sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 Mohs scale; Color: Brown, tan, grey; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 Mohs scale
- Color
- Brown, tan, grey
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 Mohs scale; Color: Brown, tan, grey; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed in marine environments as biological or chemical precipitates. This specimen likely formed as nodules within limestone or chalk beds during the Cretaceous period or earlier.
Uses & applications
Historically used for stone tools like arrowheads and fire-starting. Today used as a road aggregate, in landscaping, and as a collector's specimen.
Geological facts
Flint was arguably the most important resource for prehistoric humans due to its ability to break with sharp, glass-like edges. It produces sparks when struck against steel.
Field identification & locations
Identify in the field by its smooth, waxy texture and distinctive shell-like (conchoidal) fracture patterns. Frequently found in riverbeds, fields, and chalk cliffs.
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