sedimentary

Chert

Chert (Microcrystalline Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Brown, grey, tan with oxidation; Luster: Dull to waxy; Texture: Fine-grained/cryptocrystalline; Cleavage: None (conchoidal fracture)

Hardness: 7 Mohs scale
Color: Brown, grey, tan with oxidation
Luster: Dull to waxy

Identified July 2, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Brown, grey, tan with oxidation; Luster: Dull to waxy; Texture: Fine-grained/cryptocrystalline; Cleavage: None (conchoidal fracture)

Formation & geological history

Chemically precipitated from silica-rich fluids or through the accumulation of siliceous remains of microorganisms (like diatoms or radiolarians) within sedimentary layers. This weathered pebble-form suggests transport by water.

Uses & applications

Historically used for stone tools (arrowheads/knives) due to sharp edges; currently used for landscaping, road base, and as a collector's specimen for nature enthusiasts.

Geological facts

Chert is essentially the same as flint, though the name 'flint' is usually reserved for dark varieties found in chalk formations. It is very resistant to physical and chemical weathering.

Field identification & locations

Identify by its extreme hardness (will scratch glass) and smooth, curved (conchoidal) fracture surfaces. Commonly found in riverbeds, glacial till, and coastal deposits.