The end members of the scapolite solid solution series, with feldspar-like compositions, are the sodic marialite and the calcic meionite.  Scapolite commonly occurs in place of feldspars in contact or regional metamorphic rocks, such as tactites (skarns) or marbles.  It is uniaxial and colourless in plane light, with two good {110} cleavages.  Refractive indices vary with composition, with Ca-rich varieties being  higher.   In A, it has negative relief relative to coexisting green clinopyroxene.  Interference colours range from low first order for sodic scapolite to upper second order for Ca-rich varieties.  The second order blue interference colour in B indicates a fairly calcic composition.  Extinction is parallel to {110} cleavage traces.  Sample is from a marble from the Grenville Province of eastern Ontario.  Views are 2.2 mm across.  A ppl, B x-nicols.