igneous
Rhyolite
Rhyolite (felsic volcanic rock)
Hardness: 6-7 Mohs; Color: Light gray, tan, or pink; Luster: Dull or earthy; Texture: Fine-grained (aphanitic) or porphyritic; Cleavage: None; Specific Gravity: 2.4-2.6
- Hardness
- 6-7 Mohs
- Color
- Light gray, tan, or pink
- Luster
- Dull or earthy
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Physical properties
Hardness: 6-7 Mohs; Color: Light gray, tan, or pink; Luster: Dull or earthy; Texture: Fine-grained (aphanitic) or porphyritic; Cleavage: None; Specific Gravity: 2.4-2.6
Formation & geological history
Formed from rapid cooling of high-silica (felsic) magma at or near the Earth's surface. Usually associated with continental volcanic activity and can range from recent to hundreds of millions of years old.
Uses & applications
Used primarily as crushed stone for road construction, landscaping, and occasionally as a building stone or for making decorative aggregate.
Geological facts
Rhyolite has the same chemical composition as granite but cooled much faster. Famous for forming columns similar to basalt in some locations, and is the volcanic equivalent of granite.
Field identification & locations
Identify by its light color, fine texture, and inability to be scratched by a steel blade. Found in volcanic regions like the American West (e.g., Yellowstone) and the Andes mountain range.
