mineral
Banded Agate (with Quartz Geode Center)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 (Mohs); Color: Gray, white, and translucent; Luster: Vitreous to waxy; Crystal structure: Hexagonal (Trigonal); Cleavage: None; SG: 2.58–2.64.
- Hardness
- 6
- Color
- Gray, white, and translucent
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Gray, white, and translucent; Luster: Vitreous to waxy; Crystal structure: Hexagonal (Trigonal); Cleavage: None; SG: 2.58–2.64.
Formation & geological history
Formed in volcanic rock cavities or ancient sedimentary rocks. Silica-rich groundwater deposits layers of chalcedony over time, often ending with macro-crystalline quartz centers. Most date back to the Cretaceous or Tertiary periods.
Uses & applications
Primarily used for lapidary arts, jewelry, carvings, and as decorative metaphysical specimens or paperweights.
Geological facts
The distinctive banding is caused by rhythmic crystallization cycles. This specific specimen is a 'polished point' or 'tower' which has been cut and polished to highlight the interior banding.
Field identification & locations
Identify in the field by its waxy luster and concentric banding when broken or cut. Common in Brazil, Uruguay, and the Lake Superior region of the USA.
