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Techniques for CollectorsCleaning Chalcopyrite Crystals

1st Dec 2016 06:40 UTCPaul Stephen Cyr

I have run into some crystalline chalcopyrite specimens that often have a bit of crust. I have one crystalline piece soaking in Iron Out for now, which seems to be slowly "loosening" the hold of some black coating, but I am wanting to remove the coating in full. Would a calculated dip in muriatic acid be OK for what appears to be a sturdy crystal? It is attached to prehnite, so that is another concern- I could also clean manually with the dremel, but I would rather use chemical means if possible.

This thread is also for future information on cleaning chalcopyrite crystals and the mineral's chemical reactivity.

1st Dec 2016 12:32 UTCWayne Corwin

Paul

Are you using Iron Out or Super Iron Out ?

Sometimes it's not just a coating, but all the way thru.

Can we see a photo?

1st Dec 2016 16:45 UTCD. Peck

Paul, the chalcopyrite should be all right in HCl (although it would dissolve in HNO3). But the prehnite is soluble in HCl. I don't know how active the HCl is on the prehnite, but I would think it would certainly affect the luster at best and maybe dissolve points and edges.

1st Dec 2016 16:50 UTCReiner Mielke Expert

Test a piece first.You might end up with a pitted mess if some of the crust is an alteration product of the chalcopyrite.

1st Dec 2016 17:24 UTCPaul Stephen Cyr

Hey Wayne, thanks for your reply.

Using Super Iron out. After being in over night, the edges of the black crystalline area are looking clean, and are a bright blue with purple iridescence- I'm getting excited!

I'll take it out to dry before changing the solution today and get a pic for you.

By the way, the piece was collected in Paterson, New Jersey.

1st Dec 2016 17:39 UTCThomas Lühr Expert

Another suggestion: SIO will remove the crust, hopefully and depending on what it is. But the SIO generates also a multi-colored stain on the chalcopyrite.

A carefull treatment in a mixture of ammonia with some hydrogen peroxide should remove that staining and not affect the prehnite or calcite (if present).

Thomas

1st Dec 2016 18:57 UTCPaul Stephen Cyr

1st Dec 2016 18:59 UTCPaul Stephen Cyr

Thomas, I may keep it out and try your method. I have noticed a small crack in the chalcopyrite, but I figure a chemical treatment would be more gentle than abrasive methods. I figured abrasion would works as well, but would run the risk of interfering with the crystal structure.

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