sedimentary
Agate
Silicon dioxide (Chalcedony), SiO2
Hardness: 6.5-7 on the Mohs scale; Color: Multicolored with bands of white, grey, red, orange, and brown; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on the Mohs scale; Color: Multicolored with bands of white, grey, red, orange, and brown; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline quartz); Cleavage: None
Formation & geological history
Formed by the deposition of silica from groundwater in the cavities of igneous and sedimentary rocks, typically over millions of years.
Uses & applications
Used primarily in jewelry, ornamental carvings, polished specimens for display, and precision instruments like mortar and pestles.
Geological facts
Agate was named by Theophrastus, a Greek philosopher, who discovered the stone along the shoreline of the Achates river in Sicily.
Field identification & locations
Easily identified by its distinctive concentric banding and waxy luster. Commonly found worldwide, especially in volcanic rock cavities.
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