igneous
Rhyolite
Rhyolite (High-silica volcanic rock)
Hardness: 6-7 on Mohs scale; Color: typically grayish-pink, reddish, or tan; Luster: dull to vitreous; Structure: aphanitic to porphyritic; Specific Gravity: 2.4-2.6
- Hardness
- 6-7 on Mohs scale
- Color
- typically grayish-pink, reddish, or tan
- Luster
- dull to vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: typically grayish-pink, reddish, or tan; Luster: dull to vitreous; Structure: aphanitic to porphyritic; Specific Gravity: 2.4-2.6
Formation & geological history
Formed from the rapid cooling of silica-rich (felsic) magma at the Earth's surface or at shallow depths. Often associated with continental volcanic arcs.
Uses & applications
Used primarily as road stone, aggregate in construction, and occasionally for decorative stone or arrowheads due to its conchoidal fracture.
Geological facts
Rhyolite is the volcanic equivalent of granite. Because of its high silica content, rhyolitic lava is extremely viscous and can erupt explosively, sometimes forming obsidian (volcanic glass) if cooled instantly.
Field identification & locations
Identify by its fine-grained texture and light color (felsic composition). Look for small crystals (phenocrysts) of quartz or feldspar embedded in the dense groundmass. Commonly found in mountainous volcanic regions.
