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, lustrous black, magnetic mineral, Fe3O4. It occurs in crystals of the cubic system, in masses, and as a loose sand. It is one of the important ores of iron (magnetic iron ore) and is a common constituent of igneous and metamorphic rocks.
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The naturally occurring magnetic iron oxide, or magnetite, possessing polarity, and attracting iron objects to itself. Also known as Hercules stone; leading stone; loadstone.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
a. a rock that consists of pure or nearly pure magnetite and thus is naturally magnetic
b. a piece of such rock, which can be used as a magnet and which was formerly used as a primitive compass
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005