Rock salt is the mineral form of sodium chloride, otherwise known as table salt. You may also hear rock salt referred to as “halite,” especially when it is used industrially. This form of salt is available in most grocery stores, and also through hardware stores, which stock rock salt in massive bags for the purpose of keeping down ice on the roads in the winter. Salt lowers the freezing point of water, so rock salt has historically been used to salt icy roads in winter to melt the ice away.