sedimentary
Weathered flint or chert fragment
Microcrystalline quartz (SiO₂), commonly called chert or flint
AI-generated identification · may be incorrectTypically Mohs hardness 6.5–7, dull to waxy luster, opaque gray-brown color, and conchoidal fracture without cleavage. The specimen appears weathered and may show a slightly lighter cortex; its exact identity is uncertain from the image alone.
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Physical properties
Typically Mohs hardness 6.5–7, dull to waxy luster, opaque gray-brown color, and conchoidal fracture without cleavage. The specimen appears weathered and may show a slightly lighter cortex; its exact identity is uncertain from the image alone.
Formation & geological history
Chert forms when silica-rich groundwater replaces or cements sediment, often in limestone or chalk, through diagenesis. Formation ages range from Precambrian to recent, depending on its host sediment.
Uses & applications
Used historically for stone tools and fire-starting, and occasionally as decorative or landscaping stone; this irregular fragment has little commercial value.
Geological facts
Sharp, curved conchoidal edges are characteristic of quartz-rich chert and can resemble volcanic glass, though chert is generally less glassy and more waxy.
Field identification & locations
Look for hardness sufficient to scratch ordinary glass, no visible grains, and curved fracture surfaces; common sources include chalk and limestone regions worldwide. Avoid confusing it with slag or dark volcanic rock.