sedimentary

Chert (Chert breccia)

SiO2 (Silicon Dioxide)

Hardness: 7 (Mohs scale), Color: tan, white, and brown. Luster: dull to waxy. Structure: microcrystalline quartz. Cleavage: none (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 (Mohs scale), Color: tan, white, and brown
Color: tan, white, and brown
Luster: dull to waxy

Identified July 8, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: tan, white, and brown. Luster: dull to waxy. Structure: microcrystalline quartz. Cleavage: none (conchoidal fracture). Specific Gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich fluids or biological remains (like radiolarians) in marine environments. This specific specimen shows brecciated or fragmented structures, likely from tectonic stress or collapse during deposition.

Uses & applications

Primarily used for decorative gravel, landscaping, and historically for stone tools (arrowheads). Small polished pieces are used for hobbyist collections and aquarium stones.

Geological facts

Chert and its variant flint were among the first resources used by early humans for tools because of their ability to break with very sharp edges. It is extremely chemically stable and resistant to weathering.

Field identification & locations

Look for a stone that is harder than steel (cannot be scratched by a knife) and exhibits a smooth, waxy surface with irregular, jagged patterns. Commonly found in riverbeds and limestone outcrops.