sedimentary

Chert (Flint/Chalcedony)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Gray/Bluish-gray with brown inclusions, Luster: Waxy to vitreous, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65

Identified May 10, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: Gray/Bluish-gray with brown inclusions, Luster: Waxy to vitreous, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in marine limestone formations where it replaces carbonate minerals over millions of years.

Uses & applications

Historically used for stone tools and fire-starting. Currently used in road construction, as an abrasive, and occasionally in jewelry as tumble-polished stones.

Geological facts

Chert is so hard it can scratch glass and steel. It was the primary material for spearheads and arrowheads for thousands of years due to its shell-like (conchoidal) fracture which creates razor-sharp edges.

Field identification & locations

Identify in the field by its waxy texture, smoothness despite weathering, and razor-sharp edges when broken. Frequently found in riverbeds or eroded limestone outcrops.