sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture, and specific gravity of 2.58-2.64. Typically displays multicolored banding.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture, and specific gravity of 2.58-2.64. Typically displays multicolored banding.
Formation & geological history
Formed by the deposition of silica from groundwater in the cavities of igneous and sedimentary rocks, often developing over millions of years in concentric layers.
Uses & applications
Widely used in ornamental carvings, jewelry, tumbled stones, and occasionally in industrial applications due to its hardness.
Geological facts
Agates were highly valued in antiquity as amulets and for making seal rings and intaglios. The name comes from the Achates River in Sicily, where agates were found in ancient times.
Field identification & locations
Can be identified in the field by its waxy luster, distinct concentric banding patterns, and translucent edges when held up to light. Commonly found worldwide in volcanic rock cavities.
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