sedimentary
Banded Chert
Chert (Silicon Dioxide, SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: Swirls of dark brown, black, and tan; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Swirls of dark brown, black, and tan
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Swirls of dark brown, black, and tan; Luster: Waxy to vitreous; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation from groundwater within sedimentary layers. Over time, heat and pressure compress these layers into dense rock.
Uses & applications
Commonly used for lapidary work, decorative stones, and historically for stone tools like scrapers and arrowheads due to its sharp edges when broken.
Geological facts
This specimen is a water-worn or tumbled pebble showcasing distinct sedimentary banding. Chert is extremely durable and chemically resistant to weathering.
Field identification & locations
Identify it by its smooth, waxy feel, hardness (it will scratch glass), and the circular (conchoidal) patterns where it has chipped. Often found in riverbeds or coastal deposits.
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