The area around Keokuk, Iowa is sometimes referred to as “the geode capital of the world. Geodes have been collected from the Lower Warsaw Formation within about 100 miles of the city for over 150 years. Keokuk geodes contain a variety of minerals, but quartz is dominant in most. Calcite is also a common mineral in many geodes though 17 other minerals have been identified in Keokuk Geodes including pyrite and sphalerite.
Unlike most geodes that form in volcanic rock, Keokuk geodes are found in the sedimentary rock. They started out as concretions, balls of mud, which formed around organic material about 340 million years ago. The outer shells of these concretions were subsequently replaced by chalcedony and the interiors of the concretions were dissolved, leaving a hollow space into which quartz crystals could grow.
How big are Keokuk Geodes?
Most geodes are 2 to 5 inches wide, though specimens as large as two feet across have been found.
What minerals are inside Keokuk Geodes?
Keokuk geodes contain a variety of minerals, but quartz is dominant in most. Many geodes are filled with clear to white quartz crystals. Micro-crystalline quartz, or chalcedony, whose component crystals are too small to be seen with the naked eye, forms the outer shell. Chalcedony layers also encrust the interior walls of many geode cavities, covering the surfaces of the earlier-generation quartz crystals in a variety of colors, including white, gray, blue, yellow and orange. Calcite is also a common mineral in many geodes though 17 other minerals have been identified in Keokuk Geodes including pyrite and sphalerite.
Where are Keokuk Geodes found?
Keokuk Geodes are collected from the Lower Warsaw Formation within about 100 miles of the city of Keokuk. There are over 300 known geode containing exposures. The main exposures are found in stream beds that are tributaries of the Mississippi River. Many geodes are found loose in the creek beds, having weathered out of the rock and been transported downstream.
Christmas is rapidly approaching. For US customers there is still time to place orders and have them arrive in time for x-mas. For International customers only expensive, expedited shipping methods will be able to get them there in time.
While we are continuing to get most orders shipped out within 1-2 business days we CANNOT guarantee any delivery times. Delivery delays are very common this time of year as shipping volumes increase. We have no control over these delays.
The dates below are the cutoffs based on carrier provided transit times.
UPS Ground: Friday, Dec 14th
USPS First Class: Tuesday, Dec 18th
USPS Priority: Wednesday, Dec 19th
UPSP Priority Express: Thursday, Dec 20th
These are based on all US locations, it may be possible to receive shipments faster to areas of the country closer to are warehouse. Please contact us if you have any questions.