sedimentary
Quartz Geode
Silicon Dioxide (SiO2)
Hardness of 7 on the Mohs scale, typically white or translucent color, vitreous to sugary luster, trigonal crystal system, conchoidal fracture with no true cleavage, specific gravity of 2.65.
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Physical properties
Hardness of 7 on the Mohs scale, typically white or translucent color, vitreous to sugary luster, trigonal crystal system, conchoidal fracture with no true cleavage, specific gravity of 2.65.
Formation & geological history
Formed in cavities of sedimentary or volcanic rocks where silica-rich groundwater percolated through, slowly depositing microcrystalline and crystalline quartz layers over millions of years.
Uses & applications
Commonly collected as mineral specimens, used in decorative items, lapidary arts, and sometimes in jewelry.
Geological facts
Geodes form when hollow bubbles in rock (such as from gas in volcanic rock or animal burrows in limestone) are slowly filled with mineral-rich water over immense spans of time.
Field identification & locations
Easily identified by its rough, nodular exterior combined with a hollow interior lined with sparkling quartz crystals. Found worldwide, with notable deposits in Brazil, Mexico, and the United States (such as in Indiana, Iowa, and Kentucky).
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Banded Siltstone / Mudstone Pebble
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