sedimentary

Geode

Quartz nodule with chalcedony and crystalline interior

AI-generated identification · may be incorrect

Hardness of 7 on the Mohs scale for the quartz crystals, with a vitreous to dull luster and conchoidal fracture. Exterior is typically rough, bumpy limestone or basalt, while the hollow interior contains quartz or calcite crystal linings.

Identified October 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in sedimentary or volcanic rock cavities where mineral-rich groundwater slowly precipitates silica or other minerals over millions of years. Common in limestone formations and volcanic ash beds.

Uses & applications

Popular as mineral specimens, decorative items, and in lapidary arts for jewelry making when sliced open.

Geological facts

Geodes start as hollow bubbles in rock, such as gas bubbles in lava or animal burrows in mud, which slowly fill inward without becoming solid.

Field identification & locations

Identified by their rounded, often spherical shape with a bumpy exterior, feeling unusually lightweight for their size due to the hollow interior. Commonly found in regions like the midwestern United States, Mexico, and Brazil.