Chert (often called Flint in various colors)

Physical Properties

Hardness: 7 (Mohs scale), Color: tan, grey, beige with waxy/dull luster, Crystal structure: Microcrystalline (hidden), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & Geological History

Formed through the accumulation of silica-rich organic remains or chemical precipitation within sedimentary rock layers, often occurring as nodules in limestone or chalk beds.

Uses & Applications

Historically used for stone tools (points, scrapers); currently used as a raw material for ceramics, construction aggregate, and occasionally for fire-starting.

Geological Facts

Chert possesses a conchoidal fracture which produces razor-sharp edges, making it the primary material for human tools for over a million years. It is extremely resistant to chemical weathering.

Field Identification & Locations

Identify in the field by its waxy texture, great hardness (scratches glass), and the way it breaks into curved, shell-like surfaces. Found globally in limestone formations.

Identified on: 4/17/2026

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