sedimentary
Chert
Chert (SiO2)
Hardness: 7 Mohs scale; Color: Grey, tan, brown; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6
- Hardness
- 7 Mohs scale
- Color
- Grey, tan, brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 Mohs scale; Color: Grey, tan, brown; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6
Formation & geological history
Formed via the accumulation of silica-rich biogenic material or chemical precipitation in marine environments; age spans from Precambrian to Holocene.
Uses & applications
Historically used for stone tools and weapons (arrowheads); used currently as construction aggregate and for lapidary work.
Geological facts
Archaeologists use chert samples to track ancient trade routes based on specific geochemical signatures and quarry sites.
Field identification & locations
Identified by its extreme hardness (cannot be scratched by steel) and sharp, shell-like (conchoidal) fractures; common in limestone beds worldwide.
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