sedimentary
Agate Geode
Silicon Dioxide (SiO2) - Chalcedony variety
Hardness of 6.5 to 7 on the Mohs scale, exhibits concentric banding in various colors including white, grey, brown, and blue, waxy to vitreous luster, cryptocrystalline structure, no cleavage, specific gravity of 2.58 to 2.64
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, exhibits concentric banding in various colors including white, grey, brown, and blue, waxy to vitreous luster, cryptocrystalline structure, no cleavage, specific gravity of 2.58 to 2.64
Formation & geological history
Formed in cavities of sedimentary or volcanic rocks where silica-rich groundwater deposits microcrystalline quartz in layers over millions of years
Uses & applications
Used for ornamental objects, polished display specimens, jewelry, and lapidary art
Geological facts
Geodes start as gas bubbles in volcanic rock or animal burrows in sedimentary rock, which slowly fill with mineral-rich water precipitating crystals inward
Field identification & locations
Identified by its outer rind and hollow or crystal-filled interior with concentric banding, commonly found in regions with volcanic activity or limestone deposits globally
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