metamorphic
River Pebble / Quartzite Rock
Metamorphic Quartzite (primarily SiO2)
Hardness: 6.5-7 Mohs. Color: Grayish-brown, tan, and earthy tones. Luster: Dull to sub-vitreous. Crystal structure: Microcrystalline/granular. Cleavage: None. Specific Gravity: ~2.6-2.7.
- Hardness
- 6
- Color
- Grayish-brown, tan, and earthy tones
- Luster
- Dull to sub-vitreous
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Physical properties
Hardness: 6.5-7 Mohs. Color: Grayish-brown, tan, and earthy tones. Luster: Dull to sub-vitreous. Crystal structure: Microcrystalline/granular. Cleavage: None. Specific Gravity: ~2.6-2.7.
Formation & geological history
Formed from quartz-rich sandstone subjected to extreme heat and pressure during regional metamorphism, then weathered, rounded, and smoothed by river erosion over thousands of years.
Uses & applications
Used extensively in landscaping, river rock decor, aggregate for concrete, driveway gravel, and general construction.
Geological facts
River pebbles get their rounded, smooth shape through river abrasion, where water carries stones downstream, constantly colliding and grinding them against one another.
Field identification & locations
Identified by its hard, fine-grained texture, rounded edges, and inability to be scratched by a steel blade. Found along riverbeds, stream channels, beaches, and glacial gravel deposits globally.
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