Heat up a rock. Most likely, all you will get is a hot rock. But heat
up the right type of stone to just the right temperature and you could
end up with a magnet, scientists now report.
Long before people
invented the small magnets that stick to refrigerators or the big
magnets that pick up cars at the junkyard, people discovered natural
magnets. The most magnetic and common type is a lodestone. It consists
of a brownish-black mineral called magnetite. Lodestones are natural
compasses: Suspend one by a thread or wire and it will rotate until its
magnetic field is aligned with Earth’s magnetic field.
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