Why this rock is probably not a meteorite:
1) It's too spherical. Meteorites are never this speherical because
there is no mechanism to make spherical rocks on asteroids or the
Moon. (We don't know yet whether any rocks on Mars are speherical.)
2) Up close the rock does appear to have a rind, and it's smoother
than where the rind is missing on top. However, the rind is too thick
to be a meteorite fusion crust, and
it really doesn't look glassy like a fusion crust. In meteorites,
the fusion crust is almost always darker than the inside of the meteorite.
The inside of this rock, where the rind is missing, is very dark.
3) The rock is dense, but not magnetic. It does not contain
metal. Up close, there are a few crystals of calcite exposed. Calcite
doesn't occur in meteorites. The bulk of the rock is so fine grained
that individual crystals cannot be seen with the naked eye. Meteorites
that do not contain metal will have visible mineral crystals or rock
fragments on the inside.
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What is it?
This strange looking, 42-pound object is called a coal ball. Coal
balls are not made of coal, but they are found only in coal beds.
Coal balls are ancient masses of peat that has been cemented by calcium
or magnesium carbonate. Coal balls are often rich in fossils.
This rock was found in a shop in Indiana. Coal balls are common in
coal deposits of Indiana and Illinois.
Here is a photo of the coal ball
pictured above along with another coal ball
that is in our department collection of rocks and minerals.
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