sedimentary
Chert / Flint Pebble
Silicon Dioxide (SiO2)
Hardness: 7; Color: Grayish-brown; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 7
- Color
- Grayish-brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 7; Color: Grayish-brown; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed from the accumulation of siliceous remains of organisms or precipitation from hydrothermal fluids, typically within limestone or chalk beds. Often found in riverbeds as water-worn pebbles.
Uses & applications
Historically used for tools and fire-starting; currently used as road aggregate, in landscaping, and some decorative lapidary work.
Geological facts
Because of its microcrystalline structure, chert fractures with very sharp edges (conchoidal), making it a primary material for prehistoric arrowheads and tools.
Field identification & locations
Identify by its hardness (scratches glass), waxy feel, and smooth curved fracture surfaces. Found worldwide in sedimentary basins and river gravels.
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