sedimentary
Agate
Silicon dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, microscopic fibrous quartz structure, specific gravity of 2.58 to 2.64, commonly exhibits banded coloration.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, microscopic fibrous quartz structure, specific gravity of 2.58 to 2.64, commonly exhibits banded coloration.
Formation & geological history
Formed mainly in cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions over millions of years.
Uses & applications
Used in ornamental objects, jewelry, carving, making mortars and pestles, and as collector specimens.
Geological facts
Agate was named by Theophrastus, a Greek philosopher and naturalist, who discovered the stone along the shoreline of the Achates River in Sicily.
Field identification & locations
Easily identified by its characteristic concentric bands or layers of different colors. Found worldwide in volcanic rock cavities, particularly in Brazil, Uruguay, and the USA.
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