sedimentary
Flint Pebble
Silicon dioxide (microcrystalline quartz / chalcedony)
Hardness: 7 on the Mohs scale; Color: Grey, white, or dark brown/black inside; Luster: Waxy to vitreous; Crystal structure: Microcrystalline/cryptocrystalline; Fracture: Conchoidal; Specific gravity: 2.60-2.65
- Hardness
- 7 on the Mohs scale
- Color
- Grey, white, or dark brown/black inside
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on the Mohs scale; Color: Grey, white, or dark brown/black inside; Luster: Waxy to vitreous; Crystal structure: Microcrystalline/cryptocrystalline; Fracture: Conchoidal; Specific gravity: 2.60-2.65
Formation & geological history
Forms by the replacement of calcium carbonate by silica-rich solutions in chalk or limestone formations during the Cretaceous period, followed by weathering and water-tumbles into smooth pebbles on beaches.
Uses & applications
Historically used for making stone tools, arrowheads, and fire-starting (flintlock firearms); today used as decorative gravel, in construction, and by rock collectors.
Geological facts
Flint is extremely durable and breaks with a very sharp conchoidal fracture, making it one of the most important materials used by early humans for stone tool technology.
Field identification & locations
Commonly found along chalk coastal beaches and riverbeds, easily identified by its smooth, water-worn exterior, waxy texture, and conchoidal chipping.
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