MIDWEST USA SEDIMENTARY TYPE GEODES

The Cincinnati, Ohio show was last weekend and these are 3 pix of my case. The show theme this year was "Carbonate Minerals" and my case displayed these minerals in Indiana geodes. The show was well attended and all the exhibits, along with my case, were of high quality and well received. The closeups show several calcite and dolomite specimens. Also in the case were several aragonite specimens along with a strontianite and malachite containing geode (very rare but not very showy). Some of these examples have been pictured on this thread before, but for several others, it is a first time. CHEERS.............BOB

Bob, You should really get your images and your knowledge of these thing published some where. If not on the increasing diminishing realm of paper, then on line somewhere. You could write an article like the Best Minerals articles here on mindat. I would love to help you write an article on these geodes for our Best Minerals articles. Take a look at what Harjo Neutkens did with Schalenblende. [www.mindat.org]

Rock Currier
Crystals not pistols.

While the vast majority of Indiana geodes are round to oval, not all are. In several highly fossilized areas of sandy siltstone in Southern Monroe County, the geodes can be so numerous as to become multi-chambered like the 2 pictured here. These geode cavities can be entirely separate from each other or interconnected in complex patterns. Fresh ones are rarely encountered as many that reach the outside surface become weathered and allow rust and mud to enter all or portions of their chambers as seen in the second pix. Note the accompanying ruler for scale; some areas are one to two meters across. Aragonites are usually associated with these geodes and a 1.8 cm needle is seen protruding into the geode cavity of the second from the top in the first pix. Being associated with a highly fossilized (mostly crinoid stem) area supports the thesis of geodes developing from cavities of decaying fossils. CHEERS............BOB

This is one of the largest Indiana geodes ever found. It weighs about 347 lbs and is from Washington County, where most of the very large Indiana geodes come from. As these geodes are rarely, if ever, of display quality when opened, and so very bulky and heavy, they have virtually no collector value. They are sold unopened, by the pound at garden supply stores around this part of the Midwest. This one is part of the geode display in the geology building at Indiana University. See my other pix with a more complete description of these oddities in the "MONEY GRUBBERS.....want a valuation of my geode" thread. CHEERS.........BOB

All of us have seen , at mineral shows, large amethyst "geodes" and large celestine geodes from Madagascar. In dealer display cases, most of us have seen particularly nice cabinet size specimens of celestine crystals and calcites on amethyst culled from these large geodes. The same occasionally holds true for large Indiana geodes. These 3 pix show collectible areas culled from badly broken large Indiana geodes. The first pix shows several nice rhombohedral calcites and some dolomite all on quartz. The specimen measures about 22cm x 15cm and the calcites up to 4.5cm, from Monroe County. The second pix shows a group of scalenohedral calcites, up to 4.5cm, containing numerous marcasite inclusions and numerous accompanying small barites in a 24cm x 18cm geode portion. Also from Monroe County. And the third pix shows, from another collector's 2012 Cincinnati display case, a 5.5 cm group of very lustrous barites with associated quartz that had broken apart when the geode was found and opened. I also have, and have seen, many other display quality specimens both culled from large geodes and unavoidably broken away in geodes as they were opened. The moral here: nice display specimens can still arise from the ashes of otherwise destroyed geodes. CHEERS..........BOB



Edited 1 time(s). Last edit at 05/18/2012 02:04PM by BOB HARMAN.

Really enjoying this thread, Bob. I had a chance about 10 years ago to spend a few hours collecting geodes in your area. Nothing anywhere close to this impressive, but your last comments resonated - my two best pieces, both thumbnails, are a ca. 1 cm barite and a calcite of about the same size, both absolutely perfect in little partial quartz-lined pockets, that I found lying in shattered pieces at the base of the cliff. To complete the Indiana collecting experience, I headed to the fossil crinoids in one of the roadcuts east of Evansville (as I recall), where I found some nice pieces and was bitten by a mosquito that gave me some nasty virus. Wasn't West Nile, but I only learned that after a negative spinal tap. Ahh, fond memories!! --Ken

KEN Thanks for your kind words. As you can see much of what I have and show is self collected, but I do occasionally buy to enhance my focused collection. To make the experience complete, I try to add some comments to the pix for a learning experience, especially for those in other parts of the USA and world. I was hoping others with great Midwest Geode display specimens would be motivated to add to this thread, but I have not so far been too successful. And there are others out there with great photogenic specimens. And I too occasionally come home with "friends". Ticks are common, I have seen a Black Widow Spider (females aggressively guard their nest!), and a small area of poison ivy is on my leg as I write this. Last year I had a non-specific reaction to a tick (???) with an unusual itchy rash that only gradually went away only after several weeks. Of course there are the ever present bruises and cuts and after collecting aches. Still fun !! CHEERS...........BOB

Bob,

I am running out of geodes to picture for this thread. Maybe I need a trip to Indiana for a new supply!

I like the classification of geodes you pictured above. This one would be in the mature category.

This specimen is from the aragonite road cut on old RT 37, 5.25 miles north of Bloomington in Monroe County. Collected in about 1966. It contains a large group of chubby calcite rhombs, frosted quartz, a bit of aragonite and ankerite. The orange color in the calcite in the lower center is an alteration (pseudomorph) of included millerite hairs. 18x11x11 cm.



