sedimentary

Chert (Jasper/Chalcedony variant)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: tan to reddish-brown, Luster: dull to waxy, Crystal Structure: Cryptocrystalline (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Hardness: 6

Identified June 27, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: tan to reddish-brown, Luster: dull to waxy, Crystal Structure: Cryptocrystalline (microscopic), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen likely originated as a silica-rich nodule within limestone or dolomite beds.

Uses & applications

Used historically for stone tools and weapons due to its sharp conchoidal fracture. Today used as abrasive material, decorative landscaping, and occasionally lapidary work.

Geological facts

Chert was one of the most important minerals for early humans, used to create arrowheads and scrapers. Because it is harder than steel, it can strike sparks against iron to start fires.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) breakage patterns. Commonly found in stream beds or eroded out of limestone cliffs.