sedimentary
Banded Chert Pebble
SiO2 (Microcrystalline Quartz)
Hardness 6.5-7 on Mohs scale, waxy to dull luster, cryptocrystalline structure, conchoidal fracture, dark gray to black and tan/cream alternating bands.
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Physical properties
Hardness 6.5-7 on Mohs scale, waxy to dull luster, cryptocrystalline structure, conchoidal fracture, dark gray to black and tan/cream alternating bands.
Formation & geological history
Formed in marine environment by accumulation of siliceous organism remains or chemical precipitation, subsequent diagenesis, followed by river or coastal erosion into a smooth pebble.
Uses & applications
Decorative pebble, tumbled stones, landscaping, educational geological sample.
Geological facts
Chert has been used since prehistoric times to make sharp tools, arrowheads, and spark-producing fire-starters due to its conchoidal fracturing behavior.
Field identification & locations
Identified by distinct alternating dark and light silica bands, smooth water-worn surface, and scratch resistance against steel. Common in gravel beds, rivers, and coastal beaches.
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