sedimentary
Chert (often called Flint in archaeological contexts)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, white, and translucent; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, white, and translucent
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, white, and translucent; Luster: Waxy to dull; Crystal Structure: Cryptocrystalline (microscopic quartz); 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 chemical precipitation from groundwater within carbonate host rocks like limestone. It can form as nodules or bedded layers.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) and starting fires. Modern use includes road surfacing, grinding media, and as a semi-precious gemstone when colorful.
Geological facts
Chert breaks with a conchoidal (shell-like) fracture, creating razor-sharp edges. This property made it the primary material for tool-making during the Stone Age.
Field identification & locations
Identify in the field by its waxy texture and the way it chips away in curved, shallow bowls. It will easily scratch glass and generate sparks when struck against steel.
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