\Pyr`o*lu"site\, n. [Pyro- + Gr. ? to loose, or ? a
loosing.] (Min.)
Manganese dioxide, a mineral of an iron-black or dark
steel-gray color and metallic luster, usually soft.
Pyrolusite parts with its oxygen at a red heat, and is
extensively used in discharging the brown and green tints of
glass (whence its name).