mineral
Banded Agate
Chalcedony (Cryptocrystalline Silica) SiO2
Hardness: 6.5-7 (Mohs), Color: Tan, brown, and cream concentric bands, Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline), Cleavage: None, Specific Gravity: 2.58-2.64
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Tan, brown, and cream concentric bands, Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline), Cleavage: None, Specific Gravity: 2.58-2.64
Formation & geological history
Formed in cavities of volcanic rocks or ancient lavas through the deposition of silica from groundwater. The bands represent different stages of mineral precipitation over thousands of years. Usually date back to the Cenozoic or Mesozoic eras.
Uses & applications
Used primarily in jewelry (beads, cabochons), lapidary arts, decorative carvings, and as collectible specimens. Due to its hardness, it is also used in precision mortars and pestles.
Geological facts
The name 'agate' comes from the Achates River in Sicily, where agates were first discovered. No two agates are exactly alike, making each specimen unique to collectors.
Field identification & locations
Identified by its characteristic concentric 'fortification' banding and waxy texture. Commonly found in riverbeds, lake shores (like Lake Superior), and volcanic regions. It is translucent when held up to a strong light source.
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