sedimentary
Chert (Light Variety)
Sedimentary cryptocrystalline quartz (SiO2)
Hardness: 7 (Mohs scale); Color: Creamy white to light tan; Luster: Dull to waxy; Texture: Fine-grained with conchoidal (shell-like) fracture edges; Cleavage: None.
- Hardness
- 7 (Mohs scale)
- Color
- Creamy white to light tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 (Mohs scale); Color: Creamy white to light tan; Luster: Dull to waxy; Texture: Fine-grained with conchoidal (shell-like) fracture edges; Cleavage: None.
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine or freshwater environments during various geological eras from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools (knapping for scrapers or arrowheads) due to its sharp fracture edges. Today it is used as road aggregate or as a lapidary material if it contains colorful patterns.
Geological facts
Chert is so hard it can scratch steel and was used for centuries as a flint to start fires when struck against steel. This specific light-colored variety is often found in limestone or dolostone layers.
Field identification & locations
Identify by its extreme hardness and the smooth, curved surfaces where it has broken. Commonly found in outcroppings of sedimentary rock or as river-worn pebbles. For collectors, look for sharp edges and density.
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