sedimentary
Chert (Flint Gravel)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: yellowish-brown, tan, gray; Luster: waxy to dull; Fracture: conchoidal; Density: ~2.65 g/cm³.
- Hardness
- 7 on Mohs scale
- Color
- yellowish-brown, tan, gray
- Luster
- waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: yellowish-brown, tan, gray; Luster: waxy to dull; Fracture: conchoidal; Density: ~2.65 g/cm³.
Formation & geological history
Formed by the precipitation of silica from groundwater or the accumulation of siliceous organism remains in shallow marine or freshwater sedimentary environments.
Uses & applications
Commonly used as construction aggregate, landscaping gravel, and historically for making sharp stone tools and starting fires.
Geological facts
Chert is extremely durable and weather-resistant, which is why small pebbles of it frequently survive erosion and end up as common surface gravel.
Field identification & locations
Identified by its high hardness (scratches glass) and smooth, shell-like (conchoidal) fracture surfaces. Commonly found in riverbeds, gravel driveways, and soil deposits.
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