A member of the clinopyroxenes with a very low calcium content and the composition (Ca,Mg,Fe(Mg,Fe)Si2O6; sp. gr. 3.30–3.46; hardness 6.0; properties similar to augite, but occurs in rapidly chilled igneous rocks. In slowly cooled rocks, pigeonite changes to an orthopyroxene as cooling proceeds.
Subjects: Earth Sciences and Geography.