sedimentary
Agate
Silicon dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, variable colors showing concentric banding or patterns, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity of 2.58 to 2.64.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, variable colors showing concentric banding or patterns, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, specific gravity of 2.58 to 2.64.
Formation & geological history
Formed mainly in cavities of volcanic and metamorphic rocks through the slow deposition of silica-rich groundwater solutions over millions of years.
Uses & applications
Used in ornamental objects, jewelry, carvings, and precision instruments like mortar and pestles due to its hardness.
Geological facts
Agate was named by the Greek philosopher Theophrastus after the Achates river in Sicily where stones were found in antiquity.
Field identification & locations
Identified by its characteristic banding, translucent edges, and waxy luster. Common worldwide, especially in Brazil, Uruguay, and parts of the United States like Lake Superior.
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