Clinopyroxenes rich in the acmite end member occur in alkaline igneous rocks and some blueschist and eclogite facies metamorphic rocks. Those with modest acmite component are referred to as aegirine-augite.  Acmite is strongly coloured and pleochroic in shades of green, yellow and brown (A, B).  It has high positive relief relative to quartz and feldspar (and coexisting sodalite in A).  The good {110} cleavage typical of pyroxenes is evident in A and B.  Interference colours range to third order (C), although this section may be a little thick.  Extinction is slightly inclined (0-20 degrees).  In D, granular aegirine-augite occurs in a feldspar matrix.  It is strongly coloured and pleochroic (indicated by different colours of different crystals), and some show colour zoning with lighter cores indicating lower acmite component.  A, B and C from naugite (sodalite cumulate) from Greenland and D from pyroxene syenite from Batbjerg Complex, Kangerdlugssuaq, East Greenland.  Views A-C are 5.5 mm across and D is 2.2 mm across.  A, B and D ppl, C x-nicols.