White crystals of this very rare Na-Mg sulphate mineral vanthoffite from the famous Tolbachik volcano in Russia. Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Vanthoffite
Vanthoffite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Na₆Mg(SO₄)₄.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: Mohs hardness 3.5; specific gravity 2.694; Vitreous to pearly luster; optically biaxial.
IMA symbol Vhf, grandfathered status — known before the IMA’s founding, named in 1902.
Restricted to evaporite deposits of oceanic origin.
It is found associated with Löweite, langbeinite, halite (Berlepsch mine, Germany); blödite (Hall, Austria).
The mineral was named to honor Professor Jacobus Henricus van’t Hoff (1852–1911), German physical chemist, University of Berlin, Berlin, Germany.