igneous
Rhyolite
Rhyolite
Hardness: 6-7 on Mohs scale; Color: Pink, reddish-brown, or gray; Luster: Dull to sub-vitreous; Structure: Aphanitic (fine-grained) often with flow banding; Specific Gravity: 2.4-2.6
- Hardness
- 6-7 on Mohs scale
- Color
- Pink, reddish-brown, or gray
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Pink, reddish-brown, or gray; Luster: Dull to sub-vitreous; Structure: Aphanitic (fine-grained) often with flow banding; Specific Gravity: 2.4-2.6
Formation & geological history
Formed through the rapid cooling of silica-rich (felsic) magma on or near the Earth's surface during volcanic eruptions. It is the extrusive equivalent of granite.
Uses & applications
Used as crushed stone for road construction, fill material, and occasionally as structural stone or in landscaping. Decorative varieties with flow banding are used for lapidary work.
Geological facts
Rhyolite has the same chemical composition as granite but cooled much faster. High silica content makes rhyolitic lava very viscous, often leading to explosive eruptions.
Field identification & locations
Identify by its light color (pink/tan/grey), fine-grained texture, and characteristic 'flow bands' or wavy lines. Found in volcanic regions like the American West (Rocky Mountains).
