An unusually large cluster of copper psuedomorphs after aragonite.  Typically these occur as single crystals around 1.5-2 cm in length, or as ball-shaped aggregates around the same size.

This piece is somewhat larger, and distinctly shows the numerous hexagonal pseudos that make it up.

The Corocoro copper deposit was abandoned in the mid 1980's, though was recently leased by a state-run South Korean firm, with plans to create an open pit and to process the tailings.  Unfortunately for us collectors, that means that these will probably only get harder to find with time.