Hornblende is a common pleochroic mineral in many igneous and metamorphic rocks.  In A, B and C it stands out relative to enclosing plagioclase by the high relief and dark colours relative to the plagioclase. The two orientations in A and B, viewed down the c axis and rotated 90 degrees  relative to one another, illustrate the pleochroic colours of this brown variety, as well as the prominent and diagnostic amphibole {110} cleavages intersecting at approximately 56 and 124 degrees.  Hornblende has inclined extinction, and the grain in D illustrates that it is not extinct when the trace of the {110} cleavage is parallel to the cross hairs.  The maximum interference colours (and pleochroic schemes) of members of the amphibole group, including hornblende, are compositionally dependent and vary considerably, but the mid-second order interference colours in D are typical of many varieties of hornblende.   The sample is a garnet-clinopyroxene amphibolite from Parry Sound, Ontario.  All views are 2.2 mm across.  A, B,C ppl, D x-nicols.