sedimentary
Banded Agate (specifically Eye Agate)
Chalcedony (Silicon Dioxide, SiO2)
Hardness: 6.5-7 Mohs; Color: White to creamy translucent with yellow/brown concentric circular bands; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Specific Gravity: 2.58-2.64.
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 Mohs; Color: White to creamy translucent with yellow/brown concentric circular bands; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Specific Gravity: 2.58-2.64.
Formation & geological history
Formed through the deposition of silica from groundwater in the cavities of igneous rocks or sedimentary veins. The 'eye' patterns are formed by rhythmic crystallization around a single point.
Uses & applications
Polished for use in jewelry, lapidary art, collection, and as worry stones or decorative accents.
Geological facts
Agate was named by Theophrastus, a Greek philosopher, who discovered the stone along the shore of the Achates River in Sicily. 'Eye' agates are highly sought after by collectors for their unique concentric patterns.
Field identification & locations
Identify by its waxy luster, translucency, and the presence of concentric banding (eyes). Commonly found in riverbeds, volcanic deposits, and beaches in Brazil, India, and the United States (Lake Superior region).
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