Bassanite is a calcium sulfate mineral with formula CaSO4·0.5(H2O) or 2CaSO4·H2O. In other words it has half a water per CaSO4 unit hence its synonym hemihydrate. Bassanite was first described in 1910 for an occurrence on Mount Vesuvius. It was named for Italian paleontologist Francesco Bassani (1853-1916). At Vesuvius it occurs as alterations f...