sedimentary

Chert (Flint/Jasper)

Silicon dioxide (SiO2) - Microcrystalline quartz

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brown to grayish-black; Luster: Vitreous to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 6
Color: Brown to grayish-black
Luster: Vitreous to waxy

Identified June 14, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown to grayish-black; Luster: Vitreous to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed as nodules or layers in sedimentary rocks (like limestone) through the accumulation of silica-rich organic remains or chemical precipitation from groundwater. Age varies from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) and fire-starting (flint). Used today in ceramics, road construction, and as aquarium or landscaping gravel.

Geological facts

Because it breaks with a conchoidal fracture, it creates sharp edges that are harder than steel. It was the primary material for the 'Stone Age' technological revolution.

Field identification & locations

Identify by its waxy appearance, extreme hardness (can scratch glass), and the way it flakes into shell-like curved surfaces. Often found in chalk or limestone deposits.