Magnesium sulfate constituents of evaporitic potassium-magnesium (K-Mg) salts deposits. Bright spots observed by the Dawn Spacecraft in Occator Crater on the dwarf planet Ceres are most consistent with reflected light from magnesium sulfate hexahydrate. Almost all known mineralogical forms of MgSO are hydrates. Epsomite is the natural analogue of "Epsom salt". Another heptahydrate, the copper-containing mineral alpersite (Mg,Cu)SO·7HO, was recently recognized. Both are, however, not the highest known hydrates of MgSO, due to the recent terrestrial find of meridianiite, MgSO·11HO, which is thought to also occur on Mars. Hexahydrite is the next lower (6) hydrate. Three next lower hydrates—pentahydrite, starkeyite, and especially
Magnesium oxychloride dioxide from the air to form magnesium chlorocarbonates. Anhydrous and partially hydrated forms also absorb water, turning into phase 5 and then phase 3 on the way to the chlorocarbonate. The exceptions are the dihydrate and hexahydrate of phase 9, that remain unchanged for many months. The crystal structure of phase 3 is triclinic with space group formula_1 and "z" = 2. The solid consists polymeric aquohydroxo cations, in the form of double chains of magnesium atoms surrounded and bridged by the oxygen atoms in hydroxy groups and complexed water molecules. These linear cations are interleaved and neutralized by chloride