mineral

Quartz River Cobble

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale). Color: Tan, yellowish-brown to white, often stained by iron oxides. Luster: Vitreous to waxy. Structure: Hexagonal/Trigonal (but rounded due to erosion). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Tan, yellowish-brown to white, often stained by iron oxides
Luster: Vitreous to waxy

Identified February 21, 2026More mineral →

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Physical properties

Formation & geological history

Formed through hydrothermal processes or within igneous rocks (like granite) and later liberated by weathering. This specific pebble was shaped by 'hydraulic rounding' in high-energy aqueous environments like rivers or beaches over thousands of years.

Uses & applications

Common river stones are used extensively in landscaping, drainage systems, and as concrete aggregate. High-purity quartz cobbles are used in glass manufacturing and silicon production.

Geological facts

Quartz is the most abundant mineral in the Earth's crust. Its high hardness allows it to survive long-distance transport in rivers, which is why it is the dominant component of most beach sands and river gravels.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife (7 hardness) and its translucent to opaque appearance. These are ubiquitous in riverbeds, glacial deposits, and sedimentary basins worldwide.