Rhyolite   This crystal-rich rhyolite contains phenocrysts of quartz, K-feldspar (sanidine), plagioclase, and biotite in a fine-grained groundmass. Note the interesting shape of the (partially resorbed? skeletal?) quartz grain in the center of the photograph.		UNC sample R-15 ("rhyolite" card"
		Rock type rhyolite
		Locality unknown