sedimentary
Chert (Honey Chert or Chalcedony Pebble)
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Waxy brown, honey-yellow, tan; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
- Hardness
- 6
- Color
- Waxy brown, honey-yellow, tan
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Waxy brown, honey-yellow, tan; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.65
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolarians or diatoms) or by chemical precipitation in marine or groundwater environments. This specimen appears water-worn, likely from a river or glacial deposit.
Uses & applications
Historically used for making stone tools (flint knapping) due to its sharp edges; used today as decorative river rock, landscaping, or as tumbled stones for hobbyists.
Geological facts
Chert is incredibly durable and resistant to chemical weathering. It was one of the most important minerals for early humans, used for arrowheads, scrapers, and fire-starting (flint is a variety of chert).
Field identification & locations
Identify in the field by its waxy texture and conchoidal (shell-shaped) fracture marks. It will scratch glass but cannot be scratched by a steel knife. Common in gravel pits and riverbeds.
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