Meridianiite is the mineral consisting of magnesium sulfate, MgSO 4·11H 2O. It is colorless transparent crystalline salt that precipitates from solutions saturated in Mg2+ and SO42− 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 , 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.