sedimentary
Chert (Vuggy Chert)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Gray/brown with white weathering, Luster: Dull to waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Features: Vuggy (contains small cavities)
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Physical properties
Hardness: 7 (Mohs scale), Color: Gray/brown with white weathering, Luster: Dull to waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Features: Vuggy (contains small cavities)
Formation & geological history
Formed through the precipitation of silica from seawater or groundwater within existing limestone or chalk beds. Often associated with Paleozoic or Mesozoic era deposits.
Uses & applications
Historically used for stone tools (flint); currently used in road construction, as an abrasive, and for lapidary collection.
Geological facts
Chert is so hard it can scratch steel. This particular specimen shows 'vugs' or pores, which can sometimes be filled with secondary mineral crystals like quartz or calcite.
Field identification & locations
Look for a smooth, waxy fracture surface and extreme hardness. Commonly found in riverbeds, glacial tills, and as nodules in limestone outcrops.
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