sedimentary
Chert (Flint Nodules)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Grey, brown, black; Luster: Waxy to dull; Structure: Cryptocrystalline; Fracture: Conchoidal (shell-like curves); Cleavage: None.
- Hardness
- 6
- Color
- Grey, brown, black
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Grey, brown, black; Luster: Waxy to dull; Structure: Cryptocrystalline; Fracture: Conchoidal (shell-like curves); Cleavage: None.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or sponges) within limestone or chalk beds. Often occurs as nodules or beds in sedimentary strata dating from Precambrian to modern times.
Uses & applications
Historically used for stone tools and weapons (arrowheads). Modernly used in road construction, as striking stones for flintlock mechanisms, and as decorative gravel.
Geological facts
Flint is a variety of chert that specifically forms in chalk or marly limestone. It was the primary material used during the Stone Age for creating sharp cutting edges.
Field identification & locations
Identify in the field by its sharp, curved edges when broken and its ability to scratch glass. Found globally in areas with sedimentary limestone deposits, such as the White Cliffs of Dover.
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