sedimentary

Chert (Jasper variation)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Brownish-red with white quartz veining; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Brownish-red with white quartz veining
Luster: Waxy to dull

Identified April 1, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Brownish-red with white quartz veining; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed from the accumulation of silica-rich microfossils like radiolaria or diatoms on the ocean floor, subsequently compacted and hardened. It can also form through chemical precipitation from silica-rich fluids.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to its sharp edges. Modernly used for landscaping, tumbled stones, and semi-precious jewelry (as Jasper).

Geological facts

Chert is so hard it can scratch steel. When struck against steel, it can produce sparks, leading to its historical use in flintlock firearms.

Field identification & locations

Identify by its smooth, waxy surface and shell-like (conchoidal) fractures. Often found in riverbeds or as nodules within limestone or chalk formations.