sedimentary

Chert (Brown Variety)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brown, tan, waxy luster; Crystal Structure: Hexagonal (microscopic); Fracture: Conchoidal (shell-like); Opaque to translucent edges.

Hardness: 6
Color: Brown, tan, waxy luster

Identified July 4, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, tan, waxy luster; Crystal Structure: Hexagonal (microscopic); Fracture: Conchoidal (shell-like); Opaque to translucent edges.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation from silica-saturated fluids in limestone or chalk beds.

Uses & applications

Historically used for stone tools and arrowheads; used today in construction aggregate, as a gemstone (Jasper/Flint variants), and for fire-starting.

Geological facts

Chert is extremely durable and chemically stable. Flaked chert specimens are among the oldest artifacts found in human history, dating back millions of years.

Field identification & locations

Identify by its 'waxy' appearance and sharp, curved edges when broken. It will scratch glass and cannot be scratched by a steel knife. Commonly found in nodules within sedimentary rock layers.