FMF - Friends of Minerals Forum, discussion and message board

[John S. White]

My amethyst after a month in the sun (in Pennsylvania!) The pieces were once attached. The one on the left is the piece exposed to the sun, the other is my control piece kept in the dark.

[Ed Huskinson]

Oh, I see John.
These are the trimmin's from your "owl eyes" in/on amethyst that you posted a little while ago. Good material to work with. So you'll post a photo for comparison every now and again? I like it! We could even help. A six-month exposure to Arizona summer sunlight should prove interesting, maybe even bake it to citrine, eh? This is a good experiment. I'm sure Les Presmyk will volunteer to put the amethyst up on his rooftop for a while sometime after Tucson 2010, maybe return it at the following Denver show, if it should survive the stultifying Phoenix heat.

In the meantime, we can periodically follow it's progress there in the Pennsylvania sunlight. You might have to bring it inside for the winter though....

Hope Denver was good to you.

Later,

Ed

[John S. White]

Hi Ed:

It is my intention to leave it out for quite a long time, the ice and snow will not really harm it. Your suggestion of passing it on to Les is a good one and I will consider it. Certainly the Arizona sun will prove a better test than what we get here.

Denver was a fine show, as usual, and I managed to add one single crystal to that part of my collection and four very nice quartzes to my quartz collection. Will try for some photos.

[Jordi Fabre]

[John S. White]

My amethyst has been out in the sun for three months now and there is no perceptable change in color when directly compared with the control sample.

[Antonio Alcaide]

Hi all,

After some time and while we wait the results of the experiment John is carrying out, why not trying to refine all your contributions to the light sensitive minerals list. Give me a couple of days to read the thread completely and I will be able to suggest you a simple way to make a short list with only the minerals most of you consider light sensitive ("A" list). The rest of the above mentioned minerals we can put into another "B" list: low level of sensitivity).

Of course the target is to shorten the list in order to make it useful. I suppose that knowledge based on your own experience will be better (than rumors, readings, etc).

At the end I have explained what I pretend. But, please, give me a bit of time.

Regards

[Jordi Fabre]

Good idea Antonio, is the way to make useful this thread!

If finally we can build two reliable lists of light sensitive minerals, then I will publish both lists in a special post to be used as a reference and, as agreed, I will submit them to Mindat as well as to the Spanish Forum (translated)

I wait for more news, I were disappointed for the current status of this exciting thread, so thanks for the initiative.

Jordi

[Antonio Alcaide]

Come on.

First of all, I think I am speaking in everybody's name thanking Matt his efforts in this thread to make a comprehensive list of all the light sensitive minerals. I hope not to bother him or anybody starting from his excellent work. We all can make a list of actually light sensitive minerals including the rest -minerals under suspicion- on another list. I suggest one short "A" list and a complete and detailed "B" list with the rest.

Thanks, Jordi for your support and encouragement.

We can use the Matt's final and complete list located on the page number 2 in this same thread. I don't think it necessary to reproduce the list here. Please, send me via mp or publish in a new post your short list with only the minerals you have the experience or knowledge of undergoing changes in sunlight. I will adding your contributions to an agreed list trying to make a short one. As mentioned above, the rest of minerals (whose light sensivity is discussed) will appear on the large "B" list.

During the process I will ask your amendments and corrections to the list.

When in doubt please do not include the species on your short list. It is a very important topic, so let's work hard and do a good job.

Regards,
Antonio

[alfredo]

John, your amethyst hasn't changed colour because there's hardly any sunshine in Pennsylvania. You should bring it out here to Palm Springs, California, and watch it fade while you get darker (yes, we should add Homo sapiens to the light-induced colour changes list ;))

More seriously, shouldn't brown topaz be on the list too? I only know the ones from Thomas Range, Utah, and Tanakamiyama, Japan, but both of those are very light sensitive and will invariably lose their brown colour on exposure. Other localities - I'm not sure.

On the other hand, I disagree about rose quartz - not sensitive to light at all.

Chalcocite: Is this really a light-induced change? Or just exposure to air? I think chalcocites often alter even in the dark.

Vivianite: I wrote an article once claiming that ALL vivianite is light-sensitive, but then a Canadian curator wrote in disagreement, claiming that the vivianite from Big Fish river, Yukon, was stable. At first I did not believe this, but on comparing chemical analyses of vivianites from around the world I notice that Yukon vivianite is much lower in the unstable Fe(II) than other vivianites, with about a third of its Fe atom positions filled by Mg instead, so perhaps it's true that Yukon vivianite is more resistant to light than others.

[Jordi Fabre]

I would move to the list 'B' the following especies:

Aragonite (w/ color)
Celestine (blue)
Corundum (yellow)
Crocoite
Diamond (various colors)
Pink halite from Searles lake is colored by halophylic bacteria and algae that fade with exposure to sunlight.
Inesite
Quartz (most colored quartz are light sensitive)
- Amethyst (especially Brazilian amethyst)*
- Citrine
- Morion
- Rose Quartz*
- Smoky Quartz
- Various Agates
Opal
Scapolite (violet)
Sodalite (blue)*
- Hackmanite (salmon/pink)*
Spinel (red)
Spodumene
- Hiddenite
- Kunzite
Tourmaline (some pink, red)
Wulfenite
Zircon

[Jason]

does anyone know if the Ouro Prêto purple topaz is color stable?

[Jordi Fabre]

I believe they are color stable.

Jordi

[arturo shaw]

Hi

I've take a look to "The Care and Conservation of Geological Material" by Frank M. Howie and try to find more minerals concerned but the list coincides with that from Matt.

What I knew about the Spodumene was that it turns pink into Kunzite not the opposite, but I can be wrong....

Rusian brown topaz is very light sensitive.

Greetings

Arturo

[Antonio Alcaide]

Here I am. Following the last Jordi's suggestion, I have moved the species he mentions to the B list.

Please, contribute to refine the A list, the original Matt's list located on page 2. It is still so long.

B list. Minerals less light sensitive

Aragonite (w/ color)

Celestine (blue to colorless)

Corundum (yellow)

Crocoite (red to brownish)

Diamond (various colors)

Pink halite from Searles lake is colored by halophylic bacteria and algae that fade with exposure to sunlight

Inesite (redish to whitish)

Quartz

- Amethyst (especially Brazilian amethyst)
- Citrine
- Morion
- Rose Quartz
- Smoky Quartz
- Various Agates
- Opal

Scapolite (violet)

Sodalite (blue)

- Hackmanite (salmon/pink)

Spinel (red)

Spodumene

- Hiddenite
- Kunzite

Tourmaline (some pink, red)

Wulfenite

Zircon


Regards

[John S. White]

Closing in on 6 months in the sun, my amethyst has yet to show any loss of color. However, there have been days when it was obscured from the sun by a coating of another mineral, subsequently removed through careful treatment with a broom.