Magnetite
A black, strongly magnetic iron oxide found in some meteorites and in many Earth rocks that are mistaken for meteorites.
Magnetite is an iron oxide with the formula Fe₃O₄, and it is the most magnetic natural mineral. Pieces of it, called lodestone, can even act like magnets themselves. It is black, heavy and often shiny or metallic-looking.
In meteorites, magnetite tells a story about water and oxygen. In carbonaceous chondrites such as Orgueil, which fell in France in 1864, it forms tiny spheres, stacks of plates and clusters that grew when water flowed through the parent asteroid. Magnetite also forms in the fusion crust of many meteorites as they burn through the air. Tiny magnetite crystals in the Martian meteorite ALH 84001 became famous in 1996, when some scientists suggested they might have been made by microbes; most researchers now think non-biological processes can explain them.
Magnetite also causes many "meteorwrongs". Magnetite-rich Earth rocks and industrial slag stick to magnets just like real meteorites. A simple clue is the streak test: rubbing magnetite on unglazed white tile leaves a black streak. Real meteorites with metal usually show silvery flecks when a corner is ground, which only an adult should do with permission.
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Level: Explorer Ages 10 and up