sedimentary
Agate
Silicon Dioxide (SiO2) - Chalcedony variety
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, and specific gravity of 2.58 to 2.64. Colors vary widely including white, grey, blue, red, orange, and brown, often exhibiting banded patterns.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture, and specific gravity of 2.58 to 2.64. Colors vary widely including white, grey, blue, red, orange, and brown, often exhibiting banded patterns.
Formation & geological history
Formed primarily within cavities of volcanic and metamorphic rocks through the deposition of silica from groundwater solutions, typically in rhythmic layers over geological time.
Uses & applications
Commonly used in ornamental objects, jewelry, tumbled stones, leather burnishing tools, and precision instrument bearings.
Geological facts
Agates are among the most popular stones for lapidary work. The name comes from the Achates River in Sicily, where agates were found in antiquity.
Field identification & locations
Identified easily by its waxy luster, conchoidal fracture, and often distinct banding. Found globally, notably in Brazil, Uruguay, the USA (such as Lake Superior agates), and India.
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