sedimentary
Banded Chert
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5-7; Color: Yellow, tan, and brown with dark purple/grey mineral bands; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6
- Hardness
- 6
- Color
- Yellow, tan, and brown with dark purple/grey mineral bands
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7; Color: Yellow, tan, and brown with dark purple/grey mineral bands; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, often associated with Precambrian formations or secondary replacement in limestone.
Uses & applications
Used historically for stone tools (lithics); currently used in lapidary work, jewelry, and as decorative gravel.
Geological facts
The banding in chert can represent seasonal rhythms in deposition or changes in ocean chemistry; chert is so durable it can survive millions of years of erosion and river transport.
Field identification & locations
Identify by its waxy texture, bands that follow the rock's layering, and its ability to scratch glass. Commonly found in riverbeds and sedimentary basins worldwide.
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