mineral
Agate Geode
Silicon dioxide (SiO2) - Chalcedony
AI-generated identification · may be incorrectHardness: 6.5-7 on the Mohs scale. Color: Banded white/tan/gray interior with a dark green or gray exterior rind. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on the Mohs scale. Color: Banded white/tan/gray interior with a dark green or gray exterior rind. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed by the deposition of silica from groundwater in cavities (vesicles) within igneous volcanic rocks, such as basalt. The mineral layers precipitate out over thousands of years.
Uses & applications
Decorative purposes, crystal healing collections, jewelry (cabochons), and lapidary art.
Geological facts
The word 'agate' comes from the Achates River in Sicily, where the mineral was first found by the Greek philosopher Theophrastus around 300 BC.
Field identification & locations
Identify by its characteristic banding, translucent interior, and rough, dull exterior 'skin'. Commonly found in volcanic regions of Brazil, Uruguay, and the United States (western states).
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