mineral
Quartz Cobble (River Pebble)
Quartz (Silicon Dioxide - SiO2)
Hardness: 7 on Mohs scale; Color: Yellowish-tan to off-white; Luster: Glassy to greasy, smooth water-worn surface; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Yellowish-tan to off-white
- Luster
- Glassy to greasy, smooth water-worn surface
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellowish-tan to off-white; Luster: Glassy to greasy, smooth water-worn surface; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed initially in hydrothermal veins or igneous pegmatites, then eroded and rounded by long-term river and stream transport (fluvial erosion).
Uses & applications
Used for landscaping, decorative garden stones, rock tumbling, or as a general geological specimen. Pure quartz is utilized in electronics and glassmaking.
Geological facts
River-worn quartz pebbles are among the most resistant minerals to physical and chemical weathering, allowing them to survive thousands of years of transportation in riverbeds.
Field identification & locations
Identified by its high hardness (scratches glass, cannot be scratched by a steel nail), rounded river-worn texture, and lack of cleavage. Widely found in gravel bars, river beds, and alluvial deposits globally.
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