A rare example of tennantite from the Julcani Mine, operated since 1907.  This piece comes from more recent workings, and consists of tennantite crystals with a very thin coating of pyrite.  Although both tetrahedrite and tennantite are known to occur at this mine, tennantite is known to form the more complex crystals seen here (as opposed to simple tetrahedrons) , though more precisely work done on the pyrite-coated specimens in particular has shown these to be an tennantite-leaning intermediate in the tennantite-tetrahedrite series.

 Specifics aside, it’s a beautiful specimen and a very unusual example of Peruvian sulfide material—I can’t actually recall having seen others for sale.  It’s certainly different from the more typical tetrahedrite plates  that the country is known for.