sedimentary
Geode (Unopened)
Crystalline Quartz or Chalcedony filled Geode (SiO2)
Hardness: 7 (Mohs scale), Color: Brownish or grey exterior with white or tan hints, Luster: Dull or earthy on exterior, Crystal Structure: Hexagonal (interior), Cleavage: None, Specific Gravity: 2.60-2.65
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: Brownish or grey exterior with white or tan hints, Luster: Dull or earthy on exterior, Crystal Structure: Hexagonal (interior), Cleavage: None, Specific Gravity: 2.60-2.65
Formation & geological history
Formed in sedimentary rock cavities (such as limestone) through mineral precipitation from groundwater over millions of years. Common in Mississippian and Devonian strata.
Uses & applications
Geological collecting, lapidary arts, metaphysical/decorative purposes, and educational specimens.
Geological facts
Geodes look like ordinary round rocks on the outside but contain hollow centers filled with crystals. The word 'geode' comes from the Greek word 'geoides' meaning earth-like.
Field identification & locations
Identify by its unusually light weight relative to its size and rounded, bumpy, cauliflower-like exterior. Common in the Midwest USA (Keokuk region) and Brazil.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary