sedimentary
Quartz Geode
Silicon Dioxide (SiO2)
Hardness of 7 on the Mohs scale, typically yellowish to brown exterior due to weathering, vitreous to dull luster, cryptocrystalline or microcrystalline structure, conchoidal fracture.
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Physical properties
Hardness of 7 on the Mohs scale, typically yellowish to brown exterior due to weathering, vitreous to dull luster, cryptocrystalline or microcrystalline structure, conchoidal fracture.
Formation & geological history
Formed in cavities in sedimentary or volcanic rocks where silica-rich groundwater circulates and deposits minerals over millions of years.
Uses & applications
Used in decorative items, mineral collections, and lapidary work.
Geological facts
Geodes appear as ordinary, unassuming round rocks on the outside, but cracking them open reveals a sparkling interior lined with quartz crystals.
Field identification & locations
Found worldwide in limestone formations, volcanic ash beds, and deserts. Collectors often tap them with a hammer to reveal the crystal lining.
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