A rare example of wurtzite, cousin to the "other" more common zinc sulfide, sphalerite.  Although recent finds in Tanzania have reset the standard for the species, this remains an exceptional and exceedingly uncommon example from Peru.  I've seen pieces from neighboring Bolivia, but the couple I have seen from Peru have been generally poorly formed, or the wirtzite is just present as a sub-par accessory mineral.  On this piece, the several wirtzite rosettes are front and center, and the bright and nicely contrasting pyrite matrix certainly improves contrast and adds to the aesthetics of the piece.