Abstract

Cathodoluminescence petrography was used to examine quartz grains contained in facies of the Upper Freeport coal bed (Middle Pennsylvanian) of west-central Pennsylvania. Samples included ash concentrates, polished blocks of different lithotypes, and standard petrographic pellets of specific gravity separates of facies channel samples. More than 80% of the quartz in mineral and vitrain-rich bands in the polished blocks of the Upper Freeport coal bed do not exhibit cathodoluminescence. In specific gravity separates of the coal, 100% of the quartz examined in the lightest gravity separates did not luminesce. In the heaviest gravity separates, which included shale-parting material, 60% of the quartz did not luminesce. In contrast, in a sample of shale directly overlying the coal bed, more than 90% of the quartz luminesced. On the basis of these cathodoluminescence data and other published data, quartz in the Upper Freeport coal bed is interpreted to be authigenic in origin. The authigenic quartz grains are postulated to have been derived from phytoclasts.

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