sedimentary
Chert (River Pebble)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Olive green to yellowish-brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Olive green to yellowish-brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Olive green to yellowish-brown; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments. This specimen is water-worn, indicating transport in a river or stream over thousands of years.
Uses & applications
Historically used for stone tools due to its sharp edges when broken. Today used in landscaping, road construction aggregates, and occasionally as a decorative river stone.
Geological facts
Chert is extremely durable and chemically stable. Because it is harder than steel, it was a primary material for arrowheads and fire-starting 'flints' throughout human history.
Field identification & locations
Identify in the field by its smooth, waxy texture and characteristic shell-like (conchoidal) fractures. Common in sedimentary basins and riverbeds worldwide.
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