sedimentary
Banded Chert / Agate Pebble
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, beige, and cream in concentric/wavy bands. Luster: Waxy to dull (smooth stream-worn surface). Cleavage: None (conchoidal fracture). Specific Gravity: ~2.65.
- Hardness
- 6
- Color
- Tan, brown, beige, and cream in concentric/wavy bands
- Luster
- Waxy to dull (smooth stream-worn surface)
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, beige, and cream in concentric/wavy bands. Luster: Waxy to dull (smooth stream-worn surface). Cleavage: None (conchoidal fracture). Specific Gravity: ~2.65.
Formation & geological history
Formed by precipitation of microcrystalline quartz or silica-rich fluid deposition in sedimentary rocks or volcanic cavities. Weathered out and stream-tumbled into a smooth pebble over thousands to millions of years.
Uses & applications
Lapidary projects, tumbling, decorative landscaping, and amateur rockhounding collecting.
Geological facts
Banded chert and agates are extremely durable microcrystalline quartz specimens. Due to high silica content, early humans frequently used chert and chalcedony for crafting sharp tools such as arrowheads, scrapers, and blades.
Field identification & locations
Look for distinct swirling or concentric bands with a smooth, waxy feel and lack of visible mineral grains. Commonly found in riverbeds, gravel pits, beaches, and glacial till worldwide.
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