Mineral, KCl; sp. gr. 2.0; hardness 2; cubic; colourless to white, but sometimes shades of blue, yellow, or red; vitreous lustre; crystals usually cubes, often in combination with octahedra; cleavage perfect cubic; occurs in bedded evaporite deposits, but is one of the last minerals to precipitate because of its solubility in water; tastes much more bitter than halite. It is used extensively as a fertilizer.