mineral

Quartz Cobble (River Pebble)

Quartz (Silicon Dioxide - SiO2)

AI-generated identification · may be incorrect

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

Identified July 24, 2026More mineral →

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Physical properties

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.