sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, colors range from red, brown, and white to gray and black, vitreous to waxy luster, cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.58-2.64
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, colors range from red, brown, and white to gray and black, vitreous to waxy luster, cryptocrystalline crystal structure, conchoidal fracture with no true cleavage, specific gravity of 2.58-2.64
Formation & geological history
Formed primarily within the 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, decorative carvings, precision instruments, and lapidary collecting
Geological facts
Agates are often found in ancient lava flows where gas bubbles left empty cavities that later filled with silica-rich fluids
Field identification & locations
Identifiable by its distinct banded patterns and waxy luster, commonly found in riverbeds, glacial tills, and volcanic regions worldwide
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