sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and grey with possible waxy luster. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.
- Hardness
- 6
- Color
- Tan, brown, and grey with possible waxy luster
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and grey with possible waxy luster. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.
Formation & geological history
Formed through the precipitation of silica-rich fluids within sedimentary rock layers or the accumulation of siliceous skeletal remains. Can range from Precambrian to recent geological ages.
Uses & applications
Historically used for stone tools and weapons due to sharp edges; currently used for lapidary work, jewelry, and as a component in construction aggregate.
Geological facts
Chert was one of the most important minerals for early humans, used to create arrowheads and scrapers. It can even create sparks when struck against steel, similar to flint.
Field identification & locations
Identify in the field by its conchoidal (shell-like) fracture patterns and ability to scratch glass. Found globally in limestone and chalk beds or as river-transported cobbles.
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