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Some minerals show cleavage. That is, they break along flat surfaces called 'cleavage planes'. The only minerals that cleave are those whose atoms are 'arranged in a regular, repeating pattern'. These minerals form crystals which are an expression of that pattern.
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| For example................................... |
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The arrangement of atoms in calcite cause it to cleave in 2 directions forming crystals with a rhomboid shape. |
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Halite (salt) atoms are also arranged in a regular repeating pattern but in this case the pattern forms perfect cubes. | |
