FMF - Friends of Minerals Forum, discussion and message board

[John S. White]

"PS: Jim, I do not understand very well your words: "toss that out". Do you mean to rule it out, not to consider it at all?"

Good point Antonio. I suspect that some contributors to these threads forget that the FMF enjoys a very large international audience, many of whom are not native English speakers. So slang terms and phrases like "toss that out" can be very confusing and can also diminish the substance of the message. Therefore, I would urge native-English-speaking contributors to avoid as much as possible using terms and phrases that are not reasonably clear to all visitors to the Forum. This also goes for abbreviations, such as N.C., instead of North Carolina.

[John S. White]

No further changes in the amethyst color after nine months.

[Peter Megaw]

Given the improvement of the amethyst color through fading of the smoky component, I am sure mineral dealers will put this to good commercial use.

Any chance you could verify teh UV effect by putting a piece of the control material under a high intensity UV light for extended perioids of time?

[John S. White]

Will give it a try.

[Snowman]

I have a question about light sensitive minerals.

Can the colour of water soluble minerals also be affected by the sunlight alone? I ask this because i was once working in the Andes (5200m) along the Argentinian/Chilean border on the Argentinian side (San Juan Province). I came across some copper sulfate minerals(Cant find the name) that were sitting in the shade. After about a few days i decided to collect some and once they were in the sunlight their colour faded within an hour. I was told that exposure to air makes them loose their colour but i observed that while they were under the shade they retained their colour. I was told that sunlight had nothing to do with it. Was it a combination of exposure to the air and sunlight that cause the colour fading? Even in the sun the air was very cold at the time the picture was taken. Can anyone verify this?
Thanks in advance.

[ellencmoe]

This is a great topic.

My experience is very limited - mostly with pegmatite specimens from San Diego County, California, US.

Beryls can develop color when exposed to sun. I left a bucket of chunks of what I assumed were quartz in my yard. A few months later, one piece on top had developed a very nice aquamarine color. Unfortunately, a nice crystal from the 49-er pocket which is pale aquamarine on one corner, mostly colorless in the center, and pale peach morganite on the far corner, did not develop better color even when left in the sun all summer.

Spodumenes are also affected by sunlight, although I am not sure they always lose color. Kunzite has the nickname "The Evening Stone" since it may fade if exposed to sunlight/UV light. The pieces of spodumene I find on the old tailings from the Pala Chief Mine tends to be totally lacking color. But, the owner of the Oceanview Mine, also on Chief Mountain in Pala, California has experimented with some pieces of spodumeme he has been finding in abundance the last few years. A few of the beautiful purple Kunzites he left in the sun did not lose color. He also tried putting sunblock (sun tan lotion on pieces). The Oceanview Mine website www(dot)digforgems(dot)com may still have the results of his tests.

[Carles Millan]

[Maxilos]

I think this is a great topic for starters, and especially if they don't know everything about their specimens.

Mark

[Riccardo Modanesi]

Hi!
From the photos of the (at present) two amethyst specimen I can't appreciate so big a difference in color! Maybe by seeing these specimen truly and not through a picture, the difference would be clearer.
Greetings from Italy by Riccardo.

[Olivier]

Out of curiosity, did this list ever see the light of day? (pun intended)

[James Catmur]

Good question - I am not sure it did. If needs someone to scrape the thread and then compile it

[James Catmur]

Asking an AI tool I got this response, with a few locality comments:

Here are some minerals known to be sensitive to light:

Apatite: Certain pink variants from Pakistan and Afghanistan exhibit light sensitivity.
Aragonite: This mineral, especially when it has color, can be light-sensitive.
Argentite: A silver mineral that may react to light exposure.
Calcite: Some calcite specimens from Elmwood, Tennessee, are sensitive to light.
Corundum: Yellow corundum (sapphire) can be light-sensitive.
Diamond: Various colored diamonds may exhibit light sensitivity.
Fluorapatite: Pink fluorapatite is known to be sensitive to light.
Fluorite: Numerous colors of fluorite can react to light.
Halite: Blue and yellow halite crystals may be light-sensitive.
Mercury Halides: These compounds containing mercury should be kept away from light.
Pyrostilpnite: A mineral that can be sensitive to light.
Sodalite: Blue sodalite may exhibit light sensitivity.
Spinel: Red spinel can react to light exposure.
Spodumene: Green spodumene may be sensitive to light.
Topaz: Brown, sherry, and blue topaz can be light-sensitive.
Tourmaline: Some pink and red tourmaline varieties may react to light.
Vivianite: Green and blue vivianite can be sensitive to light.
Xanthoconite: A mineral known for its light sensitivity.
Zircon: Brown zircon may react to light exposure.

Remember that sensitivity can vary based on specific localities and conditions. Proper care is essential to preserve the beauty and stability of these minerals.

[alfredo]

"Blue sodalite"? The AI seems to have messed up. At La Fuente, in Tucson, we've had barrels of blue sodalite from both Bolivia and Brazil siting out in the burning Arizona sun for years, with no change at all.

The hackmannite variety of sodalite, on the other hand, is extremely light sensitive, changing color in mere seconds, but that isn't blue.

[Jordi Fabre]

And Argentite is a not existing mineral, at least at a human temperature 😏

[Peter Lemkin]

list-in-progress [some repetition; some need more explanation.....

Apatite (pink from Pakistan, Afghanistan)
Aurivilliusite
Barite (blue)
Beryl (maxixe emerald)
Morganite
Bromargyrite
Calcite (from Elmwood, TN)
Aragonite (w/ color)
Celestine (blue)
Cinnabar
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)
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)
------------------------
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 out 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)*