sedimentary
Chert (Jasper Pebble)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness 6.5–7 on the Mohs scale, waxy to dull luster, conchoidal fracture, and a smooth water-worn surface.
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Physical properties
Hardness 6.5–7 on the Mohs scale, waxy to dull luster, conchoidal fracture, and a smooth water-worn surface.
Formation & geological history
Formed via chemical precipitation of silica in sedimentary environments or hydrothermal voids, later rounded by alluvial erosion.
Uses & applications
Used historically for flint knapping and tools; today collected as tumbled stones, ornamental pebbles, or lapidary rough.
Geological facts
Because of its fine grain and high hardness, naturally tumbled chert pebbles are virtually indestructible in riverbeds.
Field identification & locations
Identified by hardness (scratches glass), lack of cleavage, and smooth alluvial polish; ubiquitous in gravel deposits and beaches.
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