sedimentary

Chert (often called Flint when dark or worked)

Cryptocrystalline silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Gray, tan, or brown with a waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 6
Color: Gray, tan, or brown with a waxy luster

Identified February 5, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Gray, tan, or brown with a waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation in marine environments. This specimen shows 'lithic reduction' or knapping, indicating it was shaped by humans.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) due to its sharp edges; industrially used for road metal and in the production of glass and ceramics.

Geological facts

This particular piece is a 'lithic artifact,' likely a preform or a scraper. Chert's conchoidal fracture allows it to break into razor-sharp edges, making it the most important material for prehistoric tool-making.

Field identification & locations

Identify in the field by its waxy texture and characteristic curved, shell-like fracture scars. Common in limestone deposits. Collectors of artifacts look for 'flakes' or 'bulb of percussion' marks which prove human manipulation.