sedimentary

Quartz Geode Fragment

Silicon Dioxide (SiO2)

Hardness: 7 Mohs; Color: Tan/grey exterior, clear to white interior; Luster: Vitreous (glassy) inside, earthy outside; Crystal Structure: Hexagonal (inside cavity); Cleavage: None/Conchoidal.

Hardness: 7 Mohs
Color: Tan/grey exterior, clear to white interior
Luster: Vitreous (glassy) inside, earthy outside

Identified July 20, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Tan/grey exterior, clear to white interior; Luster: Vitreous (glassy) inside, earthy outside; Crystal Structure: Hexagonal (inside cavity); Cleavage: None/Conchoidal.

Formation & geological history

Formed in sedimentary rock cavities (like limestone) by the slow deposition of mineral-rich water over millions of years, typically during the Mississippian period. The exterior is often a hard chalcedony shell.

Uses & applications

Primarily used for educational displays, home decor, and as entry-level specimens for amateur collectors.

Geological facts

The word geode comes from the Greek word 'Geoides' which means 'earth-like'. Despite their plain exterior, they hide beautiful crystalline interiors. This specimen appears to be a small, weathered fragment or a whole mini-nodule.

Field identification & locations

Identify by looking for a rounded shape with a distinct 'shell' and possible crystal sparkle in hollow areas. Common in states like Iowa (Keokuk) and Indiana in the US. Collectors often shake them to hear if loose crystals rattle inside.