Sodalite is a rather uncommon mineral restricted to alkaline igneous rocks, and is commonly associated with other feldspathoids.  It is colourless to pale blue in plane light and is isotropic, with a low refractive index (n = 1.48-1.49), which gives it negative relief relative to nepheline or feldspars with which it commonly occurs. In these images, sodalite occupies much of the lower left corner, and has an albite inclusion.  The sodalite is pale blue in A, compared to the colourless plagioclase and the pale yellow cancrinite that occupies most of right side of these images.  Except for its blue colour, sodalite is easily confused with analcime.  Sample from a cancrinite-nepheline syenite from Bancroft, Ontario.  Images are 2.2 mm across. A ppl, B x-nicols.