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How to minimize Arsenic on Realgar
  
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Roxanne Hicklin




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PostPosted: May 17, 2013 11:56    Post subject: How to minimize Arsenic on Realgar  

I manage a collection of a private collector. This specimen is one of his favorites, and he wants it on display. The Realgar continues to form arsenic, and we have been washing it off to get rid of the arsenic and allow the red of the Realgar to show again.
We realize light is causing the problem, but in order for it to be on display, light has to be present. The owner has suggested we coat the Realgar with a coating to seal it and perhaps the arsenic wouldn't form, thinking it might be caused by the air, and not the light. My fear is if we do that, not only will the arsenic continue to form, but we would no longer be able to clean it because it would be sealed.
Are there any suggestions for how to deal with this specimen and continue to display it, minimizing the effects of the arsenic?



Realgar.jpg
 Description:
Realgar on Calcite
Shimen Mine, Hunan Province, China
9x12x6
 Viewed:  27010 Time(s)

Realgar.jpg



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alfredo
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PostPosted: May 17, 2013 12:54    Post subject: Re: How to minimize Arsenic on Realgar  

Roxanne, The yellow stuff that's forming is not arsenic, it's a mineral called pararealgar. You are quite right that the change is caused by light (mostly by green light), and coating it is not going to help. Light-sensitive minerals should be kept in the dark. Perhaps the collector could dedicate one display case just for the light-sensitive minerals, and cover that case with a black sheet or something to block the light, and viewers could just lift it up temporarily to look at the rocks? Putting it in a red glass box (to cut out the green wavelengths) would work too.
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Roxanne Hicklin




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PostPosted: May 17, 2013 14:53    Post subject: Re: How to minimize Arsenic on Realgar  

Thanks Alfredo.
It's a relief to know it's not arsenic.
I think we'll just continue to wash the yellow powder off then and let him enjoy the specimen in the case with the rest of his minerals.

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Jordi Fabre
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PostPosted: May 17, 2013 14:57    Post subject: Re: How to minimize Arsenic on Realgar  

More info here: Realgar changes into Pararealgar or Orpiment?
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Mark Ost




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PostPosted: May 17, 2013 20:46    Post subject: Re: How to minimize Arsenic on Realgar  

Interestingly, especially for Jordi the term realgar comes by way of the Catalan language.
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Roxanne Hicklin




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PostPosted: May 18, 2013 06:28    Post subject: Re: How to minimize Arsenic on Realgar  

Thanks Jordi.
This is really great information. Maybe we will build a special box for it with special lighting to avoid the color specturm that's causing the problem. We have several separate niches in the collection. It would be just a matter of changing out the lighting, possibly.
Many thanks.
Roxanne

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Joaquin Montoro




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PostPosted: May 18, 2013 07:02    Post subject: Re: How to minimize Arsenic on Realgar  

Mark Ost wrote:
Interestingly, especially for Jordi the term realgar comes by way of the Catalan language.

Sorry, but the word Realgar comes from the arabic "Rahj-al-Ghar" what means "dust from the mine".

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lluis




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PostPosted: May 18, 2013 09:52    Post subject: Re: How to minimize Arsenic on Realgar  

Hi, Joaquin

Mark placed what is in wikipedia, that realgar comes from arabic rahj al-gar, powder of the mine, via catalan and medieval latin.
Then still via catalan

With best wishes

Lluís
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Roxanne Hicklin




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PostPosted: May 21, 2013 14:20    Post subject: Re: How to minimize Arsenic on Realgar  

I just want to verify that Pararealgar is non-toxic - right?
We assumed the yellow powder was arsenic, which is toxic.
But if it is pararealgar, I'm assuming it is harmless. Not that we will encourage people to ingest it, by any means.

