The name chlorite applies to a group of minerals with a variety of compositions and optical characteristics.Chlorite occurs in many low to medium grade metamorphic rocks, and as an alteration product of other mafic silicates (e.g., biotite, pyroxene, hornblende). Chlorites typically have moderate positive relief relative to quartz and feldspars (views A and B). Most chlorites have pleochroism in shades of pale yellow and pale green (A and B), which is most pronounced in Fe-rich varieties.  Extinction is parallel or very slightly inclined.  Maximum interference colours range up to first order white, but are commonly anomalous in shades of brown, yellow, blue or purple.  The “stormy sky blue” interference colour in C is typical of Fe-rich chlorites, whereas the “khaki yellow-brown” of the chlorite in D is found in chlorites with intermediate values of Mg/(Mg+Fe).  A, B, and C are from the Skelly Creek pluton, Kootenay Lake, B.C. and D is from an uknown location. All views are 2.2 mm across.  A and B ppl, C and D x-nicols.