igneous
Porphyritic Rhyolite
Porphyritic Rhyolite
AI-generated identification · may be incorrectHardness 6-7 on Mohs scale, grayish-purple matrix with distinct white feldspar phenocrysts, aphanitic to glassy luster, cryptocrystalline structure.
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Physical properties
Hardness 6-7 on Mohs scale, grayish-purple matrix with distinct white feldspar phenocrysts, aphanitic to glassy luster, cryptocrystalline structure.
Formation & geological history
Formed from rapid cooling of silica-rich magma near or at Earth's surface, trapping larger crystals within a fine-grained groundmass.
Uses & applications
Used locally as decorative gravel, in landscaping, and occasionally as dimension stone.
Geological facts
Porphyritic texture indicates a two-stage cooling history, starting slowly deep underground and finishing quickly upon eruption.
Field identification & locations
Identify by contrasting white mineral phenocrysts embedded in a dark purple or grey volcanic matrix; commonly found in ancient volcanic regions.
