sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness: 6.5-7 on the Mohs scale, Color: Various shades of purple, pink, white, and red, Luster: Vitreous to waxy, Crystal Structure: Trigonal/Microcrystalline quartz, Cleavage: None, Specific Gravity: 2.58-2.64
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 on the Mohs scale, Color: Various shades of purple, pink, white, and red, Luster: Vitreous to waxy, Crystal Structure: Trigonal/Microcrystalline quartz, Cleavage: None, Specific Gravity: 2.58-2.64
Formation & geological history
Formed by the deposition of silica from groundwater, typically in cavities of igneous rocks such as basalt, over millions of years.
Uses & applications
Used primarily in jewelry, ornamental carvings, polished specimens, and collection displays.
Geological facts
Agate is a variety of chalcedony that often forms with distinctive concentric banding. The purple coloration in this specimen is typical of grape agate or dyed chalcedony varieties.
Field identification & locations
Easily identified by its waxy luster, hardness that scratches glass, and smooth tumbled surface. Found globally, notably in Brazil, India, Madagascar, and the United States.
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