Sea salt crystals. Coloured scanning electron micrograph (SEM) of crystals of sea salt (a form of the mineral sodium chloride, NaCl). Sea salt is a coarse (large-grained) type formed naturally by the evaporation of sea water. Unlike other types of salt, it contains traces of elements like zinc, magnesium, iron, calcium, potassium, manganese and iodine. This gives sea salts a distinctive taste. The size of the crystals can be changed by grinding to obtain fine-grained varieties from the coarse varieties. Magnification: x115 when printed 10cm wide.