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Removing Tarnish From Pyrite
  
  Index -> Conserving, Preparing and Cleaning Minerals
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Casimir Sarisky




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PostPosted: Aug 21, 2015 14:46    Post subject: Removing Tarnish From Pyrite  

Hello,

I have recently acquired a miniature specimen of Pyrite on Hematite matrix from Elba Island, Italy. While I love its aesthetics and color, there is noticeable tarnish on a few of the crystal faces.

Since this is a small specimen and I know Pyrite is sensitive to water, how would I go about removing the tarnish without damaging the crystals? I want to be delicate as possible and try out the least messy/invasive methods if possible. Especially since I have never attempted such a thing before, and I am a major clutz.

You can some tarnish on the top of the large crystal in the attachment.



DSCN3371_zpsjheta9cf.JPG
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Rio Marina, Elba Island, Livorno Province, Tuscany, Italy
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 Viewed:  7141 Time(s)

DSCN3371_zpsjheta9cf.JPG


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kushmeja




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PostPosted: Aug 21, 2015 15:00    Post subject: Re: Removing Tarnish From Pyrite  

I'd try a dilute acid - like oxalic or muriatic acid. Just try with a dilute strength and for short intervals at first and you should be fine.

In my experience, I've cleaned similar pyrite specimens with hematite staining like yours has using muriatic acid at 1/3 strength, soaking for 30 mins up to 3-4 hours depending on how bad the staining was. Always err on the side of caution with acid though, so try a short 20-30 minute soak at first, followed by a thorough rinsing for a few minutes and a soak in water for double the time it was in the acid.
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GneissWare




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PostPosted: Aug 21, 2015 15:00    Post subject: Re: Removing Tarnish From Pyrite  

why do you want to remove it? Looks fine.
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Roger Warin




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PostPosted: Aug 21, 2015 15:56    Post subject: Re: Removing Tarnish From Pyrite  

Hi,
Beware of old names in chemistry.
Muriatic acid is actually HCl, an aqueous solution of hydrogen chloride gas. It is a highly corrosive, strong mineral acid.
It is not suitable to clean this face except at very high dilutions.
It should know the nature of the surface deposit before acting.
Roger.
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Casimir Sarisky




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PostPosted: Aug 21, 2015 16:11    Post subject: Re: Removing Tarnish From Pyrite  

I am not familiar with the chemicals mentioned so far (or with chemistry in general), or how they would react to the crystals themselves. I'd rather not experiment with such chemicals with my minerals. In that case I would use something that holds no value to me.

As I am not familiar with these chemicals, are there commercial/common household items that could be feasible without damaging the crystal faces?

Perhaps in use with a toothbrush? I would think the bristles of the brush would be too soft to cause any damage.


GneissWare wrote:
why do you want to remove it? Looks fine.


It is a bit more noticeable in person, and I am someone who is detail-oriented. I feel like if I can remove it safely, I need to do it.
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lluis




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PostPosted: Aug 22, 2015 02:26    Post subject: Re: Removing Tarnish From Pyrite  

Hi, Casimir, Gneissware, Roger

Casimir, I am also very maniac with details (ask Jordi for my tastes collecting... :-) ), but as Gneissware said, it looks fine to me.
And besides, as Roger commented, hydrochloric acid is very corrosive in materials that have iron, such as pyrite....It would take the rust out quickly, but if any trace of acid remains there, which is very easy.... you could get a "Museum of Horrors" sample of highly corroded pyrite, along with maybe more pieces damaged due to sulphide acid gasses released...

If you insist on trying to clean your specimen, I would try with a solution of mono phosphate of sodium. It should also clean the piece, but it is far less aggressive than hydrochloric acid. The use of a toothbrush should not damage the piece, unless the corrosion is too deep, and maybe you etch part of the surface....

All in all, the best is to do what Gneissware said. Let it be as it is....

I am a chemist, by the way.

With best wishes

Lluís
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alfredo
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PostPosted: Aug 22, 2015 22:59    Post subject: Re: Removing Tarnish From Pyrite  

I must disagree with those of you who say hydrochloric acid is too corrosive to clean pyrite. The biggest sellers of pyrite in the world by far are Peruvians, and they clean TONS of pyrite crystals every year with strong HCl before sending the crystals to market!
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lluis




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PostPosted: Aug 23, 2015 04:35    Post subject: Re: Removing Tarnish From Pyrite  

And many decay along the time....

Trouble is not cleaning, but time of of contact and even most important, cleaning all traces.....

Anyway, for tastes, are colors... So...

Personally, I do not use chlorhidric acid in my minerals and other things..... Except to etch benitoites from natrolite matrix.....

With best wishes

LLuís
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Casimir Sarisky




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PostPosted: Aug 24, 2015 00:46    Post subject: Re: Removing Tarnish From Pyrite  

Based on the conflicting opinions here, I will be cautious and will not attempt to remove the tarnish with any acidic solution. To be honest I thought it was preferable to remove all traces of tarnish from a specimen, but I am not going to risk damaging the specimen in the process.

One another forum I read a post stating that toothpaste and a toothbrush was effective in removing tarnish. Does anyone think this is valid?
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lluis




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PostPosted: Aug 24, 2015 05:44    Post subject: Re: Removing Tarnish From Pyrite  

Maybe

It would be an abrasive effect...
If abrasive in tooth paste is enough to remove tarnish, it will work. If not, well.....

With best wishes

Lluís
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GneissWare




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PostPosted: Aug 24, 2015 07:59    Post subject: Re: Removing Tarnish From Pyrite  

Casimir Sarisky wrote:
One another forum I read a post stating that toothpaste and a toothbrush was effective in removing tarnish. Does anyone think this is valid?

Depends on the abrasive used, but even a soft abrasive with enough scrubbing, will leave micro- to macro-scratches on the crystal surface. Toothpaste is good for teeth, but not most minerals.
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Casimir Sarisky




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PostPosted: Aug 24, 2015 14:39    Post subject: Re: Removing Tarnish From Pyrite  

GneissWare wrote:
Casimir Sarisky wrote:
One another forum I read a post stating that toothpaste and a toothbrush was effective in removing tarnish. Does anyone think this is valid?

Depends on the abrasive used, but even a soft abrasive with enough scrubbing, will leave micro- to macro-scratches on the crystal surface. Toothpaste is good for teeth, but not most minerals.


Then I am going to leave the tarnish alone then.

If I want to test removing tarnish with toothbrush/toothpaste, I will use a "leaverite" specimen.
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