2007-02-28

geodes: what are they?

Geodes are natural inorganic objects which are hollow. Geodes are usually roughly spherical in shape and can occur in igneous or sedimentary rock. The interior may be lined with crystals, usually quartz, pointing toward the center. Quartz consists esentially of the elements silicon and oxygen, but exhibits many varieties of color and form. Geodes are sometimes lined with chalcedony, a variety of quartz and, on occasion, closely related opal.

The hollow interior of the geode is it's most characteristic feature. If the interior of a formation is completely filled in, it is then classified as a nodule, not a geode. Nodules can be composed of a number of minerals, such as agate, quartz or calcite.

Geodes usually occupy the sites of former gas cavities in the volcanic rocks, basalt, rhyollite and tuff. Geodes can also occur in various other environments, such as sedimentary rock, which occurs as shale formed by ancient oceans. The interiors of geodes are very different from their exteriors and until a geode is opened, there is no easy way to determine what is inside.

If you have additional information about geodes, unique or interesting ways to open them, or information on geode collecting sites, please leave a comment to this post.

21 comments:

Anonymous said...

Are there any sites close to memphis where I can look for geodes?

argon(one) said...

I have not found geodes in the Memphis area. Most of the geodes that I have collected in Tennessee have come from the Livingston area, northeast of Nashville, about five hours from Memphis. There are also geode locations in Kentucky, Indiana, Missouri and Iowa. Kiokuk, Iowa, south of St. Louis is a great place to collect geodes.

Anonymous said...

thanks

krikit said...

Do you know anything about rocks or minerals that could be found in Alberta Canada?

argon(one) said...

Hello krikit... for information about minerals in Alberta you can contact the Calgary Mineral Exploration Group Society by email at
info@meg.calgary.ab.ca

Anonymous said...

I have been finding geodes in Byrdstown, TN for years. Most of them have quartz crystal interiors, but I have found a new site with geodes that appear to be lined with an opaque yellow to creamy white stone. For lack of a better description, it looks something like chewed gum, or bubbling melted cheese. Can anyone suggest what kind of rock they may be?

Anonymous said...

where at around Livingston should I look. I am planning a trip to Monterey next week.

Systemechanix said...

I have found one small geode on a mountain side ,pretty high up in Big tone Gap va, . I was actually looking for one in clay . I dug down about four feet or so and when I was clearing out the dirt I found a small round rock , kinda squatty but completelt round . Is clay the best place to look for them ? Very new rock hound please help me @ mechanic69_@hotmail.com
Thank you systemechanix.

KR said...

Hi, I'm finding "concretions" and "nodules" in red clay along roadsides not far from Dunbar Cave, Clarksville, TN. Some are flatish like a disc, others like a broken-off doorknob, some like eyeballs. Cross-sections of larger ones have rings. One like a golf ball. Anyone found geodes near here?

sysmech said...

Sysmech I found the exact same type of rocks. In Big Stone Gap. Many diffrent sizes though. And some of mine are the same Mine have veins of quartz or manycolors some are orangeandred some yellowish color. I'm searching on A moountain about 1800 ft above sealevel. These were created as beached were drying up. Some have skeletons of fossilized animals in them. Mine look like turtle shells kinda . I love to hunt for them. I find them alot aroung old trees and in clay . Lots of fossils. Mostly marine . Sorry wish I had a PIC TO SEND .

argon(one) said...

I find an abundance of geodes in the middle Tennessee area, especially between Nashville and Cookville [from I-40 north all the way to the Kentucky line]. Happy hunting!

argon(one) said...

If you leave a comment here, please state it in English, since that is the only language I understand. Because I cannot determine the content of a comment left in a different language, I must delete it.

Nothing personal, I just want to make sure the comments here are family-friendly. Thank you for your understanding.

Anonymous said...

I'm heading down to Saint louis for business in june. Do you know exactly where i could go geode hunting. And if i fail to find one do you know of any stores in Missouri that sell geodes?

Thanks
Sean

argon(one) said...

If you will be anywhere near Kiokuk Iowa on your trip to St. Louis, there are plenty of geodes to be found around there. Just ask around town and I'm sure you can find a location to explore.

Becbec said...

Am finding various colors of blue
geodes on Mom's farm in Franklin TN. While bulldozing a rock shelf, the abundance of crystals and blue are amazing. What should I do with them? becky121151@hotmail.com

Becbec said...

While bulldozing on Mom's farm in Franklin TN, seem to have uncovered a trove of geodes, some amazing blue colors. What should I do with this find?

Anonymous said...

I have come across some very interesting rocks in Costa Rica, also petrified palm tree, crystals and geodes. I was told that in Costa Rica they were very scarce but I have found real nice amthyst, and large Crytsals, would like to know how to go about selling a few and if they would be of interest.

Dee said...

Geodes are all over Lawrence County. I personally have several as large as bowling balls and have orange, yellow and purple these last three are very small though. And to Becbec I would love some of the ones you are finding. Please get in touch.

Anonymous said...

iverWe just found a Geode in our backyard in Charlotte Tn.
It's filled with white/clear Quartz crystals.

@AmericanGeode said...

We excavated ours from crazy steep hill in Heltonville, Indiana. Not to direct anyone away from this great blog, but we have maps of where geodes are found in North America, and in Indiana. It's interesting since so much of it has to do with where the glacial prehistoric ice cap was, and where it melted. So that kind of information on our site and twitter. Thanks.

Geodes Rocks said...

Geodes are natural inorganic objects which are hollow. Geodes are usually roughly spherical in shape and can occur in igneous or ... geodesrocks.blogspot.com