sedimentary
Chert (White Chert / Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Creamy white to pale tan; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 – 2.7
- Hardness
- 7 on Mohs scale
- Color
- Creamy white to pale tan
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Creamy white to pale tan; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 – 2.7
Formation & geological history
Formed through the accumulation of siliceous remains of organisms (like diatoms or radiolarians) or by chemical precipitation of silica-rich fluids. It typically occurs as nodules or layers in limestone or chalk beds spanning various geological ages from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools and arrowheads due to its sharp edges. Modern uses include road surfacing, decorative landscaping, and as a raw material in some ceramics.
Geological facts
Chert and its variety Flint were the most important technological materials for early humans, used for starting fires and crafting lethal weaponry. It is so tough that it was commonly used as flintlock ignition for early firearms.
Field identification & locations
Identify in the field by its distinctive 'seashell-like' (conchoidal) fracture pattern and its ability to scratch glass. It is commonly found in sedimentary basins worldwide. Collectors look for sharp edges and smooth, waxy surfaces.
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