Sodium chloride; NaCl + various rocks and minerals; Molar mass for NaCl only 58.443 g/mol. Also known as halite, rock salt, brown rock salt, grit salt. Halite varies considerably in its composition and colour depending on where it was deposited in the world. This sample from a mine in Cheshire is crushed sodium chloride crystals mixed with sand, blown in from deserts when it was being deposited in vast salt lakes. They date from the Triassic period, more than 220 million years ago. Today its main use is as gritting salt for clearing roads of ice and snow. Higher quality rock salts, the Himalayan rock salt, for instance, have become trendy condiments. lt for clearing roads of ice and snow. Higher quality rock salts, the Himalayan rock salt, for instance, have become boutique salt condiments.