sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 Mohs scale; Color: Dark grey, charcoal, and brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None, exhibits conchoidal fracture; Specific Gravity: 2.65.
- Hardness
- 7 Mohs scale
- Color
- Dark grey, charcoal, and brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 Mohs scale; Color: Dark grey, charcoal, and brown; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None, exhibits conchoidal fracture; Specific Gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation from groundwater within sedimentary beds. These specimens often originate from limestone or chalk formations and can date back hundreds of millions of years.
Uses & applications
Historically used for stone tools and weapons (arrowheads). Modern uses include road surfacing, decorative landscaping, and as fire-starting flints in survival kits.
Geological facts
Because it breaks with sharp, shell-like (conchoidal) edges, it was the primary material for the Stone Age technology. It is extremely resistant to chemical weathering.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, curved conchoidal fracture surfaces. Commonly found in riverbeds or within limestone outcrops.
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