sedimentary

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale; Color: White to translucent crystals on brown host rock; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture).

Hardness: 7 on Mohs scale
Color: White to translucent crystals on brown host rock
Luster: Vitreous (glassy)

Identified April 25, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: White to translucent crystals on brown host rock; Luster: Vitreous (glassy); Crystal Structure: Hexagonal/Trigonal; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed as secondary mineral growth within hollow cavities of sedimentary or volcanic rocks. Mineral-rich groundwater seeps into voids, precipitating silica over millions of years.

Uses & applications

Primarily used for geological education, home decor, and metaphysical collections. Industrial quartz is used in electronics and glassmaking.

Geological facts

The word geode comes from the Greek word 'Geoides' meaning earth-like. Unlike a solid nodule, a true geode must have a hollow interior, though fragments like this represent the crystal wall.

Field identification & locations

Identify in the field by looking for rounded, bumpy 'nodules' that feel lighter than they look. Found commonly in limestone or shale beds in states like Iowa, Indiana, or in desert regions.