sedimentary

Chert Nodules (with Flint core)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: White exterior (cortex) with tan/grey interior; Luster: Waxy to dull; Structure: Cryptocrystalline; Conchoidal fracture.

Hardness: 7 Mohs
Color: White exterior (cortex) with tan/grey interior
Luster: Waxy to dull

Identified June 29, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: White exterior (cortex) with tan/grey interior; Luster: Waxy to dull; Structure: Cryptocrystalline; Conchoidal fracture.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) in seafloor sediments, eventually replacing carbonate material in limestone or chalk beds.

Uses & applications

Historically used for making stone tools (lithics) and starting fires; currently used for decorative stones, landscaping, and as a source of abrasive silica.

Geological facts

Flint and chert have been used for over 2 million years by early humans. This specimen shows a classic white 'cortex' which is a weathered outer layer of the silicious nodule.

Field identification & locations

Identified by its extremely smooth, waxy interior surface and its sharp, shell-like (conchoidal) breaking pattern. Found frequently in chalk outcrops or as river/beach pebbles.