sedimentary
Agate
Silicon dioxide (chalcedony variety), SiO2
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, colors range from white, gray, blue, green, red, to brown, conchoidal fracture, specific gravity of 2.58-2.64.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, colors range from white, gray, blue, green, red, to brown, conchoidal fracture, specific gravity of 2.58-2.64.
Formation & geological history
Formed mainly in cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions, often in concentric bands over millions of years.
Uses & applications
Used for ornamental objects, jewelry, tumbled stones, carvings, and precision instruments.
Geological facts
Agates are named after the Achates River in Sicily where they were found in ancient times. They often preserve fascinating banding patterns reflecting changes in mineral content during formation.
Field identification & locations
Easily identified by its distinctive concentric banding, waxy luster, and resistance to scratching by steel. Found worldwide, particularly in Brazil, USA, Uruguay, and India.
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