sedimentary
Chert
Microcrystalline or cryptocrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7, Color: variable (greenish, brown, gray, yellow), Luster: waxy to dull, Crystal structure: microcrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.59-2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7, Color: variable (greenish, brown, gray, yellow), Luster: waxy to dull, Crystal structure: microcrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.59-2.65
Formation & geological history
Forms as a chemical sedimentary rock or through the replacement of other materials, often in marine environments from siliceous oozes or within limestone formations.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) due to its conchoidal fracture. Sometimes used as a semi-precious stone in tumbling or lapidary work.
Geological facts
Flint, a variety of chert, was crucial to early human survival for tool making and starting fires. Jasper is another colorful variety.
Field identification & locations
Identified by its waxy luster, hardness (scratches glass), and conchoidal fracture. Often found as nodules in limestone or as extensive bedded deposits.
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