sedimentary
Chert (Pink/Tan variety)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Pinkish-tan with gray patches, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: Pinkish-tan with gray patches, Luster: Waxy to dull, Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture)
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. Often occurs as nodules or layers within limestone or shale.
Uses & applications
Historically used for stone tools and arrowheads; currently used in construction aggregate, road surfacing, and as decorative landscaping stone.
Geological facts
Chert is nearly identical to flint; the main difference is color, with flint usually being dark and chert being lighter. It has a distinctive sharp edge when broken.
Field identification & locations
Identify by its ability to scratch glass, its waxy texture, and its smooth, shell-like (conchoidal) fracture pattern. Commonly found in sedimentary basins and riverbeds.
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