sedimentary

Chert (Green variety)

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: Pale green to olive, Luster: Waxy to dull, Crystal structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Identified June 4, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: Pale green to olive, Luster: Waxy to dull, Crystal structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation in marine environments. Often found as nodules or bedded deposits in limestone or shale.

Uses & applications

Historically used for stone tools due to sharp edges; currently used for road construction, landscaping, and semi-precious lapidary work.

Geological facts

Chert is so hard it can scratch steel and produce sparks when struck against iron; it has been used by humans for hundreds of thousands of years to create arrowheads and scrapers.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its ability to scratch glass. Commonly found in sedimentary basins and riverbeds as rounded pebbles.