mineral

Quartz (River Pebble)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Milky white to light gray; Luster: Vitreous/waxy when polished; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Milky white to light gray
Luster: Vitreous/waxy when polished

Identified May 29, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Milky white to light gray; Luster: Vitreous/waxy when polished; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed from silica-rich hydrothermal veins or crystallizing from cooling magma. This specific specimen has been Rounded by water erosion in a fluvial (river) environment over thousands of years.

Uses & applications

Industrial uses include glassmaking, electronics (piezoelectric properties), and abrasives. Polished pebbles are used for garden landscaping, home decor, and aquarium gravel.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. When found in riverbeds, their smooth shape is the result of 'abrasion'—thousands of collisions with other rocks while being transported by water.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and lack of cleavage. Look for it along riverbanks, beaches, and glaciated areas. Common worldwide.