sedimentary
Brown chert (flint)
Microcrystalline quartz (SiO₂), commonly called chert; the specimen may be iron-stained
AI-generated identification · may be incorrectHardness about 7 Mohs; opaque ochre-brown color, dull to waxy luster, and no visible crystals or cleavage. Typically breaks with smooth, curved conchoidal fractures and sharp edges; specific gravity about 2.6.
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Physical properties
Hardness about 7 Mohs; opaque ochre-brown color, dull to waxy luster, and no visible crystals or cleavage. Typically breaks with smooth, curved conchoidal fractures and sharp edges; specific gravity about 2.6.
Formation & geological history
Forms when silica accumulates and replaces material in sedimentary rocks, often limestone or chalk. Its age varies widely; the image alone cannot determine the specimen’s age or exact origin.
Uses & applications
Used historically for stone tools and fire-starting; today collected and occasionally used in decorative stonework or lapidary pieces.
Geological facts
Chert is a broad term for fine-grained silica rock; flint is a commonly used name for dark or otherwise workable chert.
Field identification & locations
Look for very fine texture, hardness sufficient to scratch glass, and conchoidal fracture. Chert occurs worldwide in sedimentary formations; this image does not establish a specific locality.
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