Rhyolite
“Granite's volcanic twin”
Igneous
Rhyolite is a fine-grained extrusive igneous rock with the same chemical composition as granite but formed at Earth's surface from rapidly cooling silica-rich lava. Its high silica content makes the magma extremely viscous, often leading to explosive eruptions.
Composition
quartz, feldspar, biotite, hornblende
Where Found
Yellowstone (USA), Iceland, New Zealand, Andes Mountains
Mohs Hardness
6-7
Fun Fact
The supervolcano beneath Yellowstone National Park sits atop an enormous chamber of rhyolitic magma capable of continent-scale eruptions.
Test Your Knowledge
What makes rhyolitic eruptions especially explosive compared to basaltic ones?
Related Specimens
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