sedimentary

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: tan, reddish-brown, grey; Luster: waxy to dull; Structure: microcrystalline/cryptocrystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 (Mohs scale), Color: tan, reddish-brown, grey
Color: tan, reddish-brown, grey
Luster: waxy to dull

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale), Color: tan, reddish-brown, grey; Luster: waxy to dull; Structure: microcrystalline/cryptocrystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed from the precipitation of silica-rich fluids or the accumulation of silica-based microorganisms (like radiolarians) in marine environments. Often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools/weapons due to its sharp edges. Modern uses include abrasive materials, road surfacing, and as a decorative stone/lapidary material if highly colorful.

Geological facts

Chert has been used by humans for millions of years to create arrowheads and scrapers. When struck against steel, it can produce sparks, leading to its historical use in flintlock firearms.

Field identification & locations

Identify in the field by its hardness (will scratch glass), smooth waxy feel, and conchoidal (shell-like) fracture patterns on broken surfaces. Often found in riverbeds or within sedimentary outcrops.