mineral
Agate
Banded Chalcedony (SiO2)
AI-generated identification · may be incorrectHardness: 6.5–7 (Mohs scale); Color: Variegated bands of brown, white, and grey; Luster: Waxy to vitreous when polished; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58–2.64
- Hardness
- 6
- Color
- Variegated bands of brown, white, and grey
- Luster
- Waxy to vitreous when polished
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Variegated bands of brown, white, and grey; Luster: Waxy to vitreous when polished; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.58–2.64
Formation & geological history
Formed by the deposition of silica from groundwater in the cavities (vesicles) of igneous rocks or in sedimentary pockets. These layers form rhythmically over time.
Uses & applications
Used primarily in jewelry (cabochons), ornamental carvings, burnishing tools for metalworking, and as precision bearings in laboratory balances.
Geological facts
Ancient Greeks and Romans used agates for signet rings and amulets; the stone gets its name from the Achates River in Sicily where it was famously found in antiquity.
Field identification & locations
Identify by distinctive banding patterns and translucency. Commonly found in basaltic lava flows and gravel beds. Collectors look for unique 'eye' or 'fortification' patterns.
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