sedimentary
Chert (Jasper) pebble
Microcrystalline Quartz (SiO2)
Hardness 7 on Mohs scale, waxy to dull luster, conchoidal fracture, fine-grained microcrystalline texture. Colors vary from reddish-brown to grayish-blue.
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Physical properties
Hardness 7 on Mohs scale, waxy to dull luster, conchoidal fracture, fine-grained microcrystalline texture. Colors vary from reddish-brown to grayish-blue.
Formation & geological history
Formed from the precipitation of silica-rich fluids or accumulation of siliceous organism remains (like radiolarians) in marine or lacustrine environments.
Uses & applications
Historically used for stone tools and fire-striking; currently used as ornamental stones, landscaping pebbles, and in lapidary work.
Geological facts
Chert has been used since prehistoric times for making arrowheads and spear points due to its sharp conchoidal fracture edges.
Field identification & locations
Can be identified by its hardness (scratches glass), waxy luster, smooth conchoidal fracture surfaces, and multi-colored rind or core. Commonly found in riverbeds, gravel deposits, and sedimentary limestone formations worldwide.
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