Halite. Credit: Mineral Information Institute.
Large crystals of halite.
Halite, also known as rock salt, is naturally occurring sodium chloride (common salt, NaCl) crystallizing in the cubic (isometric) system. It is colorless or white (sometimes blue) when pure but may be colored pink, red, gray, or brown by the presence of impurities. It is found in evaporite sedimentary rocks, often found in association with gypsum and anhydrite, in salt domes and dried lakes. Halite was named by E. F. Glocker in 1847 after the Greek hals, meaning 'salt'. Hardness 2.5; relative density 2.2.