mineral

Quartz (River Cobble)

Silicon Dioxide (SiO2)

Hardness: 7.0 Mohs; Color: Milky white to translucent grey; Luster: Vitreous to waxy; Crystal structure: Trigonal; No cleavage (conchoidal fracture); Specific gravity: 2.65

Hardness: 7
Color: Milky white to translucent grey
Luster: Vitreous to waxy

Identified June 25, 2026More mineral →

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Physical properties

Hardness: 7.0 Mohs; Color: Milky white to translucent grey; Luster: Vitreous to waxy; Crystal structure: Trigonal; No cleavage (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through hydrothermal processes or crystallization of molten rock. This specific specimen has been chemically and mechanically weathered into a smooth shape through aquatic transport in a river or beach environment.

Uses & applications

Used widely in glass making, ceramics, electronics (piezoelectric properties), and as decorative landscaping stone. Polished river stones are also significant in Feng Shui and aquarium decor.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. This specimen shows a 'frosting' effect common in river rocks due to numerous micro-impacts with other stones.

Field identification & locations

Identify by its hardness (it will easily scratch glass) and lack of cleavage. Found worldwide in riverbeds and mountainous terrain. A primary component of most sand.