sedimentary
Agate
Chalcedony (SiO2)
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, various colors often showing concentric banding, specific gravity of 2.60 to 2.65.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, various colors often showing concentric banding, specific gravity of 2.60 to 2.65.
Formation & geological history
Formed mainly from deposition of silica from groundwater in the cavities of igneous, sedimentary, or metamorphic rocks over millions of years.
Uses & applications
Used widely in ornamental objects, jewelry, carving, and sometimes in precision instruments due to its hardness and durability.
Geological facts
Agate has been used since ancient times for decorative items and seals, and it is frequently associated with volcanic rock cavities where hydrothermal fluids deposit silica layers.
Field identification & locations
Identified by its waxy luster, conchoidal fracture, and distinct banded patterns, commonly found in riverbeds, gravel deposits, and volcanic regions worldwide.
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