igneous
Porphyritic Andesite with Quartz
Andesite porphyry
AI-generated identification · may be incorrectHardness 6 on Mohs scale, grey groundmass with white plagioclase phenocrysts and a central vug filled with secondary quartz crystals. Vitreous luster on quartz, dull on groundmass.
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Physical properties
Hardness 6 on Mohs scale, grey groundmass with white plagioclase phenocrysts and a central vug filled with secondary quartz crystals. Vitreous luster on quartz, dull on groundmass.
Formation & geological history
Formed through two-stage cooling of intermediate volcanic magma, initially deep underground and later erupted at the surface.
Uses & applications
Used primarily in aggregate, construction, and road building. Collected as a geological teaching specimen.
Geological facts
Porphyritic texture indicates a complex cooling history where early-formed crystals floated in a liquid melt before final extrusion.
Field identification & locations
Identify by distinct white angular phenocrysts in a fine-grained grey matrix, often containing mineral-lined cavities. Found in volcanic arcs worldwide.
