sedimentary

Banded Chert Pebble

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Light grey to off-white with dark grey micro-crystalline silica bands; Luster: Dull to waxy; Cleavage: None (conchoidal fracture); Specific Gravity: ~2.65

Hardness: 6
Luster: Dull to waxy

Identified July 24, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Light grey to off-white with dark grey micro-crystalline silica bands; Luster: Dull to waxy; Cleavage: None (conchoidal fracture); Specific Gravity: ~2.65

Formation & geological history

Formed by the precipitation of microcrystalline silica or accumulation of siliceous organisms in marine or lacustrine sedimentary environments. Weathered and rounded into a pebble by stream or ocean wave action.

Uses & applications

Used historically for tool-making; currently collected as pocket stones, landscape rock, or decorative polished pebbles.

Geological facts

Chert was essential to early human history because its conchoidal fracture creates extremely sharp edges suitable for arrowheads, scrapers, and blades.

Field identification & locations

Identified by its smoothness, hardness (scratches glass), dull-to-waxy luster, and smooth, rounded water-worn shape. Frequently found along riverbeds and ocean beaches.