mineral

Quartz (Riverstone / Cobble)

Silicon Dioxide (SiO2)

Hardness: 7 on the Mohs scale. Color: Translucent to opaque white/yellowish due to iron staining. Luster: Vitreous to waxy (when weathered). Crystal structure: Trigonal (often lost in rounded specimens). Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 on the Mohs scale
Color: Translucent to opaque white/yellowish due to iron staining
Luster: Vitreous to waxy (when weathered)

Identified March 7, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the cooling of magma or precipitation from hydrothermal veins. Often found as weather-resistant pebbles in riverbeds or alluvial deposits, where they have been rounded by water transport over thousands to millions of years.

Uses & applications

Commonly used in large quantities for landscaping, construction aggregate, and as a source of silica for glass manufacturing. Smooth, translucent pieces are often used as 'pocket stones' or for rock tumbling.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Because it is chemically stable and very hard, it survives transportation by water much longer than other minerals, which is why riverbeds are often filled with quartz pebbles like this one.

Field identification & locations

Identify in the field by its hardness (it will easily scratch glass) and its lack of cleavage planes. It is most commonly found in stream beds, beaches, and glacial till. Collectors look for pieces with high translucency or interesting inclusions.