igneous
Rhyolite
Rhyolite, felsic extrusive igneous rock
Hardness 6-7, typically light-colored (pink, gray, or brown), dull to glassy luster, porphyritic texture with phenocrysts (often quartz or feldspar) in a fine-grained groundmass.
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Physical properties
Hardness 6-7, typically light-colored (pink, gray, or brown), dull to glassy luster, porphyritic texture with phenocrysts (often quartz or feldspar) in a fine-grained groundmass.
Formation & geological history
Forms from the rapid cooling of highly viscous, silica-rich lava at or near the Earth's surface. Can be of various geological ages.
Uses & applications
Crushed stone for construction, aggregate, sometimes as an ornamental stone.
Geological facts
Rhyolite has a similar mineral composition to granite but is extrusive (fine-grained) rather than intrusive (coarse-grained).
Field identification & locations
Identify by its light color and fine-grained texture often with small visible crystals. Commonly found in areas of past or present explosive volcanic activity.
