sedimentary
Chert Pebble
Chert (Microcrystalline Quartz, SiO2)
Hardness: 7 on Mohs scale; Color: Tan, yellowish-brown, or buff; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Tan, yellowish-brown, or buff
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, yellowish-brown, or buff; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This specimen shows significant rounding from water erosion (fluvial or beach action).
Uses & applications
Historically used for stone tools due to sharp edges; currently used for road surfacing, as an abrasive, and by hobbyists for rock tumbling.
Geological facts
Chert was one of the most important minerals for early humans to create arrowheads and scrapers. Its ability to produce sparks when struck against steel made it essential for flintlock firearms and fire-starting.
Field identification & locations
Identify by its hardness (scratches glass), waxy feel, and smooth surfaces where chipped. Common in riverbeds, glacial till, and coastal deposits. Collectors look for specific patterns or fossils within the matrix.
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