sedimentary
Quartz Pebble
Crystalline Silica (SiO2)
Hardness: 7 on Mohs scale; Color: Brownish-gray, translucent to opaque; Luster: Dull to waxy when unpolished; Crystal Structure: Trigonal (often worn away in pebbles); Cleavage: None/Conchoidal fracture.
- Hardness
- 7 on Mohs scale
- Color
- Brownish-gray, translucent to opaque
- Luster
- Dull to waxy when unpolished
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Physical properties
Hardness: 7 on Mohs scale; Color: Brownish-gray, translucent to opaque; Luster: Dull to waxy when unpolished; Crystal Structure: Trigonal (often worn away in pebbles); Cleavage: None/Conchoidal fracture.
Formation & geological history
Formed via crystallization from silica-rich fluids or erosion of metamorphic/igneous veins. This specific specimen has been rounded by fluvial processes (water erosion) in a riverbed or coastal environment.
Uses & applications
Used as decorative landscaping stones, aquarium gravel, or crushed for industrial silica glass production.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. River-worn pebbles like this can travel hundreds of miles from their original source, becoming increasingly rounded over time.
Field identification & locations
Identify by its inability to be scratched by a steel knife and its lack of visible grains (unlike sandstone). Commonly found in riverbeds, beaches, and glacial till.
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