sedimentary
Geode
Quartz / Chalcedony variety
AI-generated identification · may be incorrectHardness 7 on the Mohs scale, vitreous to dull luster, cryptocrystalline and microcrystalline structure, conchoidal fracture with no cleavage.
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Physical properties
Hardness 7 on the Mohs scale, vitreous to dull luster, cryptocrystalline and microcrystalline structure, conchoidal fracture with no cleavage.
Formation & geological history
Formed in hollow cavities of sedimentary or volcanic rocks through the slow deposition of silica-rich groundwater over millions of years.
Uses & applications
Popular as mineral specimens, decorative display items, and in lapidary arts for jewelry making.
Geological facts
Geodes often contain stunning crystal formations of amethyst, calcite, or quartz inside a nondescript outer rock shell.
Field identification & locations
Found worldwide in limestone formations and volcanic ash beds; easily identified by cracking open rounded, bumpy nodules.
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