sedimentary
Quartz Pebble (Chalcedony / Chert Pebble)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Yellowish-brown, tan, and translucent grey; Luster: Waxy to vitreous; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Yellowish-brown, tan, and translucent grey
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellowish-brown, tan, and translucent grey; Luster: Waxy to vitreous; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the deposition of silica-rich fluids in sedimentary or volcanic rock cavities, followed by weathering and stream or river transport that rounded the pebble over time.
Uses & applications
Commonly used in landscaping, tumbling for rock hounding collections, aggregate in construction, and occasionally for lapidary carving.
Geological facts
Stream-rounded quartz and chert pebbles are among the most durable rocks on Earth's surface due to their high hardness and chemical resistance to weathering.
Field identification & locations
Look for a smooth, rounded water-worn surface with conchoidal fractures and translucency around the edges when backlit. Frequently found along riverbeds, beaches, and gravel pits.
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