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A general guide for using the Forum with some rules and tips
Sensitive minerals
  
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chris
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PostPosted: Oct 24, 2008 12:51    Post subject: Sensitive minerals  

Les presmyk said:
>Tracy, just remember to keep the cinnabar in a box when you are note viewing it and it will remain this color forever.

Hi Les,

I'm very interested by your comment about keeping cinnabar in the box. I thought it was less light sensitive than realgar for instance. Does it mean the color might be altered by long term light exposure ?

If so, do you know what the consequence would be ? As a sulfide collector a nice cinnabar is on my wishing list. But as I prefer to keep my specimens on display (not in a box) I would like to know the consequence(s) of my choice before doing it.

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Christophe
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Les Presmyk




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PostPosted: Oct 24, 2008 13:19    Post subject: Re: Sensitive minerals  

All cinnabar will darken with exposure to sunlight. It is not the same as realgar where there is a chemical change that takes place. So, keeping cinnabar, like proustite or pyrargyrite, in a box will keep the color red. Actually, I have seen realgars that have been out of the ground and kept in the dark that are as red today as they were 50 years ago when they were collected.
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Jordi Fabre
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PostPosted: Oct 25, 2008 05:03    Post subject: Re: Sensitive minerals  

>All cinnabar will darken with exposure to sunlight.

Right, I don't mentioned it before, assuming that this it is something well know, so it is very useful for me to discover that is not, and that next times I should remember to mention it, not only concerning the Cinnabar but also about all other minerals sensitive to the light or the humidity.

On the other side I'm sorry to disagree with Les. The Realgar is sensitive not only to the light but also to the humidity. Les live in a very dry place, so not doubts about the stability of Realgars well preserved of the light on a so dry places, but in Barcelona, for example, or in other places with high humidity, the Realgars decay, also on the darkness.

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chris
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PostPosted: Oct 25, 2008 13:42    Post subject: Re: Sensitive minerals  

Hello Jordi,

Won't it be useful to create a new thread about this subject ? Sulfides aren't the only minerals which are light sensitive. And it is not always easy to get such information, especially for a beginner.

For instance In France you can find beautiful sky blue fluorite from Haute-Loire... Unfortunately a 30 min direct sunlight exposure turns it colorless ! I know it because I'm French, but how a foreigner would know about it ? And I'm sure you could easily name Spanish examples.

Christophe
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Jordi Fabre
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PostPosted: Oct 25, 2008 14:36    Post subject: Re: Sensitive minerals  

Done Chris. Thanks for your suggestion.

BTW, pink Apatites are also sensitive to the light (them becomes paler). At least the ones from Kazakhstan, Colombia, and less, Pakistan.

Jordi
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alfredo
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PostPosted: Oct 25, 2008 20:38    Post subject: Re: Sensitive minerals  

A curious fact of no great importance: realgar is only sensitive to green light! So if you filter out the green and only expose it to the rest of the spectrum, its decay will be much less rapid. I don't know whether anyone has ever done this in a display - I suppose you could put it in a glass case illuminted only with a red light bulb.
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Druid




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PostPosted: Oct 26, 2008 02:51    Post subject: Re: Sensitive minerals  

Another reason that cinnabar should be kept in a box is due to the fact that it is a mercury based mineral and in hot weather mercury vapors can be released. i have been told to keap mine in a sealed transparent box for viewing purposes.
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Jordi Fabre
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PostPosted: Oct 26, 2008 03:17    Post subject: Re: Sensitive minerals  

But this would be suitable only if you have native Mercury on the specimen, because the Cinnabar is highly stable and it don't release mercury at all in hot weather.
The Chinese Cinnabar, for example, have not Mercury on its Dolomite matrix.

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Tracy




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PostPosted: Oct 26, 2008 10:20    Post subject: Re: Sensitive minerals  

For there to be any serious risk of being exposed to mercury, I imagine one would have to be surrounded by continuously vapor-releasing specimens in a room with no air circulation (invoking Paracelcus: the dose makes the poison). Surely there is much less mercury in a single cinnabar-mercury specimen than in an old-fashioned thermometer? Even if I am wrong, keeping the windows open in hot weather should give sufficient protection... :-)
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PostPosted: Oct 27, 2008 00:39    Post subject: Re: Sensitive minerals  

Thank you for the correction there folks. that is one of the reasons i am here. to learn :)
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PostPosted: Oct 27, 2008 08:41    Post subject: Re: Sensitive minerals  

Jordi, I do not take your comment as disagreement. I was not aware that moisture contributes to the degradation of realgar as well. When one lives in an area that averages less than 19cm of rain a year, we do not deal with humidity related issues. Also, topaz is a mineral that needs to be kept out of direct sunlight, especially those from Utah and Pakistan.

Blue fluorites from Bingham, New Mexico, USA will fade as well. None of this is meant to alarm anyone, just to be cautious. You would have to heat up cinnabar far beyond room temperatures, even in Arizona, to get any off gasing of mercury.
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alfredo
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PostPosted: Oct 27, 2008 10:12    Post subject: Re: Sensitive minerals  

I agree with you, Les and Tracy. The public tends to assume that if a mineral contains a poisonous element, the mineral must be dangerous. I know a collector who won't buy arsenopyrite crystals because "they contain arsenic, and I have children at home". He doesn't realize his children could hurt themselves more severely by cutting themselves with a broken quartz crystal than anything the arsenopyrite is likely to do to them!

And some of the "not quite so poisonous elements" can actually be WORSE for children, if swallowed. An azurite specimen, swallowed, will be more poisonous than an arsenopyrite, just because it's more soluble in our stomach juices.

Cheers,
Alfredo
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