mineral

Quartz (River Pebble)

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale; Color: Grayish-white to tan/beige (translucent); Luster: Vitreous (glassy) to waxy when water-worn; Crystal structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on the Mohs scale
Color: Grayish-white to tan/beige (translucent)
Luster: Vitreous (glassy) to waxy when water-worn

Identified March 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the cooling of silica-rich magma or from hydrothermal veins. This specific specimen has been chemically and physically weathered and rounded by fluvial (river) action over thousands of years.

Uses & applications

Common river stones are used in landscaping, as aggregate in concrete, or for lapidary tumbling. High-purity quartz is used in electronics and glass manufacturing.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Specimens rounded by water are often called 'river pearls' or 'moonstones' colloquially in certain regions, though they are not true pearls or moonstones.

Field identification & locations

Identify in the field by its ability to scratch glass and its smooth, rounded surface indicating water transport. Commonly found in riverbeds, glacial deposits, and beaches. Collectors look for high translucency or interesting inclusions.