Copper Ps. After Aragonite with Chrysocolla, Corocoro, Pacajes Province, La Paz, Bolivia
This small thumbnail is a “floater” featuring several interpenetrating crystals, formerly aragonite, now replaced by copper, with secondary mineralization by turquoise-blue Chrysocolla, deep red cryptocrystalline cuprite, and white aragonite. The hexagonal habit of the replaced aragonite can be seen in several aspects shown. Due to differences in molecular volume between the parent and replacement molecules, the original hexagonal faces of the aragonite have been deformed to present a concave geometry. Insofar as I know, this is the only locality in the world that yielded copper specimens as a pseudomorph (replacement) after aragonite. The area of occurrence has been purchased by a Korean mining company for copper mining, which involves mass excavation, crushing and smelting. It is very unlikely that more specimens will be forthcoming unless mining operations cease. I used to come across these intriguing specimens many years ago, however, they have slowly disappeared from the marketplace. This piece is definitely an old-timer, as the typewritten label attests (complete with overstrike).
