sedimentary
Agate Geode
Silicon Dioxide (Chalcedony / Quartz), SiO2
Hardness of 6.5 to 7 on the Mohs scale, waxy to vitreous luster, cryptocrystalline crystal structure, conchoidal fracture, and specific gravity of 2.6 to 2.7.
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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 2.6 to 2.7.
Formation & geological history
Formed in cavities in volcanic and sedimentary rocks where silica-rich groundwater deposits microcrystalline quartz in concentric layers over millions of years.
Uses & applications
Commonly used in jewelry, ornamental carvings, lapidary art, and geological specimen collecting.
Geological facts
Geodes appear as ordinary rocks on the outside, but cracking them open reveals a stunning hollow cavity lined with brilliant crystals or colorful banded agate.
Field identification & locations
Easily identified by its exterior bumpy texture and interior banded patterns or crystal linings. Found worldwide, particularly in Brazil, Uruguay, Mexico, and the USA.
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