sedimentary

Chert (Flint / Jasper variant)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on the Mohs scale; Color: Grey, brown, dark green to yellowish-brown with irregular weathering patinas; Luster: Waxy to sub-vitreous; Fracture: Conchoidal; Structure: Microcrystalline/cryptocrystalline aggregate.

Hardness: 6
Luster: Waxy to sub-vitreous

Identified July 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine environment sediments through the accumulation of siliceous organism remains (like radiolarians or diatoms) or by chemical precipitation of silica in limestones and chalk beds.

Uses & applications

Historically used for stone tools, arrowheads, and spark-striking flintlocks due to sharp conchoidal fractures. Modern uses include landscaping, aggregate, and lapidary carving.

Geological facts

Chert was one of the most critical rock types for early humans. Its ability to fracture with extremely sharp edges made it the primary material for prehistoric tools and weaponry.

Field identification & locations

Identified by its high hardness (scratches glass readily), smooth waxy feel, and sharp conchoidal fracture edges. Found abundantly in stream beds, gravel deposits, and limestone outcrops globally.