Halite is the mineral name for common rock salt, chemically sodium-chloride (NaCl). In nature it usually occurs in amorphous to cryptocrystalline form. Larger, well-developed crystals are more of an exception and not stable unless preserved in zero moisture conditions. The crystals in this sample are of a variety known as hopper crystals, characterized by a stepped arrangement along the perimeters of perfectly square cubic crystals. Actual width is 110 mm.