sedimentary

Quartz Pebble (Chalcedony / Chert Pebble)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

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

Identified July 27, 2026More sedimentary →

Explore Quartz Pebble (Chalcedony / Chert Pebble) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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.