mineral

Quartz (River Pebble)

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale; Color: Grayish-white to smoky translucent; Luster: Dull/Waxy (weathered) to Vitreous (fresh surface); Structure: Hexagonal crystal system (microcrystalline in this state); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on the Mohs scale
Color: Grayish-white to smoky translucent
Luster: Dull/Waxy (weathered) to Vitreous (fresh surface)

Identified March 27, 2026More mineral →

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Physical properties

Formation & geological history

Formed from silica-rich hydrothermal fluids or cooling magma. This specific specimen is a 'clast,' meaning it has been detached from its parent rock and weathered/rounded over thousands of years by water transport in a river or glacial environment.

Uses & applications

Used in glass manufacturing, electronics (piezoelectric properties), abrasives, and as a common component in concrete and construction aggregate.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Specimens rounded by water like this are often called 'river stones' or 'cobbles' and are frequently found in fluvial deposits globally.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife (it will scratch glass) and its lack of cleavage. Common in riverbeds, beaches, and gravel pits. Collectors often tumble these to reveal a gem-like interior.