sedimentary
Banded Agate
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Brown, white, and black concentric bands; Luster: Waxy to vitreous; Structure: Trigonal/Microcrystalline; Cleavage: None; Fracture: Conchoidal.
- Hardness
- 6
- Color
- Brown, white, and black concentric bands
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, white, and black concentric bands; Luster: Waxy to vitreous; Structure: Trigonal/Microcrystalline; Cleavage: None; Fracture: Conchoidal.
Formation & geological history
Formed in cavities within volcanic or sedimentary rocks through the deposition of silica from groundwater over thousands to millions of years.
Uses & applications
Commonly used in jewelry, ornamental carvings, lapidary arts, and as lucky charms or pocket stones.
Geological facts
Agate is often named after the Achates River in Sicily where it was first discovered. The banding found in these stones is caused by varying impurities in the silica layers.
Field identification & locations
Identified by its distinctive concentric banding and translucency. Commonly found in riverbeds, gravel deposits, and volcanic regions globally (notably Brazil, Uruguay, and Lake Superior).
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