sedimentary
Chert (specifically Flint or Novaculite variant)
Chert (Microcrystalline Quartz, SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Tan, beige, or white; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Tan, beige, or white
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Tan, beige, or white; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like diatoms or radiolarians) or through the chemical replacement of limestone/dolomite by silica-rich fluids. Can be found in Paleozoic to Cenozoic strata.
Uses & applications
Historical use for stone tools (knapping) and fire-starting (flint); modern use as industrial abrasives, road surfacing, or as a gemstone if colorful.
Geological facts
Chert was one of the most vital materials for early humans because its conchoidal fracture creates razor-sharp edges useful for knives, scrapers, and arrowheads. This specimen appears to be a 'debitage' flake or a crude lithic tool.
Field identification & locations
Identify by its 'glassy' waxy texture, extreme hardness (scratches glass), and shell-like (conchoidal) curved fracture patterns. Commonly found in limestone outcrops or as nodules in riverbeds.
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