gemstone
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness: 6.5-7 on Mohs scale; Color: Variable, often banded in grey, white, blue, brown, or red; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None; Specific gravity: 2.58-2.64
- Hardness
- 6
- Color
- Variable, often banded in grey, white, blue, brown, or red
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Variable, often banded in grey, white, blue, brown, or red; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None; Specific gravity: 2.58-2.64
Formation & geological history
Formed mainly in cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions over millions of years.
Uses & applications
Used in jewelry, decorative items, ornaments, and historically for precision instruments and mortars.
Geological facts
Agates are known for their distinct concentric banding patterns formed by the rhythmic deposition of silica. The name comes from the Achates River in Sicily where they were found in antiquity.
Field identification & locations
Identified by its waxy luster, conchoidal fracture, and characteristic banding. Found worldwide, particularly in Brazil, India, Germany, and the United States.
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