sedimentary

Banded Chert

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Brown, tan, and dark grey banding; Luster: Dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7

Hardness: 6
Color: Brown, tan, and dark grey banding
Luster: Dull to waxy

Identified July 7, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, tan, and dark grey banding; Luster: Dull to waxy; Structure: Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. The banding represents changes in sediment supply or oxygen levels over millions of years.

Uses & applications

Historically used for stone tools (arrowheads). Modernly used in landscaping, as an abrasive, and by rock hounds for lapidary work.

Geological facts

Chert is so hard it can scratch steel. When struck against steel, it can produce sparks, similar to its close relative, flint.

Field identification & locations

Identify by its horizontal layering (banding), smooth waxy feel when wet, and sharp edges when broken. Frequently found in riverbeds or within limestone and dolostone formations.