mineral

Quartz (River Pebble)

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale; Color: Off-white/tan; Luster: Vitreous to dull (weathered); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on the Mohs scale
Color: Off-white/tan
Luster: Vitreous to dull (weathered)

Identified March 29, 2026More mineral →

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Physical properties

Hardness: 7 on the Mohs scale; Color: Off-white/tan; Luster: Vitreous to dull (weathered); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the crystallization of silica-rich magma or from hydrothermal veins. This specific specimen is a 'river pebble,' meaning it was eroded from parent rock and smoothed by water transport over centuries.

Uses & applications

Common industrial uses include glassmaking, abrasives, and electronics (as oscillators). Smooth pebbles like this are frequently used in landscaping, aquarium decor, and aggregate for concrete.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. It is chemically very stable, which is why it often survives the erosion process that dissolves other minerals, resulting in smooth river stones like this one.

Field identification & locations

Identify in the field by its hardness (it will scratch glass) and lack of visible grains or pores. Look for slightly translucent edges and a smooth, waxy feel when wet. Found globally in riverbeds, beaches, and glacial deposits.