sedimentary
Geode (Unopened)
Silicon dioxide with various inclusions (SiO2)
Hardness: 7 (Quartz shell), Color: Dull tan or gray exterior with possible iron staining, Luster: Earthy exterior, Crystal structure: Hidden (likely microcrystalline or macrocrystalline inside), Specific Gravity: 2.6-2.7
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Quartz shell), Color: Dull tan or gray exterior with possible iron staining, Luster: Earthy exterior, Crystal structure: Hidden (likely microcrystalline or macrocrystalline inside), Specific Gravity: 2.6-2.7
Formation & geological history
Formed in sedimentary environments like limestone or volcanic ash beds through chemical precipitation of minerals into gas bubbles or animal burrows. They can be hundreds of millions of years old.
Uses & applications
Primarily for mineral collecting, lapidary arts, education, and decorative interior design.
Geological facts
Geodes are like nature's 'surprise eggs'; you cannot be certain of the mineral growth inside until they are cracked open. The word geode comes from the Greek word 'Geoides' meaning earth-like.
Field identification & locations
Look for rounded, bumpy, or 'cauliflower-like' outward appearances that feel unusually light for their size. Common in Iowa, Indiana, Mexico, and Brazil. Shake them to check for loose crystals (rattlers).
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary