sedimentary

Chert (Flint nodule fragment)

Microcrystalline / Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray to brownish-gray interior with a chalky white weathering cortex; Luster: Waxy to dull; Fracture: Distinct conchoidal fracture; Specific gravity: ~2.65.

Hardness: 7 on Mohs scale
Luster: Waxy to dull

Identified November 15, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray to brownish-gray interior with a chalky white weathering cortex; Luster: Waxy to dull; Fracture: Distinct conchoidal fracture; Specific gravity: ~2.65.

Formation & geological history

Formed biogenically or diagenetically by the accumulation of siliceous microscopic organisms (such as radiolarians or sponge spicules) within carbonate muds or limestones/chalks, typically during marine deposition.

Uses & applications

Historically used for knapping prehistoric stone tools, weapons, and fire-starting (flint strikers). Currently used as aggregate, decorative landscaping stone, and architectural flint facing.

Geological facts

Flint and chert have played a crucial role in human technological evolution, being the primary material of the Stone Age due to their predictable conchoidal fracturing and ability to hold razor-sharp edges.

Field identification & locations

Easily identified by its high hardness (scratches glass easily), smooth or waxy texture on broken faces, conchoidal fracture, and often a soft, chalky white outer rind (cortex) when found weathered out of limestone or chalk beds.