igneous
Porphyritic Andesite
Andesite porphyry
AI-generated identification · may be incorrectMohs hardness 6-7; grey to dark brown color with distinct lighter plagioclase feldspar phenocrysts; subvitreous to dull luster; aphanitic to fine-grained groundmass.
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Physical properties
Mohs hardness 6-7; grey to dark brown color with distinct lighter plagioclase feldspar phenocrysts; subvitreous to dull luster; aphanitic to fine-grained groundmass.
Formation & geological history
Formed from intermediate volcanic magmas that cooled in two stages, initially deep underground and then erupting to the surface.
Uses & applications
Used in construction, as aggregate for road building, and occasionally as decorative dimensional stone.
Geological facts
Andesite gets its name from the Andes Mountain range where it is exceptionally abundant along subduction zones.
Field identification & locations
Identify by the prominent contrasting phenocrysts embedded in a fine-grained dark volcanic matrix. Common in volcanic regions worldwide.
