A bischofite is a saline evaporite, consisting of magnesium chloride with the chemical formula MgCl2·6H2O, found with potash deposits in Saxony.
The common name for magnesium chloride is "bitter salt" or "magnesium salt."
If you mean MgCl2 , it' a salts are typical ionic halides, being highly soluble in water. The hydrated magnesium chloride can be extracted from brine or sea water. Magnesium chloride as the natural mineral Bischofite is also extracted (solution mining) out of ancient seabeds, for example the Zechstein seabed in NW Europe. Anhydrous magnesium chloride is the principal precursor to magnesium metal, which is produced on a large scale. Natural occurrence of anhydrous form was not confirmed. thx!