sedimentary
Chert Nodule (Iron-Stained)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs), Color: Rusty brown to reddish, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal
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Physical properties
Hardness: 7 (Mohs), Color: Rusty brown to reddish, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal
Formation & geological history
Formed via chemical precipitation of silica-rich fluids in sedimentary rock layers, often limestone or chalk. The iron staining occurs through oxidation (weathering).
Uses & applications
Abrasives, decorative landscaping, historical tool-making (flint knapping), and small sculpture carving.
Geological facts
Chert is so hard it can create sparks when struck against steel. It was one of the most important materials for early humans to create arrowheads and scrapers.
Field identification & locations
Identify by its smooth, waxy feel and the shell-like (conchoidal) fracture where pieces have chipped off. Commonly found in stream beds or within limestone outcrops.
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