Diamonds are classified as minerals. Diamonds are a form of native carbons and are formed in the Earth's mantle, which is the layer below the crust.
Diamonds are ranked as a 10 on Mohs scale of mineral hardness, making diamonds the hardest minerals. Due to their hardness, diamonds are commonly used in edge cutting and grinding tools.
Diamonds used in jewelry are cut to various shapes and sizes. Popular cuts include the princess cut, which is a square shape, round, cushion, emerald and oval. The cut, color, clarity and carat are the characteristics that determine the value of a diamond.