sedimentary
Chert (often called Flint in archaeological contexts)
Microcrystalline or cryptocrystalline Silica (SiO2)
Hardness: 7 (Mohs scale); Color: gray, tan, or brown; Luster: waxy to dull; Cleavage: none (conchoidal fracture); Structure: cryptocrystalline.
- Hardness
- 7 (Mohs scale)
- Color
- gray, tan, or brown
- Luster
- waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: gray, tan, or brown; Luster: waxy to dull; Cleavage: none (conchoidal fracture); Structure: cryptocrystalline.
Formation & geological history
Formed as nodules or beds in sedimentary rocks through the precipitation of silica-rich fluids. This specific piece shows evidence of anthropogenic knapping (flake scars).
Uses & applications
Used historically by indigenous peoples for stone tools (arrowheads, scrapers) due to its sharp edges; used today as a decorative stone, in road base, and as a raw material for silicon.
Geological facts
Chert was one of the most important raw materials for early humans. This specimen is a 'flake' or 'debitage,' a byproduct of making a stone tool.
Field identification & locations
Identify in the field by its shell-like (conchoidal) fracture patterns, sharp edges, and hardness. Often found in limestone or chalk deposits.
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