sedimentary

Geode with Quartz Crystal Cavity

Silicon Dioxide (SiO2) in Calcareous/Siliceous Matrix

Hardness: 7 (crystals) / 3-5 (matrix). Color: Tan/brown exterior with white/clear crystals. Luster: Vitreous (crystals) to dull (exterior). Crystal structure: Trigonal (hexagonal prisms). Cleavage: None/Conchoidal.

Hardness: 7 (crystals) / 3-5 (matrix)
Color: Tan/brown exterior with white/clear crystals
Luster: Vitreous (crystals) to dull (exterior)

Identified April 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as hollow cavities in sedimentary rock layers, often by bubbles or dissolved organic material. Minerals precipitate from groundwater over millions of years (often Jurassic to Eocene ages) to line the cavity.

Uses & applications

Primarily used for geological education, tabletop decor, and as a popular item for amateur rock collectors and metaphysical stores.

Geological facts

Geodes appear to be ordinary rocks from the outside, but their hollow interiors can contain massive crystal formations. The name comes from the Greek word 'Geoides' meaning earth-like.

Field identification & locations

Identify by looking for rounded, lumpy, or 'cauliflower-like' textures on the exterior. Often lighter in weight than solid rocks of the same size. Commonly found in desert environments like Utah, Iowa, and Mexico.

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