sedimentary

Chert (Flint nodule)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: White weathered exterior (cortex) with a gray/black waxy interior; Luster: its waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Luster: its waxy to vitreous

Identified April 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic debris (like sponge spicules or radiolarians) or chemical precipitation in sedimentary environments like limestone or chalk. Often found as nodules within host rock.

Uses & applications

Historically used for stone tools and weapons. Currently used as road aggregate, in glass manufacturing, and as 'flint' in fire-starting kits.

Geological facts

Chert breaks with a conchoidal fracture, creating extremely sharp edges. It was the primary material for arrowheads and scrapers during the Stone Age. The white outer layer is called a 'cortex,' caused by chemical weathering.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its waxy internal texture when broken, and its characteristic curved, shell-like fracture pattern. Often found in riverbeds or eroding out of limestone cliffs.