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A Natural magnet
Magnetite(Fe3O4 mineral) is natural magnet. It is attracted to a common magnet.
Tiny crystals of magnetite are present in many rocks. In the crystallization of an igneous rock, tiny crystals of magnetite form in the melt, and because they are magnetic, they orient themselves with the direction and polarity of Earth's magnetic field. This preserves the orientation of the Earth's magnetic field within the rock at the moment of crystallization.