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, and specific gravity of 2.58-2.64.
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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, and specific gravity of 2.58-2.64.
Formation & geological history
Formed mainly within cavities of volcanic and metamorphic rocks through the slow deposition of silica-rich groundwater over millions of years.
Uses & applications
Used in ornamental objects, jewelry, lapidary art, and precision instruments like mortar and pestles.
Geological facts
Agates are often found in ancient lava flows where gas bubbles were filled with silica-rich solutions, creating distinctive concentric bands.
Field identification & locations
Easily identified by its smooth, water-worn exterior and translucent banded or mottled interior when chipped or polished; commonly found in gravel beds, riverbeds, and volcanic regions worldwide.
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