A specimen from what has to be my favorite find of my last Peru trip-- tetrahedrite crystals on quartz.
The tetrahedrite is coated with tiny crystals of bournonite, and comes from a find made within the last several months. I saw a couple flats of this material in Tucson, but all were off matrix and had major damage issues. I saw one good lot of specimens while in Peru, this piece comes from that group.
Borth for the size and appearance of their surfaces, these crystals look a lot like the old tennantites from Tsumeb (of course, these are associated with quartz and those were not.)