sedimentary
Chert (specifically Flint Arrowhead)
Silicon dioxide (SiO2) - Microcrystalline Quartz
Hardness: 7 (Mohs scale); Color: dark gray, black, or bluish-gray; Luster: waxy to vitreous; Structure: Cryptocrystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- dark gray, black, or bluish-gray
- Luster
- waxy to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: dark gray, black, or bluish-gray; Luster: waxy to vitreous; Structure: Cryptocrystalline; Cleavage: none (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation in sedimentary environments such as limestone or chalk beds. Often Cretaceous in age.
Uses & applications
Historically used for stone tools and weapons (arrowheads, scrapers, knives) and as a strike-a-light for fire making. Currently used as an abrasive or in construction aggregates.
Geological facts
Flint was the first 'high-tech' material of prehistoric man due to its predictability when knapped. The arrow-like shape of this specimen indicates it is an anthropogenic artifact, not just a raw geological find.
Field identification & locations
Identify by its characteristic conchoidal (shell-like) fracture patterns and sharp edges. In the field, look for 'nodules' within host limestone units or as surface gravels.
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