sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Yellowish-orange/Tan with iron staining; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Yellowish-orange/Tan with iron staining
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Yellowish-orange/Tan with iron staining; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the accumulation of silica-rich microfossils or via chemical precipitation in sedimentary environments. Its age can range from Precambrian to recent times.
Uses & applications
Historically used for stone tools and arrowheads; currently used as landscaping stone, abrasive, or for lapidary work (jewelry and cabochons).
Geological facts
Chert was one of the most vital materials for early humans due to its ability to fracture into sharp edges. The yellow/orange color is typically caused by goethite or limonite impurities.
Field identification & locations
Identify by its waxy appearance and shell-like (conchoidal) fracture pattern. It will scratch glass easily. Found globally in limestone and chalk beds or as gravel in riverbeds.
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