igneous
Rhyolite
Extrusive felsic igneous rock
Hardness: 6 on the Mohs scale. Color: Light shades of gray, tan, reddish-brown, or pink. Luster: Dull to earthy. Crystal structure: Aphanitic (fine-grained) to glassy, sometimes with phenocrysts (porphyritic texture). Specific gravity: 2.35 - 2.65.
- Hardness
- 6 on the Mohs scale
- Color
- Light shades of gray, tan, reddish-brown, or pink
- Luster
- Dull to earthy
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Physical properties
Hardness: 6 on the Mohs scale. Color: Light shades of gray, tan, reddish-brown, or pink. Luster: Dull to earthy. Crystal structure: Aphanitic (fine-grained) to glassy, sometimes with phenocrysts (porphyritic texture). Specific gravity: 2.35 - 2.65.
Formation & geological history
Formed from the rapid cooling of silica-rich lava on the Earth's surface or in shallow dome structures, typically associated with explosive continental volcanic eruptions.
Uses & applications
Used locally as crushed stone for construction, road aggregate, and sometimes in landscaping or as a decorative building stone.
Geological facts
Rhyolite is the extrusive equivalent of granite. Its high silica content makes its lava extremely viscous, often leading to violent volcanic eruptions rather than smooth lava flows.
Field identification & locations
Identify by its light overall color, fine-grained or porphyritic texture, and sometimes vesicular or flow-banded patterns. Commonly found in volcanic regions worldwide.
