sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, variable colors often in concentric bands, waxy to vitreous luster, microcrystalline crystal structure, conchoidal fracture with no true cleavage, and a specific gravity around 2.6 to 2.7.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, variable colors often in concentric bands, waxy to vitreous luster, microcrystalline crystal structure, conchoidal fracture with no true cleavage, and a specific gravity around 2.6 to 2.7.
Formation & geological history
Forms primarily within cavities of volcanic and metamorphic rocks through the slow deposition of silica-rich groundwater solutions over millions of years.
Uses & applications
Widely used in ornamental objects, jewelry, polished specimens, decorative carvings, and precision instruments like mortars and pestles due to its durability.
Geological facts
Agates were named by the ancient Greek philosopher Theophrastus after the Achates river in Sicily where the stones were initially found.
Field identification & locations
Identified by its distinct concentric banding, waxy luster, and translucent to opaque appearance. Commonly found globally in volcanic regions such as Brazil, India, and parts of the United States.
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