Hematite after Magnetite

specimen number:
2062528

location:
Payun Matru Volcano, Agua Escondida, Malargue, Mendoza, Argentina

description:
Sharp octahedral crystals of what were once magnetite measuring to 3.0 cm in size, these now replaced by sparkling micaceous crystallized hematite, on a small amount of matrix. This is aesthetic and in great condition. The specimen comes with a previous label from the collection of Ray DeMark who acquired the specimen in 2002.

The Payun Matru Volcano, located in the Malargue Department of Mendoza, Argentina, is a large shield volcano featuring a summit caldera that formed through major activity between 168,000 and 82,000 years ago. Its geological history spans from the Plio-Pleistocene period to recent times, characterized by extensive basaltic and trachytic lava flows, including some of the longest Quaternary lava flows on Earth. While it does not have traditional opening and closing dates like a human-made structure, volcanic activity has occurred intermittently over hundreds of thousands of years, with the most recent minor eruptions taking place around 500 years ago, leaving the volcano currently dormant.

This region is particularly famous for producing exceptional mineral pseudomorphs known as martite, which consist of hematite completely replacing original magnetite crystals. During this alteration process, the mineral changes its internal composition while perfectly preserving the sharp, silvery-grey octahedral geometry and skeletal hopper crystal forms of the original magnetite. These specimens often display brilliant metallic lusters and open windows across their crystal faces, making them highly prized among mineral collectors for their striking sculptural appearance.

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