a very soft, black, tetragonal mineral, MnO2, an ore of manganese used in making glass, paint, etc.; manganese dioxide
Webster’s New World College Dictionary, Fourth Edition, compiled by the
editors of Webster’s New World Dictionaries. Copyright © 2010 by Houghton
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Word origin of 'pyrolusite'
< Gr pyr
, a washing (< louein
, to wash < IE base *lou-
, to wash > lather
) + Ger -it
: used, when heated, to remove color from glass