sedimentary

Banded Chert (Flint)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: Tan, brown, and cream bands; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Tan, brown, and cream bands
Luster: Waxy to vitreous

Identified June 28, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, brown, and cream bands; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like diatoms or radiolaria) or chemical precipitation in marine environments. The banding represents Different levels of impurities like iron oxides during deposition.

Uses & applications

Historically used for stone tools and weapons due to its sharp edges. Currently used in jewelry (lapidary), as abrasives, and as architectural decorative stone.

Geological facts

Chert was one of the most important minerals for early humans to create fire-starting tools and sharp arrowheads. It is extremely durable and weather-resistant.

Field identification & locations

Look for a smooth, waxy texture and conchoidal (shell-like) fractures. It is commonly found in limestone or chalk beds. Collectors should look for clear, consistent banding and lack of cracks.