print email comment close Geodes: Small Treasure Vaults in Illinois URL: http://www.isgs.uiuc.edu/maps-data-pub/publications/geobits/geobit3.shtml Description: Illustrated fact sheet about these irregular, roughly spherical geological formations that are lined with mineral crystals. Describes the makeup of a geode and theories about geode formation. From the Illinois State Geological Survey. Publisher: Illinois State Geological Survey LII Database Information: Record 23749 created by Jennifer English on 04/30/2007 Last modification on 06/12/2007 Published: 05/03/2007   Funding agency: California State Library LII Item ID: http://lii.org/cs/lii/view/item/23749