n. [ F. manganèse, It. manganese, sasso magnesio; prob. corrupted from L. magnes, because of its resemblance to the magnet. See Magnet, and cf. Magnesia. ] (Chem.) An element obtained by reduction of its oxide, as a hard, grayish white metal, fusible with difficulty (melting point 1244° C), but easily oxidized. Its ores occur abundantly in nature as the minerals pyrolusite, manganite, etc. Symbol Mn. Atomic number 25; Atomic weight 54.938 [ C=12.011 ]. [ 1913 Webster +PJC ]

☞ An alloy of manganese with iron (called ferromanganese) is used to increase the density and hardness of steel. [ 1913 Webster ]

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. [ 1913 Webster ]

n. A brass alloy having from 1 to 4 percent of manganese added to harden it; made by adding manganese to the copper and zinc used in brass.
Syn. -- high-strength brass. [ WordNet 1.5 ]

. Cast steel containing a considerable percentage (10-14) of manganese, which makes it very hard and tough and highly resistant to wear. See Alloy steel, above. [ Webster 1913 Suppl. ]