Halite

Halite, the mineral form of sodium chloride (NaCl), is commonly known as rock salt. Pure halite is colorless and transparent, but most specimens are white or gray and may show pink, red, blue, or other colors due to impurities. Crystals are typically cubic, reflecting its isometric crystal system, and halite occurs as clear crystals, massive granular aggregates, or as beds within sedimentary evaporite sequences. It has a Mohs hardness of 2.5 and a density of about 2.16 g/cm3, and it is highly soluble in water.

Formation and occurrence are tied to the evaporation of saline waters in arid environments. Halite commonly forms thick beds in evaporite basins and can also crystallize from saline lakes and brines. In some regions, buoyant halite flows create diapirs that form salt domes. Associated evaporite minerals include gypsum, anhydrite, sylvite, and carnallite.

Halite is mined or recovered by solution mining in many parts of the world. In locations with abundant sunlight and warm climates, solar evaporation ponds concentrate brine to crystallize halite. The mineral’s principal use is as table salt for food, with large-scale industrial applications including chemical feedstock for chlorine and caustic soda production, de-icing of roads, and water treatment.

The name halite is derived from the Greek hals, meaning salt. Halite deposits are economically important and scientifically relevant for understanding evaporite processes and past climates.