sedimentary

Chert (Jasper / Quartz pebble)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: reddish-brown, tan, and creamy beige. Luster: dull to waxy. Fracture: conchoidal. Microcrystalline structure with smooth, rounded surfaces from weathering.

Hardness: 6
Color: reddish-brown, tan, and creamy beige
Luster: dull to waxy

Identified July 26, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: reddish-brown, tan, and creamy beige. Luster: dull to waxy. Fracture: conchoidal. Microcrystalline structure with smooth, rounded surfaces from weathering.

Formation & geological history

Formed through the accumulation of silica-rich microfossils or precipitation from silica-rich fluids in sedimentary environments. Highly resistant to chemical weathering, causing it to persist as river and beach pebbles.

Uses & applications

Historically used for making stone tools, arrowheads, and spark-striking flints. Today used primarily in aggregate, landscape gravel, lapidary tumbling, and casual rock collecting.

Geological facts

Chert has been used by humans for hundreds of thousands of years to create sharp-edged tools. When struck against iron or steel, chert can produce sparks, which made it crucial for early fire-starting and flintlock firearms.

Field identification & locations

Identified by its high hardness (scratches glass), smooth waxy feel, and conchoidal fracture. Extremely common in riverbeds, gravel pits, beaches, and sedimentary rock formations worldwide.