sedimentary
Banded Chert
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 Mohs; Color: Alternating layers of gray, tan, and cream; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.6
- Hardness
- 6
- Color
- Alternating layers of gray, tan, and cream
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: Alternating layers of gray, tan, and cream; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.6
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolarians or diatoms) or by chemical precipitation in marine environments; often undergoes lithification over millions of years.
Uses & applications
Historically used for stone tools/arrowheads due to conchoidal fracture; currently used for decorative stones, landscaping, and lapidary polishing.
Geological facts
Banded chert is often associated with some of the oldest known fossils on Earth, such as stromatolites found in Precambrian formations.
Field identification & locations
Identify by its hardness (can scratch glass), smooth waxy texture, and distinct layering. Common in sedimentary basins and as river-worn pebbles.
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