What is Vanthoffite?
Vanthoffite is a sodium magnesium sulfate evaporite associated with highly saline deposits and valued for its unusual sulfate chemistry.
Mineralogy and structure
Reference formula: Na6Mg(SO4)4. Vanthoffite is monoclinic; COD 9007484 is an exact structural reference. Its water-soluble sulfate chemistry makes humidity control more important than surface polish. Vanthoffite is classified with sulfates and has monoclinic crystal symmetry. Typical hardness is 3–3.5 on the Mohs scale and specific gravity is approximately 2.7–2.8.
Colour, lustre and habit
Typical colours include colourless, white, grey, yellowish. The usual prismatic, granular, massive habit and vitreous, pearly lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Vanthoffite forms in or is associated with evaporite basins, saline lakes, salt deposits and highly concentrated sulfate brines. Important documented localities include Germany, Russia, Canada, the United States and other evaporite districts.
Saline evaporite chemistry in a pale crystal
Vanthoffite gives a mineral collection a direct record of evaporation and brine evolution. Freshness, dryness and a documented salt deposit make it more compelling than a generic white aggregate.
Collecting and care
Keep dry and sealed, avoid washing and prolonged humidity, and protect soft crystals from abrasion.
