sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture, variable colors including gray, orange, brown, and white, specific gravity of 2.58 to 2.64.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture, variable colors including gray, orange, brown, and white, specific gravity of 2.58 to 2.64.
Formation & geological history
Formed mainly within cavities of volcanic and metamorphic rocks through the deposition of silica-rich groundwater solutions in concentric layers over millions of years.
Uses & applications
Used in ornamental objects, jewelry, carvings, and precision instruments like mortars and pestles.
Geological facts
Agate is one of the most popular and varied gemstones, often found in ancient riverbeds and volcanic regions worldwide. The banding represents different stages of mineral deposition.
Field identification & locations
Can be identified in the field by its waxy luster, microcrystalline banding patterns, and hardness that easily scratches glass. Commonly found in gravel beds, glacial till, and volcanic areas.
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