magnēˈsia noun

1. An imagined substance sought by the alchemists (obsolete)
2. Manganese (obsolete)
3. A light white powder, oxide of magnesium
4. Basic magnesium carbonate, used as a medicine

magnēˈsian adjective

Belonging to, containing, or resembling magnesia

magnesite /magˈnəs-īt/ noun

Native magnesium carbonate

Magnesian Limestone noun

1. Dolomite rock
2. A division of the Permian of England