Clinopyroxene is common in plutonic gabbros, pyroxenites and peridotites, as a phenocryst in mafic to intermediate volcanic rocks, and in various medium to high grade metamorphic rocks.  Calcic clinopyroxenes such as diopside and augite are typically colourless (A and C) to pale brown or pale green in plane light, and some Fe-rich varieties may be weakly pleochroic.  Relief is high (positive) relative to quartz and feldspars (e.g., compared to plagioclase in A).  Clinopyroxenes have two good {110} cleavages that intersect near 90 degrees (A and C).  Interference colours range to upper second order (B and D).  Extinction is inclined to traces of the {100} cleavage (i.e., in cases where the c axis is near horizontal), and sections cut perpendicular to the c axis yield lower first order colours (B and D).  A and B are from a troctolite from an unknown location and C and D are from a Hawaiian basalt.  All views are 5.5 mm across.  A and C ppl, B and D x-nicols.