Black oxide of manganese , Manganese dioxide ∨ peroxide , ∨ Black manganese Meaning, Definition & Usage

Definitions
  1. (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.

Webster 1913