🪨 Geode facts
| Age | Mississippian, about 340 million years old (Warsaw Formation) |
|---|---|
| Origin & sources | Within about 70 miles of Keokuk, Iowa, where Iowa, Missouri and Illinois meet. It is Iowa's state rock. |
| Composition | Chalcedony shell with quartz, often calcite, dolomite, pyrite, sphalerite or kaolinite |
How it forms
Nodules formed in shallow-sea mud and limestone. Their cores later dissolved and refilled with crystals, giving some of the most varied geode interiors in the world.
Mineral data: see Quartz.
🌍 Where it's found
- Type locality
- Notable source / deposit
- Country of origin
Marker positions are approximate (region or locality level). Type localities from Wikidata; notable sources curated by Crystopedia.
Learn more
Geode / nodule
Orange
RootCrown
Healing crystal
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