Crystalline Structure
A crystalline structure is an ordered, repeated way in which atoms are arranged. This allows a mineral to grow in specific patterns. Crystal structure is the reason minerals will show specific physical properties such as cleavage (how minerals break) and symmetry, making them easier to be identified. Although minerals may differ in other ways, there are only 7 crystal families that a mineral can form: isometric, tetragonal, orthorhombic, monoclinic, triclinic, hexagonal, and trigonal.
Some minerals are considered polymorphs, which means they may have the same chemical composition as another mineral, but form in a completely different way. A good example of this is carbon and diamonds. Both of these minerals are made from carbon, but they form in very different ways. Graphite, the “lead” used in pencils, is very soft and breaks easily, whereas diamonds are the hardest natural mineral. This is a result of the carbon atoms bonding or connecting to each other in different ways.
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