sedimentary
Chert
Chert (SiO₂)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale); Color: Tan, brown, or gray with white inclusions; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6
- Hardness
- 7 (Mohs scale)
- Color
- Tan, brown, or gray with white inclusions
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, brown, or gray with white inclusions; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6
Formation & geological history
Formed in marine environments through the accumulation of silica-rich organic remains or chemical precipitation. This specimen appears water-worn, likely from a stream or river bed.
Uses & applications
Historically used for stone tools and starting fires; currently used in construction aggregate, road surfacing, and as decorative garden stones.
Geological facts
Chert is so hard it can scratch glass and steel. It was a primary material for prehistoric arrowheads and spear points due to its sharp edges when fractured.
Field identification & locations
Identify in the field by its waxy luster, smoothness, and conchoidal (shell-like) fracture patterns. Commonly found in limestone formations or as river pebbles.
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