sedimentary
Banded Agate
Silicon dioxide (SiO2) - variety of Chalcedony
Hardness: 6.5-7 on Mohs scale; Color: Red, brown, tan, and white bands; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58-2.64
- Hardness
- 6
- Color
- Red, brown, tan, and white bands
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Red, brown, tan, and white bands; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58-2.64
Formation & geological history
Formed in cavities of volcanic rock or ancient sedimentary formations where silica-rich groundwater deposited layers over time. This tumbled specimen likely originated from river deposits.
Uses & applications
Used primarily for jewelry (beads, cabochons), home decor, meditation stones, and as a durable abrasive in industrial polishing lapidary work.
Geological facts
Agate is named after the Achates River in Sicily. Each agate is unique because the banding patterns are formed by localized mineral impurities and fluctuating pressure during slow mineral growth.
Field identification & locations
Identify by its characteristic banding, hardness (it can scratch glass), and waxy feel when polished. Commonly found in riverbeds, lakeshores, and volcanic outcrops globally.
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