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lluis




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PostPosted: May 21, 2013 14:35    Post subject: Re: How to minimize Arsenic on Realgar  

Roxanne

As far as I know, any arsenic component is toxic.
Even the arsenic compunds used long time ago to cure (or to try to cure) syphylis, were toxic
Pararealgar is toxic, as realgar is, besides.
https://cameo.mfa.org/browse/record.asp?subkey=12104
(link normalized by FMF)

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LLuís
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Roxanne Hicklin




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PostPosted: May 21, 2013 14:46    Post subject: Re: How to minimize Arsenic on Realgar  

Yes. I was afraid of that. :-)
Thanks for the clarification.
And thanks for all the advice and tips.
I may post a follow up to show everyone how we dealt with it, if we decide to build a suitable box for display.

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Tracy




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PostPosted: May 22, 2013 17:52    Post subject: Re: How to minimize Arsenic on Realgar  

ALL chemical substances are toxic, in high enough amounts! It is a question of exposure. I don't expect one to become poisoned by touching an arsenic specimen. Only, perhaps, by eating it, and even then not always...and while it may be argued that all arsenic substances are toxic, they are not all equally toxic. Organic arsenic is significantly less toxic than inorganic arsenic.

- Tracy

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Roger Warin




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PostPosted: May 23, 2013 02:08    Post subject: Re: How to minimize Arsenic on Realgar  

Hello Tracy,
What do you think when you talk about organic arsenic?
All heavy elements are toxic. But toxicity depends greatly on the solubility of the poison and therefore its ability to assimilation by the body.
Roger.
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lluis




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PostPosted: May 23, 2013 02:51    Post subject: Re: How to minimize Arsenic on Realgar  

Hy, Tracy

I agree with Roger

Yes, all compounds are toxic depending in quantities.
Common salt, used in cooking is poisonous if you eat, say, 500 gr. in one time.

If I do not remember it bad, arsenic was eaten normally in canton Vaud in Switzerland, because they say that it makes hair blacker and nails stronger....
I would not eat, it, by sure.

But it was used also as "succession powders" by Mme. LaVoisin in France in time of Louis XIV... The “succession”, well, you know what mean...

For organic arsenic compounds, well, Wikipedia says that are 500 times less toxic than inorganic species. But being in Wiki, searching a little, I found that cacodylcyanide is several times more poisonous than cyanhydric acid (used in gas cameras), and I would say that cacodyl itself is more poisonous than arsenic. Both are organic compounds...

https://trove.nla.gov.au/ndp/del/article/68707662
(link normalized by FMF)

In short: not to play with them....

With best wishes

Lluís
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Roger Warin




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PostPosted: May 23, 2013 07:04    Post subject: Re: How to minimize Arsenic on Realgar  

Hello,
This notion of poison may be off-topic, but it is still important to know the main dangers of a mineral collection: radioactive compounds (especially because of radon), liquid mercury, heavy elements ...
Since humans live on Earth, they are somehow acclimated to various "natural" poisons as long as they remain in low concentrations corresponding to the average quantities in the earth's crust.
In other words, the presence of arsenic as impurities (ppm) in orange juice does not seem toxic (for me). If this is what is called an organic arsenic, I agree with Tracy.
But be aware that there are organic derivatives of arsenic, which are highly toxic and dangerous, but never find in a collection. These are products of laboratories and industry.
It is the same for phosphorus element much like As, but lighter. Simple compounds are essential to life, while the organic P compounds are the basis of poisons and pesticides.
One can suck apatite (Ca-phosphate) lifetime without getting sick. The proof of tooth enamel is made of apatite (hydroxyl or fluorapatite). Hence the importance of fluorine for tooth enamel, but without excess of course.
Roger.
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Riccardo Modanesi




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PostPosted: May 23, 2013 07:12    Post subject: Re: How to minimize Arsenic on Realgar  

Hi to everybody! radioactive minerals, arsenic minerals, asbestos... even water itself is toxic if drunk in an excessive amount! All what I know is I have had asbestos, arsenic minerals (including bukovskite) and radioactive minerals in my collection for almost 40 years and I'm still alive and healthy. Otherwise an aphorism is valid: all kinds of chemical substances are edible (as well as all kinds of grasses and mushrooms!), but some of them just ONCE!!!! HAHAHAHAHA!!!
Greetings from Italy by Riccardo.

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