Definify.com
Webster 1913 Edition
Manganesate
Manˊga-ne′sate
,Noun.
 (Chem.) 
A manganate. 
[Obs.] 
☞ An alloy of manganese with iron (called ferromanganese) is used to increase the density and hardness of steel. 
Black oxide of manganese
, Manganese dioxide 
or Manganese peroxide
, or 
Black manganese 
(Chem.)
, a heavy black powder 
 MnO2
, occurring native as the mineral pyrolusite, and valuable as a strong oxidizer; – called also familiarly manganese
. It colors glass violet, and is used as a decolorizer to remove the green tint of impure glass.