sedimentary

Chert (Commonly called Jasper or Flint)

Chert (SiO2)

AI-generated identification · may be incorrect

Hardness: 7.0 (Mohs scale), Color: Brown, tan, and earthy tones with waxy luster. Crystal structure: Microcrystalline (Cryptocrystalline). Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Hardness: 7
Color: Brown, tan, and earthy tones with waxy luster

Identified June 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via the accumulation of silica-rich organic remains or chemical precipitation from groundwater within sedimentary layers like limestone or chalk. Many deposits date back to the Paleozoic or Mesozoic eras.

Uses & applications

Used historically for stone tools and weapons due to its sharp edges. Modern uses include road surfacing, decorative garden stones, and occasionally lapidary work for jewelry if colorful enough.

Geological facts

Because it breaks with a conchoidal fracture like glass, it was the primary material used by prehistoric humans for arrowheads and scrapers. It can spark when struck against steel.

Field identification & locations

Identify by extreme hardness (scratches glass), waxy to dull luster, and absence of visible crystals. Found globally in riverbeds, glacial tills, and sedimentary rock outcrops.