Cleavage vs. Crystal Shape
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Cleavage vs. Crystal Shape
It can be hard to decide what's a cleavage surface, and what's a crystal face. Crystal shape has to do with the way a mineral will "grow" if it has enough room. (If it is crowded, the crystal shape might be clear only under a microscope, not in a hand specimen). Cleavage, on the other hand, refers to the way a mineral breaks - if you whack it with a hammer, does it break into cubes? Does it always break so that it's like a sheet of paper? That's cleavage. Some minerals don't really have cleavage, they don't always break a certain way. But others, for example, pyrite, break alone certain preferred planes. A cube of pyrite, if you whack it with a hammer, with break into - little cubes of pyrite. That's cleavage, in the case of a cube, it's cleavage in three directions.
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| Jennifer Mathes, Ph.D. |
