sedimentary
Agate
Silicon dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with no true cleavage, specific gravity of 2.58 to 2.64, often exhibits distinct concentric banding or patterns of various colors.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with no true cleavage, specific gravity of 2.58 to 2.64, often exhibits distinct concentric banding or patterns of various colors.
Formation & geological history
Formed primarily within the cavities of volcanic and metamorphic rocks through the deposition of silica-rich groundwater solutions over long periods.
Uses & applications
Used widely in ornamental carvings, jewelry, lapidary art, polished specimens, and precision instruments like mortar and pestles.
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 in the field by its waxy luster, smooth water-worn surface, and characteristic translucent banding when held to the light. Found worldwide, particularly in Brazil, Uruguay, India, Madagascar, and the United States.
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