sodium chloride does, and so can be
separated. The sodium chloride in turn
crystallizes before the magnesium salts,
whose slight residue on the crystal surfaces
can then be washed off in new brine.
Crystal Shapes These days both edible rock
salt and sea salts are produced from brines by
evaporating the water away. The evaporation
process determines the kinds of salt crystals
produced. If the brine becomes concentrated
rapidly in a closed tank and crystallization
takes place throughout the brine, then many
small, regular cubic crystals are formed: the
familiar granulated salt of the salt shaker.
However, if the evaporation proceeds slowly
and at least partly in an open container or sea-
side pool, so that crystallization occurs
primarily at the brine surface, then the salt
solidifies into fragile, hollow, pyramid-shaped
flakes, a useful shape for sticking to the
surfaces of baked goods, and for dissolving