alba: (literally "white magnesia") was a hydrated magnesium carbonate, also known as mild magnesian earth. [ Black, Scheele] 4MgCO3.Mg(OH)2.5H2O was magnesia alba levis, and MgCO3.Mg(OH)2.4H2O was magnesia alba ponderosa. ... nigra: (literally "black magnesia") was the mineral pyrolusite, natural manganese dioxide, MnO2, sometimes also called simply magnesia or manganese. [ Scheele] Eventually manganese became the name of the metal present in the mineral.