Meridianiite — MgSO₄•11H₂O — is the crystalline 11-hydrate magnesium sulfate phase that precipitates from solutions saturated in Mg²⁺ and SO₄^2- ions at temperatures less than 2 °C. Clear to colorless, it is a naturally occurring mineral species found on Earth in a variety of environments including sea ice, crusts and efflorescence’s in coal/metal mines, cave systems, oxidized zones of sulfide deposits, salt lakes/playa’s and Antarctic ice-cores. Named for locality data obtained by the NASA Opportunity Rover at Meridiani Planum, it has been suggested that mineral casts present in the Martian sulfate deposits are indicative of this minerals former presence in the area. It is commonly associated with other evaporite minerals such as epsomite, mirabilite, halides, and other sodium-magnesium-sulfates.