade over time

Xanthoconite (darkens)

Zircon (brown) -> fades*
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