Extracting other mineral from salt in evaporated seawater
One material extracted from seawater is magnesium.

In the United States, magnesium is obtained principally with the Dow process, by electrolysis of fused magnesium chloride from brine and sea water [emphasis added]. A saline solution containing $\ce{Mg^{2+}}$ ions is first treated with lime (calcium oxide)[sic; calcium hydroxide would seem more likely] and the precipitated magnesium hydroxide is collected:


$\ce{Mg^{2+}(aq) + CaO(s) + H2O → Ca^{2+}(aq) + Mg(OH)2(s)}$


The hydroxide is then converted to a partial hydrate of magnesium chloride by treating the hydroxide with hydrochloric acid and heating of the product:


$\ce{Mg(OH)2(s) + 2 HCl → MgCl2(aq) + 2H2O(l)}$


The salt is then electrolyzed in the molten state. At the cathode, the Mg2+
 ion is reduced by two electrons to magnesium metal:


$\ce{Mg^{2+} + 2 e^− → Mg}$