Crystal shape is different from cleavage, as we have seen. Quartz, which grows in lovely crystals, does not cleave at all. It fractures.
How do crystals form to begin with? Magma and lava, which is just magma on the surface of Earth, are just mixtures of different compounds and even sometimes elements such as gold. At different temperatures, different compounds begin to crystallize out of the magma (or lava). The slower the magma cools, the greater the time for crystals to grow. Eventually, all the magma will be crystallized, and the various crystals usually are mixed up with each other. The result of this mishmash of crystals is rocks! But some crystals will be NOT be mixed up with other kinds of crystals, and that's how minerals can form. Assignments:
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March 2020
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