The sodium-aluminum clinopyroxene jadeite forms in high-pressure, low-temperature environments, and is common in blueschist facies metamorphic rocks.  Jadeite has high relief and inclined extinction typical of pyroxenes.  In A, sprays of acicular jadeite stand out in positive relief relative to the aragonite vein in which they have grown.  Jadeite has maximum first order interference colours (B) that are anomalous in shades of blue and yellow due to dispersion of the optic axes.  Sample is of a jadeite-aragonite vein in glaucophane schist from Pacheco Pass, California.  Both views are 5.5 mm across. A ppl, B x-nicols.