sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5–7 (Mohs scale), Color: Dull greenish-grey to tan, Luster: Waxy to sub-vitreous, Crystal structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5–7 (Mohs scale), Color: Dull greenish-grey to tan, Luster: Waxy to sub-vitreous, Crystal structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation from hydrothermal fluids in sedimentary environments. Common in Paleozoic to Cenozoic strata.
Uses & applications
Historically used for stone tools and weapons due to its sharp edges when broken. Modern uses include jewelry (lapidary), abrasives, and landscape decor.
Geological facts
Chert is so hard it can strike sparks against steel. It was the primary material for arrowheads and scrapers for thousands of years throughout human prehistory.
Field identification & locations
Identify in the field by its characteristic smooth, curved (conchoidal) fracture surfaces and its ability to scratch glass. Commonly found in limestone beds or as river-worn pebbles.
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