sedimentary
Quartz Geode
Silicon Dioxide (SiO2)
Hardness of 7 on Mohs scale. Dull, bumpy exterior with internal crystalline quartz pockets. Color ranges from tan and grey exterior to clear/white or brownish interior quartz crystals. Conchoidal fracture, glassy to dull luster.
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Physical properties
Hardness of 7 on Mohs scale. Dull, bumpy exterior with internal crystalline quartz pockets. Color ranges from tan and grey exterior to clear/white or brownish interior quartz crystals. Conchoidal fracture, glassy to dull luster.
Formation & geological history
Formed by chemical precipitation from hydrothermal fluids or groundwater within spherical cavities in volcanic or sedimentary rocks over thousands to millions of years.
Uses & applications
Popular for lapidary work, gemstone collections, educational specimens, ornamental display pieces, and metaphysical practices.
Geological facts
Geodes look like ordinary, rounded rocks from the outside, but when cracked open, they reveal hollow interiors lined with sparkling quartz crystals or agate bands.
Field identification & locations
Look for rounded, nodular rocks that feel unusually lightweight for their size, often found in limestone formations, volcanic ash beds, or stream beds in geode-rich regions like Iowa, Missouri, and Indiana.
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