sedimentary

Chert (Septarian or Banded Nodular Variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs scale; Color: Dark brown, tan, and creamy white; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Dark brown, tan, and creamy white
Luster: Dull to waxy

Identified June 7, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs scale; Color: Dark brown, tan, and creamy white; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed through the accumulation of silica-rich fluids within sedimentary host rocks, often as nodules or replacement layers. These patterns can form through dehydration and mineral infilling during diagenesis.

Uses & applications

Historically used for making stone tools (arrowheads/scrapers) due to conchoidal fracture. Modern uses include landscaping, or semi-precious lapidary work for unique patterns.

Geological facts

This specimen displays characteristics of Septarian nodules or jasper-like chert banding. Chert is so durable it can survive millions of years of weathering, often found in riverbeds long after the surrounding rock has eroded.

Field identification & locations

Identify by its hardness (it will scratch steel and glass) and the smooth, curved surfaces where it has broken. Commonly found in limestone or chalk beds globally.