Where is Geode found?
Chalcedony with Quartz crystals
Got a photo? Identify rocks instantly with the Rockby app
Open the appGeode occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Geode
Keokuk Geode Beds, Iowa, USA
Famous for large, high-quality geodes found in Mississippian-age limestones and shales. These geodes often contain quartz, calcite, dolomite, and sometimes pyrite or sphalerite.
Brazil
Known for producing massive amethyst geodes, particularly from the state of Rio Grande do Sul, found in basaltic lava flows.
Mexico
Significant source of amethyst and clear quartz geodes, often found in volcanic terrains.
Oregon, USA
Famous for 'thunder eggs,' which are a type of geode found in rhyolitic lava flows, often containing agate, jasper, and opal in addition to quartz.
Germany
Idar-Oberstein region is historically known for agate and quartz geodes, often found in volcanic rocks.
Collecting tips
- Look for spherical or ovoid shapes. Geodes often have a distinct rounded or irregular shape that stands out from the surrounding host rock. They may have a bumpy or cauliflower-like exterior.
- Check for a hollow sound. When tapped gently with a hammer, a geode may produce a hollow sound, indicating an internal cavity. This is not always reliable, as some geodes are solid or nearly solid.
- Examine weathered outcrops. Geodes are often more resistant to weathering than the surrounding host rock, causing them to erode out and be found loose on the surface or partially exposed in stream beds and road cuts.
- Identify host rock types. Focus your search in areas known for sedimentary rocks like limestone or shale, or volcanic rocks like basalt and rhyolite, which are common geode-forming environments.
- Look for 'rattlers'. Some geodes contain loose crystals or mineral fragments inside, which can be heard rattling when shaken. These are often highly prized.
Quick Check
- Color:
- Dull exterior, crystalline interior (often clear, white, or purple)
- Luster:
- Dull to earthy exterior, vitreous interior
- Streak:
- White (for quartz and chalcedony)
Explore Geode
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.