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The
dinosaur sculpture seen at the south entrance to Columbia 150
(1979) by Steve Gillman, is made of slabs of polished basalt from
a local quarry. Notice the difference in grain size between the
granite wall we just observed and the slabs of basalt. The size
of the crystals in rocks depends on the cooling rate. When magma
cools slowly, large crystals can form, when it cools quickly only
smaller crystals have time to form.
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