sedimentary
Geode (Unopened)
Quartz/Chalcedony concretion
Rough, bumpy exterior, typically spherical or subspherical, hardness of 7 (if quartz/chalcedony based), dull exterior luster until opened.
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Physical properties
Rough, bumpy exterior, typically spherical or subspherical, hardness of 7 (if quartz/chalcedony based), dull exterior luster until opened.
Formation & geological history
Formed in sedimentary or igneous rocks where mineral-rich water seeps into cavities and deposits crystals over time.
Uses & applications
Collected by rockhounds, often cut or cracked open to reveal internal crystals for display or jewelry.
Geological facts
Geodes can contain a variety of minerals inside, most commonly quartz, amethyst, or calcite.
Field identification & locations
Identified by their round, lumpy shape, lighter weight than expected (if hollow), and rattling sound if loose crystals are inside. Commonly found in areas with limestone or volcanic ash beds.
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