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 monohydride where the temperature is high enough. The reaction that produces it is either 2Mg + H → 2MgH or Mg + H → MgH. Decomposition is by the reverse process. Formation requires the presence of magnesium gas. The amount of magnesium gas is greatly reduced in cool stars by its extraction in clouds of enstatite, a magnesium silicate. Otherwise in these stars, below any magnesium silicate clouds where the temperature is hotter, the concentration of MgH is proportional to the square root of the pressure, and concentration of magnesium, and 10. MgH is the second most abundant magnesium containing gas