sedimentary
Chert (specifically Flint or Common Chert)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Gray, tan, blue-gray; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (hexagonal system); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Gray, tan, blue-gray
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Gray, tan, blue-gray; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (hexagonal system); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation and recrystallization of microscopic silica-rich organic remains (like radiolaria or diatoms) or by chemical precipitation within limestone/chalk beds. Associated with various geological ages from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) and fire-starting (flint and steel). Currently used as aggregate in road construction and occasionally as an ornamental gemstone.
Geological facts
Chert was one of the most important materials for early humans due to its ability to produce razor-sharp edges when fractured. 'Flint' is a specific variety of chert commonly found in chalk or marly limestone.
Field identification & locations
Identify by its waxy texture and distinctive conchoidal (shell-like) fracture patterns. It will scratch glass easily. Commonly found in riverbeds, limestone outcrops, or as smooth pebbles in coastal areas.
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