schefflerite

schefflerite

[′shef·lə‚rīt]
(mineralogy)
(Ca,Mn)(Mg,Fe,Mn)-Si2O6 Brown to black variety of pyroxene that crystallizes in the monoclinic system and contains manganese and frequently iron.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.