Lithium is named from the Greek lithos, stone and was discovered in 1817. Lithium is the lightest of all metals with a density only about half that of water. It does not occur free in nature; combined it is found in small amounts in nearly all igneous rocks and in the waters of many mineral springs. Lepidolite, spodumene, petalite and amblygonite are the more important minerals containing it. Large deposits of spodumene are found in North Carolina. The metal has been used as an alloying agent and has nuclear applications. Lithium chloride is one of the most hygroscopic materials known, and it, as well as lithium bromide, is used in air conditioning and industrial drying systems. Lithium stearate is used as an all purpose and high temperature lubricant. Lithium is also used in dry cells and storage batteries.