A very nice example of chalcopyrite on pyrite, from Huanzala.  This mine is best known for the tons and tons of pyrite it produces, but it has also produced (or relatively rare occasions) good chalcopyrite.  This one isn't perfect (there is some damage) but it displays exactly as shown-- with the large brassy chalcopyrites aesthetically perched atop a cluster of ultra-lustrous pyrite crystals.