sedimentary
Banded Agate
Silicon Dioxide (SiO2) - Variety of Chalcedony
Hardness: 6.5-7 (Mohs); Color: Waxy translucent honey-yellow with brown and white banding; Luster: Vitreous to waxy; Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None; Fracture: Conchoidal.
- Hardness
- 6
- Color
- Waxy translucent honey-yellow with brown and white banding
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Waxy translucent honey-yellow with brown and white banding; Luster: Vitreous to waxy; Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None; Fracture: Conchoidal.
Formation & geological history
Formed as a secondary mineral in cavities of volcanic rocks or sedimentary deposits. Silica-rich fluids deposit layers over time, creating distinctive banding. These specimens are often millions of years old.
Uses & applications
Commonly used in jewelry, as cabochons, for ornamental carving, or as collectibles. Industrial uses include burnishing tools due to its hardness.
Geological facts
Agate is named after the Achates River in Sicily where it was first discovered. The banding represents rhythmic crystallization pulses during its formation.
Field identification & locations
Identify by its waxy luster, translucency, and parallel banding. Commonly found in riverbeds, glacial tills, and volcanic regions globally (notably Brazil, Lake Superior, and India). Collector tips: look for smooth, water-worn surfaces that reveal interior colors.
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