sedimentary
Chert Pebble
Microcrystalline Quartz (SiO2)
Hardness 7 on Mohs scale; color is muted grey to tan; dull to waxy luster; conchoidal fracture; dense microcrystalline structure; specific gravity 2.6-2.7.
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Physical properties
Hardness 7 on Mohs scale; color is muted grey to tan; dull to waxy luster; conchoidal fracture; dense microcrystalline structure; specific gravity 2.6-2.7.
Formation & geological history
Formed through the precipitation of silica in sedimentary environments or by the replacement of calcium carbonate in limestone. This specimen appears water-worn, likely from a stream or coastal environment.
Uses & applications
Historically used for stone tools and flints. Today used as decorative gravel, in road construction, and for aquarium or garden decor.
Geological facts
Chert is one of the most durable sedimentary rocks. It was the primary material used by prehistoric humans to create arrowheads and knives because it breaks into sharp edges.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, waxy surface when polished or wet. Found ubiquitously in gravel pits and riverbeds.
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