Minerals are naturally occurring elements or compounds that are normally crystalline and that have been formed as a result of geological processes. They are the building blocks that make up rocks and are often used in the production of ceramics. Minerals have a characteristic chemical composition and a highly ordered atomic structure, which can be readily identified by several physical properties such as hardness, lustre, streak, and cleavage. There are over 5800 different minerals, each classified by both its chemical composition and crystal structure. Some minerals are only made up of one element, such as metals, gemstones, simple ores, and the only liquid metal mineral, mercury. Minerals are essential for good health, and the body needs minerals such as calcium, phosphorus, potassium, sodium, chloride, magnesium, iron, zinc, iodine, chromium, copper, fluoride, molybdenum, manganese, and selenium to develop and function normally.