sedimentary

Chert (Jasper/Chalcedony Pebble)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Tan, brown, or grayish; Luster: Waxy to dull; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 Mohs scale
Color: Tan, brown, or grayish
Luster: Waxy to dull

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Tan, brown, or grayish; Luster: Waxy to dull; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation from groundwater within sedimentary beds. This specific specimen appears to be a water-worn river pebble.

Uses & applications

Used historically for stone tools due to sharp edges; currently used as aggregate, decorative landscaping, and occasionally for tumbling as pocket stones.

Geological facts

Chert and its varieties like jasper were the primary materials for arrowheads and scrapers in prehistoric times. It is resistant to chemical weathering and often survives long after the host rock has eroded.

Field identification & locations

Commonly found in riverbeds, glacial tills, and limestone outcrops globally. Look for a smooth, waxy texture and broad, shell-like (conchoidal) breaks on edges.