Type of volcanic rock containing large porphyritic crystals of quartz
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Quartz porphyry from the island of Alnö, Sweden. Phenocrysts of clear glassy rounded quartz and white orthoclase feldspar are set in a fine-grained matrix. Sample is just over 10 cm long
Quartz-porphyry, in layman's terms, is a type of volcanic (igneous) rock containing large porphyritic crystals of quartz.[1][2] These rocks are classified as hemi-crystalline acid rocks.
