QAPF classification

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A modal classification scheme for igneous rocks with a colour index less than 90, based on the relative proportions of: quartz to quartz plus total feldspars (Q); alkali feldspar to total feldspars (A); plagioclase to total feldspars (P); and feldspathoids to feldspathoids plus total feldspar (F).

Subjects: Earth Sciences and Geography.

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