sedimentary
Flint
Silicon Dioxide (SiO2)
Hardness: 7 on the Mohs scale. Color: Brown, grey, black, or yellowish. Luster: Waxy to vitreous. Crystal structure: Microcrystalline quartz (chalcedony). Cleavage: None, exhibits conchoidal fracture.
- Hardness
- 7 on the Mohs scale
- Color
- Brown, grey, black, or yellowish
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on the Mohs scale. Color: Brown, grey, black, or yellowish. Luster: Waxy to vitreous. Crystal structure: Microcrystalline quartz (chalcedony). Cleavage: None, exhibits conchoidal fracture.
Formation & geological history
Forms as nodules and masses in sedimentary rocks, primarily chalk and limestone, through the replacement of calcium carbonate by silica-rich groundwater over millions of years.
Uses & applications
Historically used for making stone tools, weapons, and fire-starting. Today used in landscaping, abrasive grit, and occasionally ornamental items.
Geological facts
Flint was one of the earliest materials manipulated by early humans to create sharp cutting edges and arrowheads due to its predictable conchoidal fracture.
Field identification & locations
Can be identified in the field by its conchoidal fracture, waxy luster, and ability to spark when struck against steel. Found globally within chalk and limestone formations.
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