Salt is the main mineral in the ocean, making up three-quarters of the 3.5 percent of dissolved minerals in seawater. Salt also occurs naturally in mineral deposits, and this is known as rock salt. Because New Zealand has no rock salt deposits, salt was imported from the time of European arrival in the early 1800s until the country developed a sea salt industry in the 1950s.
Today, much of our domestic salt comes from Lake Grassmere, a 15 square kilometre lake near Blenheim. Seawater, fresh from the Pacific Ocean, is pumped into Lake Grassmere. Warm winds blow across the exposed lake, evaporating water and increasing the concentration of salt. The very salty water is pumped into deep holding pens, then into shallow crystallisation ponds. As the water continues to evaporate, salt forms as a crust on the bottom of the ponds. The remaining water is pumped out and the dried salt is harvested, crushed, washed in brine and moved by giant conveyor belts to form huge mounds of white crystals which are visible from late summer.
Matt Ford from Dominion Salt says
