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Thursday, August 6, 2009

Geodes rare in Ohio

Ohio is not known for geodes. Almost all of the geodes reported are calcite geodes reported in limestones and dolomites from southwestern Ohio. Geodes are rare but limestones and dolomites are almost devoid of voids and are only created by geodizing fossil remains and concentrations.

Joseph W. Vasichko wrote an excellent article about geodized brachiopods from near Georgetown Ohio. I have collected very similar material at Hueston Woods State park near Oxford Ohio

Drusy Quartz geodes have been reported near Portsmouth Ohio. I have not visited this area nor can I find a well documented reference. Maybe I'll make an early autumn trip to check it out.

Petrified Wood can be found along the river near Barnesville Ohio. Some of petrified is highly siliceous and can small vugs of drusy quartz. (Not really a geode though).

There is a cave on put-in-bay south bass Island that has been listed by some as the world's largest geode (really a small cave).


The World's Largest Geode, Crystal Cave, South Bass Island, Put-in-Bay, Ohio


Geodes are rock formations that occur in sedimentary and certain volcanic rocks. They are basically cavities with internal crystal formations. Crystal Cave is the world's largest geode. Discovered in 1887 as workers for the winery were digging a well, the cave is located about 40 feet below the surface. The crystals have a blueish color and are made of strontium sulfate (SrSO4). The geode is 35 feet in diameter at its widest point and some of the crystals that measure as wide as 18 inches across and weighing up to 300 lbs. The present geode is smaller than it was when it was originally discovered because some of the crystals were harvested and sold for the manufacturing of fireworks.

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