sedimentary

Chert Nodules / Flint

Crystalline Silica (SiO2)

Hardness: 7 Mohs scale. Color: White, tan, or gray exterior with a waxy luster. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.65.

Hardness: 7 Mohs scale
Color: White, tan, or gray exterior with a waxy luster

Identified June 13, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale. Color: White, tan, or gray exterior with a waxy luster. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.65.

Formation & geological history

Formed by the accumulation of siliceous remains of organisms or chemical precipitation within limestone or chalk beds. Commonly found in Mesozoic or Cenozoic sedimentary layers.

Uses & applications

Historically used for stone tools and starting fires (striking steel). Modernly used in construction aggregate and as a collector's curiosity.

Geological facts

Flint was the primary material for prehistoric survival tools due to its sharp conchoidal edges. Chert nodules often resemble small, smooth eggs or potatoes when weathered out of their host rock.

Field identification & locations

Identify in the field by its high hardness (scratches glass), waxy look when broken, and presence as nodules within softer carbonate rocks like limestone. Common in riverbeds and coastlines.