Rutile is strongly coloured in plane light, in shades of yellow and brown, and has extreme positive relief, relative to clinopyroxene in A and plagioclase in C.  It is uniaxial and extinction is parallel to {110} cleavage and sections elongated parallel to the c axis.  Maximum interference colours are high-order white, but are typically masked by the yellow-brown absorption colour.  Grains commonly appear the same in plane polarized light and under crossed nicols (compare A and B). The orientation of the radiating acicular bundles in C and D appears to be, in part, crystallographically controlled by the host plagioclase grain.  A and B are  from an eclogite xenolith from the Moses Rock diatreme, Utah and C and D are in a granite from an unknown location.  All views are 2.2 mm across.  A and C ppl, B and D x-nicols.