Cheers!

Steve

This Indiana Geode containing considerable MARCASITE was etched out of enclosing calcite and acquired by me several years ago. Many Indiana geodes contain massive enclosing calcite that can easily be etched away revealing otherwise hidden other secondary minerals. When the minerals include sulfides as seen here, the adjacent quartz is almost always stained by iron; this is very difficult or impossible to remove, even using various rust removing chemicals.

The Indiana route 56 road cuts in Washington County, about 7 miles East of the town of Salem. This is the South road cut and as such, faces North. It is perpetually in the shade during the winter months so, after cold spells, much ice remains well into the warm spells. The rock layers split and rock falls are common as large slices can look like guillotines as they fall. The second pix shows a large, nearly 12" geode half still in place last week (May 22). It is about 15 feet high up in the rock wall. It originally was a very hi quality red dolomite geode with large calcites on the dolomite. The other half fell 2 seasons ago and was collected by me. This remaining half was the better one, but, as you can see, it will gradually deteriorate in place, falling as slices over the next several seasons. Only repelling down from the top or using a roadside lift would have helped extract it, but don't expect any help from the police or highway folks! A really great Indiana geode specimen destined for natural oblivion..........CHEERS....... BOB

This 7 cm dew drop diamond geode with a smallish 2.3 cm central cavity is, in most ways, not very special. Except for the isolated 0.6 cm pristine perfect bipyramidal quartz crystal that I have attempted to photograph. The quartz crystals in these type geodes are rarely of this size and, in person, this one really stands out. Self collected from Monroe county in 2001. CHEERS...........BOB

As yesterday was perfect for Indiana geode collecting, I was off to one of my favorite aragonite sites along a creek bed on private land in Southern Monroe County. The first pix is of most of the unbroken examples that I brought home. As a rule, I break the small ones, the very large ones and the heavy feeling ones right at the site. Experience tells me that most of these I will leave at the site, but I wrap up the infrequent hi quality ones that I break in the field. As my threshold for keeping these geodes is now very high, I don't expect to find many that I will keep. The non-keepers I wholesale or sell off to other friends. My second pix is the broken ones that I will save for further exam, not making any quick decisions here. These geodes have the expected aragonite and ferroan dolomite/ankerite found routinely at this site. While nice, they are unfortunately nothing really special for me. There is also a quartz geode with really nice delicate stringers of small crystals on top of an earlier generation of larger quartz crystals. Adjacent to this sandy siltstone deposit of aragonite containing geodes, there is a good area for collecting local fossils. The third pix shows 2 plates of crinoid stems, a brachiopod and a geodized crinoid stem that I found as well. All my fossil finds are given away or sold very inexpensively to fossil collector friends. CHEERS.............BOB

Hey Bob this is Byron from up north of you (fort Wayne) some day we have to hook up and do some collecting down there.
I also need to get off my butt and get some pictures posted of the geodes i have found.


Byron

I'm adding pictures of some of my better geodes Bob. My Indiana collection has a lot to be desired, but I have several here from Keokuk, Iowa and Deming, New Mexico. The first one in this group is a great looking 9 inch Red druze Rhyolite geode from the Baker mine in Deming, N.M. The pictures don't show it very well, but the second geode is a 11 inch Diamond dew drop from Keokuk. The third one in this group is a 2 chamber rhyolite geode from the Baker mine in Deming

The first geode in this set is a larger geode from Keokuk, Iowa with a group of large calcites. The second one is a amethyst Las Choyas and the third one is another Baker mine Geode from Deming

This is a really nice geode with a great looking calcite perched on the right side. Bloomington Indiana road cut

Every so often an opened Indiana geode is biseptate as seen in the accompanying picture (hard to photograph as the 2 cavities are at an angle to one another). This geode, from Monroe County, is 18 cm x 17 cm. The left side cavity contains a 7 cm calcite rhomb and a bit of barite fragments on quartz while the right side cavity contains a couple of 3 cm calcites and some pale pearly pink dolomite aggregates on the quartz. CHEERS.............BOB

i found this while fishing in missouri ,can anyone tell me what it is and if it has any vaule?

TOMKATT As there are no pix or description of any kind accompanying your brief blog, no discussion is possible.

Also, this theme is primarily meant to show unusual and display quality Midwest USA geodes. I suggest redoing your blog with a description and picture or two on the "money grubbers" theme if you are primarily interested in the value of whatever you have found. CHEERS...............BOB HARMAN

ARAGONITE in Indiana geodes takes many forms. The first picture shows the ARAGONITE coating nearly all the QUARTZ with numerous complex needle groups as well. There also is considerable accompanying FERROAN DOLOMITE/ANKERITE. This geode is 15cm x 7.5 cm, from Monroe county in 2001. The second picture shows most of the Quartz lining this geode to be uninvolved, but groups of hemispheric ARAGONITES coating areas of the QUARTZ. The geode is 8.5 cm x 8.0 cm, from Monroe County about 2004. Both geodes are from the same sandy siltstone site. CHEERS...........BOB