sedimentary
Geode
Quartz / Chalcedony nodule
AI-generated identification · may be incorrectMohs hardness of 7; vitreous to dull luster; crypto-crystalline structure; exhibits conchoidal fracture with no true cleavage.
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Physical properties
Mohs hardness of 7; vitreous to dull luster; crypto-crystalline structure; exhibits conchoidal fracture with no true cleavage.
Formation & geological history
Formed in hollows of sedimentary or volcanic rocks via groundwater mineral precipitation over millions of years.
Uses & applications
Commonly collected as mineral specimens, cut and polished for ornamental displays, and used in lapidary arts.
Geological facts
Geodes often feature inward-growing crystal linings of quartz, amethyst, or calcite inside a tough outer chalcedony shell.
Field identification & locations
Identify by a spherical, bumpy exterior and a hollow or crystal-filled interior when broken open; found globally in limestone formations.
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