Meridianiite

Meridianiite is the mineral consisting of magnesium sulfate undecahydrate, MgSO4·11H2O. It is colorless transparent crystalline salt that precipitates from solutions saturated in Mg2+ and SO2−4 ions at temperatures less than 2 °C. The synthetic compound was formerly known as Fritzsche's salt. Meridianiite is a naturally occurring mineral species found on Earth in a variety of environments including sea ice, crusts and efflorescences in coal/metal mines, cave systems, oxidized zones of sulfide deposits, salt lakes/playas and Antarctic ice-cores. It is commonly associated with other evaporite minerals such as epsomite, mirabilite, halides, and other sodium-magnesium-sulfates. There is some evidence that it was once present on the surface of Mars, and may occur in several bodies of the Solar System. As of 2012, it was the only undecahydrate sulfate known.