Definify.com
Webster 1913 Edition
Pyrolusite
Pyrˊo-lu′site
,Noun.
[
Pyro-
+ Gr. [GREEK] to loose, or [GREEK] 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).