sedimentary
Chert (Flint / Quartz Nodule)
Microcrystalline Quartz (SiO2)
Hardness of 7 on Mohs scale, waxy to dull luster, white to off-white/beige color with sharp conchoidal fracture edges and non-porous fine-grained texture.
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Physical properties
Hardness of 7 on Mohs scale, waxy to dull luster, white to off-white/beige color with sharp conchoidal fracture edges and non-porous fine-grained texture.
Formation & geological history
Formed via chemical precipitation of silica in marine sediment environments or secondary replacement of limestone/chalk beds by silica-rich fluids.
Uses & applications
Historically used for knapping sharp cutting tools and arrowheads; currently used in construction aggregate and as decorative landscape rock.
Geological facts
Chert produces sparks when struck against iron or steel, which made it vital for survival and flintlock firearms historically.
Field identification & locations
Identify by its hardness (scratches glass easily), smooth or shell-like conchoidal fracture surfaces, and opaque appearance. Commonly found embedded as nodules in limestone deposits.
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