sedimentary
Chert Pebble
Chert (Silicon Dioxide, SiO2)
Hardness: 7 on Mohs scale; Color: Gray to tan with weather patina; Luster: Dull to waxy; Structure: Microcrystalline; Conchoidal fracture; Specific gravity: approx 2.6
- Hardness
- 7 on Mohs scale
- Color
- Gray to tan with weather patina
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray to tan with weather patina; Luster: Dull to waxy; Structure: Microcrystalline; Conchoidal fracture; Specific gravity: approx 2.6
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments; age varies from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools (arrowheads); currently used in road gravel, as grinding media, or tumbled for decorative use.
Geological facts
Chert has a conchoidal fracture which allows it to break into very sharp edges, making it the primary material for prehistoric survival tools.
Field identification & locations
Identify by its hardness (it will scratch glass) and its smooth, shell-like fracture surfaces; very common in riverbeds and limestone outcrops.
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