sedimentary
Chert (Flint/Jasper variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Tan, orange-brown, and white due to iron oxide staining. Luster: Dull to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Tan, orange-brown, and white due to iron oxide staining
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Tan, orange-brown, and white due to iron oxide staining. Luster: Dull to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed by the accumulation of siliceous remains of marine organisms or through chemical precipitation of silica-rich fluids in limestone or chalk beds. Often Paleozoic or Mesozoic in age.
Uses & applications
Historically used for stone tools (arrowheads). Modern uses include road surfacing, decorative gravel, and lapidary work if colorful (as jasper).
Geological facts
Chert is so hard it can scratch glass and steel. It was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges.
Field identification & locations
Identified by its hardness, smooth waxy feel on breaks, and sharp edges. It is common in riverbeds and limestone outcrops globally. Look for smooth, rounded nodules or jagged pieces with a 'clinking' sound when struck.
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