sedimentary
Chert (Jasper/Flint variety)
Microcrystalline quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan to yellowish-brown with dark grey/black inclusions; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan to yellowish-brown with dark grey/black inclusions
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan to yellowish-brown with dark grey/black inclusions; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); 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. Its rounded shape indicates it was water-worn in a river or beach environment over thousands of years.
Uses & applications
Historically used for stone tools (arrowheads) due to sharp edges; currently used for landscaping, as a minor gemstone (if patterned), and in construction aggregates.
Geological facts
Chert is so hard it can scratch steel. It was one of the most important minerals for early humans because of its ability to fracture into extremely sharp blades.
Field identification & locations
Identify by its waxy luster, smoothness, and conchoidal (shell-like) fracture patterns if chipped. Commonly found in riverbeds and limestone outcrops. Collectors look for unique banding or dendritic patterns.
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