MAGNETITE

ABOUT THE SPECIMEN As far as magnetite crystallization goes, this cabinet-size specimen checks all the boxes. All across the front are textbook octahedral crystals measuring to 1.7 cm, with classic gunmetal grey color and some reddish hues caused by oxidation. These specimens were extracted in the early 2000's, and they really don't turn up for sale all too often. Magnetite may not be a rare mineral, but specimens with this quality of display certainly are! The main display area is in excellent condition, the only detractions are around the edges and on the backside from where the piece was extracted.   VIDEO   MORE INFO The El Laco volcanic complex sits at 5,300 meters elevation in the Chilean Altiplano and hosts one of Earth's most unusual iron oxide-apatite deposits, formed approximately 2.0 Ma during Plio-Pleistocene volcanism. The magnetite occurs as lava flows, pyroclastic deposits, and subvolcanic dikes extruded from fissures on the volcano's flanks, representing the world's youngest and best-preserved Kiruna-type deposit. Specimens typically display octahedral crystals ranging from submillimeter to over 1 cm, often occurring as aggregates with metallic luster and rust-colored patina. What makes El Laco globally significant is its genesis through melt immiscibility; Fe-rich melts separated from andesitic magma and erupted as nearly pure magnetite lava. This process remains controversial, with ongoing debate between purely magmatic versus magmatic-hydrothermal models, though recent melt inclusion studies strongly support an igneous origin. Mining operations from the 1970s-1990s removed approximately 2 million tonnes, with the deposit designated an IUGS Geological Heritage Site in 2024. Collector specimens showing well-formed octahedra or spherules preserve evidence of this extraordinary volcanic iron mineralization process unmatched elsewhere on Earth.