sedimentary
Chert (Flint)
Cryptocrystalline Silica (SiO2)
Hardness: 7 Mohs, Color: Tan/White, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6
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Physical properties
Hardness: 7 Mohs, Color: Tan/White, Luster: Waxy to dull, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6
Formation & geological history
Formed primarily by the accumulation of siliceous remains of microscopic organisms like diatoms or radiolarians, or through chemical precipitation in marine environments. Common in limestone and chalk beds.
Uses & applications
Historically used for stone tools and starting fires; currently used as a raw material in ceramics, abrasives, and as decorative stone in landscaping.
Geological facts
Flint was used by early humans for over 2 million years to create sharp-edged tools due to its predictable conchoidal fracture patterns.
Field identification & locations
Identified in the field by its hardness (scratches glass), waxy appearance, and sharp, shell-like edges when broken. Frequently found in stream beds or weathered out of limestone.
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