sedimentary

Chert (Flint Nodules)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: typically tan, beige, or brown with a waxy luster; Cleavage: none, exhibits conchoidal fracture; Structure: microcrystalline quartz.

Hardness: 7 on Mohs scale
Color: typically tan, beige, or brown with a waxy luster

Identified July 11, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: typically tan, beige, or brown with a waxy luster; Cleavage: none, exhibits conchoidal fracture; Structure: microcrystalline quartz.

Formation & geological history

Formed through the accumulation of silica-rich organic debris (such as diatoms or radiolarians) or chemical precipitation within limestone or chalk beds during the Paleozoic to Cenozoic eras.

Uses & applications

Historically used for stone tools and fire-starting (flint); modernly used in road construction, landscaping, and occasionally as an abrasive or in ceramics.

Geological facts

Chert was one of the most important materials for early humans because its conchoidal fracture allows it to be chipped into sharp edges for knives and arrowheads.

Field identification & locations

Identify by its waxy appearance and extreme hardness (will scratch glass). Commonly found in stream beds or weathered out of limestone cliffs. Look for smooth, rounded surfaces and shard-like breaks.