sedimentary

Geode

Quartz nodule / Chalcedony-lined cavity

AI-generated identification · may be incorrect

Hardness of 7 on the Mohs scale (for the quartz interior), varies in color from white, grey, brown to translucent, dull outer crust with vitreous or sparkly interior crystals, cryptocrystalline to microcrystalline structure, no distinct cleavage.

Identified August 4, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in sedimentary or volcanic rocks where groundwater dissolves cavity minerals and deposits silica over millions of years.

Uses & applications

Commonly collected as lapidary specimens, used in decorative items and jewelry making.

Geological facts

Geodes often start as hollow bubbles in volcanic rock or animal burrows in sedimentary rock, gradually filling with mineral-rich water.

Field identification & locations

Found worldwide in limestone formations, volcanic ash beds, and deserts; often identified by their rounded, knobby exterior and hollow, crystal-lined interior when cracked open.