A relationship between cathodoluminescence color and metamorphic grade is shown by two sequences of naturally deformed quartzites. The metamorphic grade of quartzites from the Bergell Alps varies from low greenschist to high amphibolite. The metamorphic grade of quartzites from the Johnson Spring Formation of Inyo County, California is not precisely known, but the degree of metamorphism varies from slight alteration to complete recrystallization. Luminescence of detrital grains in undeformed quartzite is heterogeneous and varies from dull red to blue. Secondary quartz overgrowths and veins luminesce a rusty red color. Greenschist-facies samples also luminesce rusty red. Recrystallized and amphibolite-facies samples luminesce blue violet. Of the quartzites examined, those from near contacts with granite in the Bergell Alps had the bluest quartz cathodoluminescence. Metamorphism appears to homogenize luminescence with the color being related to metamorphic grade—low temperature causing red luminescence and high temperature, blue.

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