Rostite
Rostite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Al(SO₄)(OH)·5H₂O.
It crystallizes in the orthorhombic crystal system (space group Pcab). It is a member of the Khademite structural group.
Key properties: specific gravity 1.892; optically biaxial.
IMA symbol Rst, IMA status: approved, named in 1979.
Found in burning waste heaps at a coal mine, formed by decomposition of aluminum-bearing rocks by gasses containing SO2 and fluorine (Libušı́n, Czech Republic).
It is found associated with Tschermigite, alunogen, copiapite (Libušı́n, Czech Republic).
The mineral was named to honor Professor Rudolph Rost (1902–?), Czech mineralogist, Charles University, Prague, Czech Republic, who first characterized the mineral.