sedimentary

Chert (River Pebble)

Microcrystalline silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: greyish-green to tan; Luster: waxy to dull; Crystal Structure: Cryptocrystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: greyish-green to tan
Luster: waxy to dull

Identified June 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: greyish-green to tan; Luster: waxy to dull; Crystal Structure: Cryptocrystalline; 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 in marine or freshwater environments. This specimen has been rounded and smoothed by water transport (river action).

Uses & applications

Historically used for stone tools (arrowheads); currently used as road aggregate, architectural stone, or decorative landscaping pebbles.

Geological facts

Chert is so hard it can scratch steel and was once highly valued by indigenous peoples for its ability to produce a sharp edge when knapped.

Field identification & locations

Identify by its hardness (cannot be scratched by a knife), smooth texture, and curved 'conchoidal' fractures. Often found in riverbeds or coastal deposits.