sedimentary

Chert (specifically varieties like Chalcedony or Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Waxy white, grey, beige with slight translucency; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 (Mohs scale)
Color: Waxy white, grey, beige with slight translucency
Luster: Vitreous to waxy

Identified July 12, 2026More sedimentary →

Explore Chert (specifically varieties like Chalcedony or Flint) in the encyclopedia →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Common in limestone or chalk beds, often dating from the Paleozoic to Mesozoic eras.

Uses & applications

Used historically for stone tools (knapping), flintlock firearms, and modern decorative stones. High-quality colorful specimens are used in jewelry as cabochons.

Geological facts

Chert breaks with a conchoidal fracture, creating sharp edges that were essential for arrowhead and scraper manufacturing by prehistoric humans.

Field identification & locations

Identify by its waxy appearance, extreme hardness (scratches glass), and the curved or scalloped way it breaks. Look for it in river beds or errodable limestone outcrops.