Probably more than you think. Some scientists estimate that the oceans contain as much as 50 quadrillion tons (50 million billion tons) of dissolved solids. If the salt in the sea could be removed and spread evenly over Earth's land surface it would form a layer more than 500 feet thick (152.4 meters), about the height of a 40-story building. Seawater is 220 times saltier than fresh lake water. Unrefined sea salt contains 98.0% sodium chloride and up to 2.0% other minerals (salts). Together there are over 100 minerals, composed of 80 chemical elements, in sea salt. The composition of a single crystal of ocean salt is so complicated that no laboratory in the world can produce it from its basic 80 chemical elements.