sedimentary
Chert (or potentially Jasper/Chalcedony)
SiO2 (Silicon Dioxide)
Hardness: 6.5-7 (Mohs scale), Color: Grayish to greenish, Luster: Waxy to dull, Crystal structure: Microcrystalline quartz, Cleavage: None (conchoidal fracture), Specific gravity: 2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Grayish to greenish, Luster: Waxy to dull, Crystal structure: Microcrystalline quartz, Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed from silica-rich fluids precipitating in sedimentary rock environments such as limestone or chalk, often taking millions of years to form.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) due to its conchoidal fracture. Sometimes used as an abrasive or in construction, and polished for lapidary uses.
Geological facts
Chert has been a remarkably important rock in human history because of its ability to hold a sharp edge, making it one of the earliest materials used for tool-making.
Field identification & locations
Identified by its hard, slightly waxy surface and conchoidal fractures. Commonly found in riverbeds, glacial till, and sedimentary rock formations worldwide.
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