sedimentary
Chert (specifically Flint or Jasper variant)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Brown, tan, or reddish-brown; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 6
- Color
- Brown, tan, or reddish-brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, tan, or reddish-brown; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolaria) or through chemical precipitation in sedimentary environments. Can be found in limestone or chalk beds.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to its sharp edges; used today in road construction, as a high-silica industrial material, and occasionally in jewelry as Jasper.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture allows it to be shaped into incredibly sharp tools. This specific piece appears to show 'knapping' or intentional flaking, suggesting it might be an archaeological lithic flake.
Field identification & locations
Identify in the field by its waxy texture and shell-like (conchoidal) fractures. It is much harder than steel and cannot be scratched by a knife. Common in riverbeds and limestone outcrops.
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