sedimentary

Banded Chert (Flint/Jasper variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Multi-colored bands (dark gray, black, brown, tan); Luster: Vitreous to waxy; Crystal Structure: Cryptocrystalline/Trigonal (detectable under high magnification); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Multi-colored bands (dark gray, black, brown, tan)
Luster: Vitreous to waxy

Identified March 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids in marine environments. Banding represents different mineral impurities or varying deposition rates over thousands to millions of years.

Uses & applications

Used historically for stone tools due to its sharp edges; modernly used as a decorative gemstone, in tumbling/lapidary hobbies, and as an industrial abrasive.

Geological facts

Banded chert is often associated with Banded Iron Formations (BIFs), some of which date back over 2 billion years and provide evidence of the 'Great Oxygenation Event' in Earth's history.

Field identification & locations

Identify in the field by its smooth, waxy texture and shell-like (conchoidal) fractures where broken. It is harder than steel and will scratch glass. Look for it in riverbeds or coastal deposits. Found globally, with notable deposits in the Lake Superior region (USA) and Brazil.