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diopside An important pyroxene CaMgSi2O6, and member of the clinopyroxenes, forming a continuous series with hedenbergite CaFeSi2O6; this series may be called diopside solid solution series and denoted diss (or Diss); sp. gr. 3.22 (di) to 3.44 (hed); hardness 5.5–6.0; monoclinic; normally a pale, dirty green or grey (or, rarely, colourless); vitreous lustre; crystals usually short, prismatic, columnar grains, but the bulk are irregular grains; cleavage prismatic good {110}; a common constituent of magmatic, basic, and ultrabasic rocks, e.g. pyroxenites, peridotites, gabbros, and diabases, and also occurs in basalts and dolerites; it is common in many metamorphic rocks, particularly metamorphosed dolomites and calcareous sediments. Chrome diopside is a bright green, chromium-rich (1–2% Cr2O3) variety commonly found in kimberlite pipes.