Halite is the natural crystalline form of sodium chloride, the compound commonly used as table salt.
It usually forms when salty water evaporates in restricted seas, salt lakes, or underground evaporite basins. Halite crystals belong to the cubic crystal system and commonly grow as cubes because of the arrangement of sodium and chloride ions.
Pure halite is colourless or white, but impurities can make it pink, blue, grey, or yellow. Thick ancient salt deposits may later flow slowly under pressure, forming domes and other structures known as salt tectonics.
Table salt is processed halite that may be refined, ground, and supplemented with iodine. Halite should not be confused with rock salt: rock salt is the geological material, often composed mostly of halite but potentially containing other evaporite minerals.