sedimentary

Chert (Siltstone-Chert mixture)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Dark brown to chocolate; Luster: Dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal to sub-conchoidal; Specific Gravity: 2.65

Hardness: 6
Color: Dark brown to chocolate
Luster: Dull to waxy

Identified June 12, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Dark brown to chocolate; Luster: Dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal to sub-conchoidal; Specific Gravity: 2.65

Formation & geological history

Formed from the accumulation of siliceous remains of marine organisms or chemical precipitation of silica in deep-sea environments. Often associated with ancient limestone or shale beds.

Uses & applications

Historically used for making stone tools (flintknapping) due to its sharp edges when broken. Currently used as road aggregate, in landscaping, and occasionally as lapidary material.

Geological facts

Chert is so hard it can create sparks when struck against steel. This specific brownish variety is sometimes colloquially called 'jasper' or 'flint' depending on the region.

Field identification & locations

Identify in the field by its hardness (it will scratch glass) and its smooth, shell-like (conchoidal) fracture pattern. Found globally in sedimentary basins.