sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5-7 on the Mohs scale, colors range widely including brown, red, grey, and white, waxy to vitreous luster, microcrystalline crystal structure, conchoidal fracture, specific gravity of 2.58-2.64.
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Physical properties
Hardness of 6.5-7 on the Mohs scale, colors range widely including brown, red, grey, and white, waxy to vitreous luster, microcrystalline crystal structure, conchoidal fracture, specific gravity of 2.58-2.64.
Formation & geological history
Formed mainly by the deposition of silica from groundwater in the cavities of igneous, metamorphic, or sedimentary rocks. Geological age varies greatly from Precambrian to Cenozoic.
Uses & applications
Used in ornamental objects, jewelry, and lapidary arts, as well as industrial bearings and mortars due to its hardness.
Geological facts
Agates are a form of chalcedony quartz and often display distinct concentric banding formed as mineral-rich fluids deposited layers over time inside cavities.
Field identification & locations
Found worldwide in volcanic rock cavities or weathered river gravels. Identified by its waxy luster, hardness, and banded or mottled patterns.
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