sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, variable colors due to impurities, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, and a specific gravity around 2.60 to 2.65.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, variable colors due to impurities, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, and a specific gravity around 2.60 to 2.65.
Formation & geological history
Formed 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 for ornamental objects, jewelry, polished lapidary specimens, mortars and pestles for laboratory use, and sought after by mineral collectors.
Geological facts
Agate is one of the most popular stones used in lapidary arts due to its durability and striking banded patterns. It was named by the Greek philosopher Theophrastus after the Achates river in Sicily.
Field identification & locations
Identified by its distinctive banded patterns, waxy luster, and resistance to scratching by steel. Commonly found in riverbeds, volcanic regions, and gravel deposits worldwide.
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