sedimentary
Chert (Flint)
Chert (Cryptocrystalline Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: Gray, tan, white, or black; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Gray, tan, white, or black
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, tan, white, or black; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine or groundwater environments. This specimen appears to be a nodule often found in limestone or chalk beds.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to its sharp edges; modern uses include road surfacing, jewelry as a semi-precious stone, and as a component in glassmaking.
Geological facts
Because it produces sparks when struck against steel, it was essential for flintlock firearms and early fire-starting tools. It is one of the most common materials used by prehistoric humans.
Field identification & locations
Identified by its waxy texture and shell-like (conchoidal) fractures that create razor-sharp edges. It is frequently found as nodules within sedimentary rock layers like limestone.
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