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vivianite and light
  
  Index -> Conserving, Preparing and Cleaning Minerals
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Deborah Deitsch-Perez




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PostPosted: Dec 26, 2019 15:18    Post subject: vivianite and light  

We bought the vivianite shown in figure 18. Thinking of including it in the MAD case at Tucson. Is that a bad idea? I have seen some articles about vivianite reacting to light. It has been kept in a case in a room that has little natural light and is dark unless we are showing the cases. We have had it about 5 years and we have seen no change in the coloration.


vivianite IMG_4135 (002).jpg
 Mineral: Vivianite
 Locality:
Amazonas, Mato Grosso, Brazil
 Description:
Vivianite with ludlamite
 Viewed:  9292 Time(s)

vivianite IMG_4135 (002).jpg


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Jordi Fabre
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PostPosted: Dec 26, 2019 15:42    Post subject: Re: vivianite and light  

Deborah Deitsch-Perez wrote:
...Is that a bad idea?...


Yes

Deborah Deitsch-Perez wrote:
...We have had it about 5 years and we have seen no change in the coloration..


You live in a very dry place and far of the sea, and you protected the specimen of the light. Although Tucson is also dry, the change of conditions, the condensation inside the case, other mineral species all around and of course the powerful light could damage it.
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alfredo
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PostPosted: Dec 27, 2019 04:30    Post subject: Re: vivianite and light  

Several years ago I wrote an article about this topic. I hope you might find it helpful:

https://www.mindat.org/article.php/137/A+Scientific+Study+of+the+Absorption+of+Evil+by+Vivianite
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Roger Warin




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PostPosted: Dec 27, 2019 16:38    Post subject: Re: vivianite and light  

Hi Alfredo,
I really enjoyed reading your article.
Do you allow me to reproduce it in my little AGAB-Minibul review? http://www.agab.be
(In French language).
Best regards,
Roger.
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Deborah Deitsch-Perez




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PostPosted: Dec 27, 2019 16:39    Post subject: Re: vivianite and light  

Thanks, great article!
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alfredo
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PostPosted: Dec 27, 2019 17:03    Post subject: Re: vivianite and light  

No problem, Roger. You‘re welcome to reproduce it.
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bob kerr




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PostPosted: Dec 27, 2019 22:09    Post subject: Re: vivianite and light  

a very enjoyable article - thanks, Alfredo.

i have purchased a number of wonderful vivianites - mainly from Bolivia and many/most were associated with pyrite. to my dismay, they all "flaked or sheaved" apart and then simply fell apart. the slices leftover were still gemmy and green but the specimen simply fell apart.

after much discussion with people i think should and do know, the culprit was the moisture in the air (I live in very humid western PA) interacting with the pyrite or other sulfides in the matrix and forming sulfuric acid which then took out the specimen.

I guess mine didn't see the light of day long enough to experience the photo effects presented by Alfredo. so, from my perspective - in addition to Alfredo's "keep in the dark" solution, I would add the keep dry solution also.

the bottom line to me is that vivianite simply do not reside in my collection and never will - once burned, twice learned.

bob
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Roger Warin




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PostPosted: Dec 27, 2019 23:49    Post subject: Re: vivianite and light  

Hello Alfredo,
Thank you so much for your help in a problem I had never tackled. Most often think of iron sulfides. So, I am wondering about pyrrhotite. It is a terrestrial mineral that is never found in meteorites. In the reducing medium that is space, we only have the perfectly balanced FeS troilite. Troilite hardly exists on Earth. Pyrrhotite only exists on Earth, like pyrite. Sulfur chemistry is particular with its possibility of forming covalent bonds in sulfide anions like (S-S) 2-.
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alfredo
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PostPosted: Dec 28, 2019 03:46    Post subject: Re: vivianite and light  

"the bottom line to me is that vivianite simply do not reside in my collection and never will - once burned, twice learned."

Bob, That‘s why Rock Currier used to say that fine vivianites were not for the investment conscious.

I think vivianites are also heat sensitive. I had some stored for several years in dark flats in an attic under a roof in New York. No air conditioning, and it got very hot under the roof in summer. All the vivianites were destroyed, with or without pyrite.

I do not believe that vivianite itself is sensitive to humidity. They come after all from mines that are very humid inside. But you may well be right that the associated pyrites are sensitive to humidity. Pyrite confuses me... Why does it remain intact inside a wet mine but then decompose when you take it home? Some other factor at work?
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