sedimentary

Chert (Yellow Jasper/Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs); Color: Tan, yellow, ochre; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Tan, yellow, ochre
Luster: Waxy to dull

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Tan, yellow, ochre; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) or by chemical precipitation from silica-rich groundwater. Often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools and starting fires; currently used for decorative landscaping, gravel, jewelry (as jasper), and as flint for flintlock mechanisms.

Geological facts

Chert breaks with a conchoidal fracture, creating sharp edges that made it the primary material for arrowheads and spear points throughout human history.

Field identification & locations

Identify by its waxy texture, extreme hardness (scratches glass), and the way it breaks into curved, shell-like chips. Found globally in sedimentary basins.