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 rapidly. To be preserved, the flakes must be scooped off the surface before they settle and sink into the brine, where they fill in and become the large, coarse crystal often seen in minimally processed sea salts.