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What acid causes the tarnish on chalcopyrite resulting in the beautiful blue/green/purple coloration?

asked Aug 19, 2014 by aurorasrarfire (120 points)

1 Answer

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I think any strong acid will do it, but I think its commercially done with muriatic (hydrochloric) acid. I was once dissolving some stains off a prehnite with some minor chalcopyrite in a weak acid mix, and the chalcopyrite turned a beautiful iridescent blue.

answered Aug 21, 2014 by hershel (49,750 points)