sedimentary
Chert (Jasper/Flint variant)
Microcrystalline or cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, or pale green; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, or pale green
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, or pale green; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or by chemical precipitation in marine environments during various geological eras from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools and weapons due to sharp edges; currently used for road surfacing, landscape stone, and occasionally lapidary art.
Geological facts
Chert was one of the most important minerals for early humans, used to create arrowheads, spear points, and scrapers because it breaks in predictable, sharp flakes.
Field identification & locations
Identify in the field by its smooth, waxy texture and shell-like (conchoidal) fracture pattern when broken. It cannot be scratched by a steel knife and often produces a spark when struck with steel.
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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