sedimentary
Chert (Yellow Jasper/Flint)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Yellowish-brown and gray; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Yellowish-brown and gray
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Yellowish-brown and gray; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed via the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from groundwater within sedimentary beds. These are found in strata ranging from Precambrian to recent times.
Uses & applications
Used historically for tool making (arrowheads/scrapers), as fire-starters (flint), and modernly in jewelry as tumbles, cabochons, and decorative gravel.
Geological facts
Chert and flint were among the first materials used by early humans to create sharp-edged tools due to their conchoidal fracturing. Yellow varieties are often referred to as Jasper.
Field identification & locations
Identified by its signature curved (conchoidal) fracture surfaces and its ability to scratch glass. It is commonly found in riverbeds, glacial tills, and limestone formations globally.
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