sedimentary

Chert (Jasper/Flint variety)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Dark brown to tan/grey; Luster: Waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 7 Mohs scale
Color: Dark brown to tan/grey
Luster: Waxy to dull

Identified June 30, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Dark brown to tan/grey; 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 microfossils (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids, replacing original carbonate material in sedimentary beds.

Uses & applications

Historically used for stone tools (arrowheads). Currently used for lapidary work, jewelry (when colorful like Jasper), and as a durable construction aggregate.

Geological facts

Chert breaks with a conchoidal fracture, creating sharp edges which made it the primary material for prehistoric survival tools and weapons.

Field identification & locations

Identify by its extreme hardness (scratches glass), waxy feel, and smooth curved break surfaces. Commonly found as nodules in limestone or as layer-cake beds in maritime sedimentary sequences.