sedimentary
Chert (Jasper-like Silicate)
Microcrystalline quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and yellowish-grey with earthy coating. Luster: Dull to waxy. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Tan, brown, and yellowish-grey with earthy coating
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and yellowish-grey with earthy coating. Luster: Dull to waxy. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Can be found in nodules within limestone or as massive bedded deposits. Geological age varies from Precambrian to modern.
Uses & applications
Historically used for stone tools (arrowheads/scrapers) due to sharp edges; used today as a decorative stone, in construction aggregate, or as an abrasive.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture creates edges sharper than a steel scalpel. It is highly resistant to chemical weathering.
Field identification & locations
Identify by its hardness (it will scratch glass), its sharp angular edges when broken, and its smooth, waxy interior surface if chipped. Commonly found in riverbeds or within limestone outcrops.
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