igneous
Rhyolite
Extrusive Felsic Igneous Rock
Hardness: 6 on the Mohs scale. Color: Pinkish, reddish, grey, or tan. Luster: Dull to vitreous on fresh crystal faces. Crystal structure: Aphanitic (fine-grained) to porphyritic, often with quartz and sanidine phenocrysts. Specific gravity: 2.35 to 2.55.
- Hardness
- 6 on the Mohs scale
- Color
- Pinkish, reddish, grey, or tan
- Luster
- Dull to vitreous on fresh crystal faces
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Physical properties
Hardness: 6 on the Mohs scale. Color: Pinkish, reddish, grey, or tan. Luster: Dull to vitreous on fresh crystal faces. Crystal structure: Aphanitic (fine-grained) to porphyritic, often with quartz and sanidine phenocrysts. Specific gravity: 2.35 to 2.55.
Formation & geological history
Formed from the rapid cooling of silica-rich lava extruded from volcanoes, typically associated with continental volcanic arcs and calderas.
Uses & applications
Used occasionally as decorative stone, in landscaping, and crushed for road construction materials.
Geological facts
Rhyolite is the extrusive equivalent of granite, meaning they share almost identical chemical compositions but cool at vastly different rates.
Field identification & locations
Identified by its fine-grained, often porphyritic texture in pink, tan, or grey tones. Common in volcanic regions worldwide.
