Group of doubly terminated crystals of pseudomorphic hematite after magnetite, elongated and with defined faces and edges. They show exceptional skeletal growths, very marked and partially coated by recrystallizations of small crystals of lenticular hematite. The crystals were formed in the fumaroles of this enormous Argentinian volcano. The Payún Matrú is a large volcano with an intermediate morphological type between a volcanic shield and a stratovolcano, that is located 530 km from the oceanic fosa and marks the subduction zone of the Nazca plate. Currently this area is a national park and collecting minerals is prohibited.