sedimentary
Flint
Microcrystalline Quartz (SiO2)
Hardness: 7 on the Mohs scale. Color: Dark grey, black, or brown. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic quartz crystals). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.60-2.65.
- Hardness
- 7 on the Mohs scale
- Color
- Dark grey, black, or brown
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on the Mohs scale. Color: Dark grey, black, or brown. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic quartz crystals). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.60-2.65.
Formation & geological history
Formed by the chemical replacement of calcium carbonate in limestone or chalk by silica-rich solutions during diagenesis. Geological age ranges widely, often found in Cretaceous chalk deposits.
Uses & applications
Historically used for making stone tools, arrowheads, and striking fire. Occasionally used in construction and decorative landscaping.
Geological facts
Flint breaks with a very sharp conchoidal fracture, making it ideal for knapping into tools. It was one of the earliest materials manipulated by early humans.
Field identification & locations
Easily identified by its dark color, waxy luster, conchoidal fracture, and ability to spark when struck against steel. Found globally in chalk and limestone formations.
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