sedimentary
Quartz Pebble
Silicon Dioxide (SiO2)
Hardness of 7 on the Mohs scale, typically brown, pinkish, or reddish-brown due to iron oxide staining, vitreous to waxy luster, trigonal crystal system when formed in vugs, conchoidal fracture with no cleavage, specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically brown, pinkish, or reddish-brown due to iron oxide staining, vitreous to waxy luster, trigonal crystal system when formed in vugs, conchoidal fracture with no cleavage, specific gravity of 2.65.
Formation & geological history
Formed through mechanical weathering and alluvial transport. Quartz is highly resistant to chemical and physical weathering, allowing it to survive long journeys in rivers, streams, and beaches, resulting in its smooth, rounded pebble shape.
Uses & applications
Used as landscape gravel, decorative stones, in construction aggregates, and as pocket specimens or lapidary practice for amateur rockhounds.
Geological facts
Quartz is one of the most abundant and durable minerals on Earth's continental crust. Smooth quartz pebbles found in rivers are often referred to as 'river stones' or 'stream-rounded quartz'.
Field identification & locations
Easily identified by its hardness (scratches glass), lack of cleavage, and smooth water-worn shape. Found worldwide in riverbeds, lake shores, beaches, and glacial deposits.
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