sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness: 6.5-7 on the Mohs scale; Color: Varied, including white, gray, blue, red, green, and brown; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None; Specific gravity: 2.58-2.64
- Hardness
- 6
- Color
- Varied, including white, gray, blue, red, green, and brown
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on the Mohs scale; Color: Varied, including white, gray, blue, red, green, and brown; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None; Specific gravity: 2.58-2.64
Formation & geological history
Formed primarily within cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions in rhythmic bands over geological time.
Uses & applications
Used in ornamental objects, jewelry, carving, and as a collector's specimen.
Geological facts
Agate is named after the Achates River in Sicily, where stones were found in ancient times. It has been used for seals, signet rings, and ornamentation since ancient civilizations.
Field identification & locations
Identified by its distinctive banding patterns, waxy luster, and conchoidal fracture. Commonly found in regions with ancient volcanic activity worldwide.
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