Rhyolite
Rock made of quartz, sanidine, plagioclase
Common
The most silica-rich of the volcanic rocks, light-coloured, fine-grained or glassy, the lava equivalent of granite. Its thick magma tends to explode rather than flow, so it erupts more often as tuff, pumice and obsidian than as lava.
Rock
- Kind of rock
- Volcanic igneous rock
- Rock family
- Volcanic rock
- Texture
- fine-grained (crystals too small to see), glassy, porphyritic (large crystals in a fine groundmass)
- Also contains
- Mica, Hornblende
- Deposits
- Volcanogenic massive sulfide deposit
- How it forms
- Silica-rich magma extruded from a vent cools quickly at the surface, usually in explosive eruptions.
- Uses
- Quarried for weapons and tools in prehistoric eastern North America; its tuffs for building, its pumice as an abrasive.
Crystallography
- Habits
- Massive
Physical properties
- Luster
- Dull, Vitreous
- Colors
- white, pale gray, pink
- Transparency
- Opaque
Geology
- Origins
- Volcanic
- Geography
- worldwide, Iceland, Chile (Chaitén, Cordón Caulle), USA (Pennsylvania, Massachusetts)
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- Rhyolite. Wikipedia.
- M. R. Gillespie, M. T. Styles, BGS Rock Classification Scheme, Volume 1: Classification of igneous rocks (Research Report RR 99-06). British Geological Survey, 1999.
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