Geode
From Wikipedia, the free encyclopedia.
Two geodes, halved and polished.
are geological formations common to the
United States (
Indiana, the
Keokuk area of
Iowa and
Kentucky),
Brazil and
Mexico. Essentially rock bubbles with internal cystal formations, the exterior of a geode is generally limestone or a related rock, while the interior contains
quartz crystals and/or
chalcedony deposits. Geodes work their way up to the surface of the earth crust's after millions of years.
Geologists do not yet have a widely accepted theory about how geodes are formed.
