In the late 90’s I ran across some faceted Pyrite stones. I thought they looked neat and wanted a few for my collection so I got 14 stones at auction. Received the stones and thought they looked great. Bagged and boxed them and added them to my collection.
Haven’t looked at them since then.
Pulled them out today and they have tarnished and turned almost black with age. I would like to clean these up but can’t use any acid cleaners on them and not sure If soap and water will do the trick.
Would like your ideas on how to clean these up without doing damage to the surface.
THANKS.
Hi there,
On pyrite you cán use acid, no problem at all… doing it all the time myself and it is fast. The results are always amazing!
You can either use hydrochloric acid or phosforic acid, both diluted, but not necessarily heavily diluted. In a plastic or glass container of course…
Make sure you are wearing rubber gloves and safety glasses.
Leave the stones in for 24 hours, rinse and admire your new stones again!
Have fun 
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Oh… btw… do not use nitric acid, that one wíll dissolve the stones…
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all sulfides oxidize in air and moisture… I’ve picked up some nice pyrite samples off of mine dumps and all of them have slowly disintegrated in humid air… old mine dumps themselves are significant sources of ground water and stream pollution… sulfides oxidize creating sulfuric acid which will leach out arsenic, cadmium and other toxic heavy metals… cleaning oxidized pyrite should be done gently with acids…organic reducing acids like citric acid, oxalic acid will slowly clean oxidized sulfides not only by acid cleaning but also by reducing ferric iron which is black (hematite and magnetite) into ferrous iron that is water soluble… stay away from oxidizing acids!.. Nitric acid is a very powerful oxidant and will burn up virtually everything that is oxidable…preventing oxidation is more important that letting pyrite blacken and having to clean it up over and over again until there’s nothing left… using a light oil such as sewing machine oil, or even a light wax to seal out oxygen once cleaned will help keep it from blackening… this is the same problem that jewelers face in keeping their tools at a high polish and rust free…
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