MIDWEST USA SEDIMENTARY TYPE GEODES

The first pix is SMYTHITE in BARITES. The smythites are the 1mm six sided plates and were formerly thought to be marcasites. This geode represents one of my very first "modern" finds, from before 1995, and was prepared badly, but as I used polyurethane spray to stabilize it, I have never tried to undo it and re-prepare it. The second pix is of a 4.0 cm Brown County Indiana geode with GOETHITE. Note its similarity to the one Ken V posted. Geodes from Brown County tend to be small with micro minerals. The third pix is of a 9.0 cm geode containing groups of irridescent MARCASITES and questionable PYRITE on DOLOMITE. This is from Monroe County 2009.

Ken, those photos are really good. Those must be some of the bigger geode goethites around. Bob, great rocks! My experience with smythite is that it is much more commonly found in calcite, especially at the locality north of Bloomington (roadcut 5) with the good aragonite. It could be simply that there is so much more calcite than barite encountered there. It looks like the barite/smythite you show came from the Harrodsburg area; I'll have to take a closer look at some of my specimens.

Today, an Illinois specimen:


Kaolinite in geode with dolomite and quartz from Crystal Glen Creek, Hamilton, Hancock County, Illinois. 7.5x6x4.5 cm (larger half). Circa mid 1960's.

Cheers!

Steve

DOLOMITE is one of the most common secondary minerals found in Indiana geodes, and other midwest geodes. It is found both alone and in varying combinations with other secondary minerals. In geodes from the In 56 road cuts in Washington County, dolomite overgrows quartz and the geodes become quite colorful. The dolomite saddle shaped rhombohedral crystals can vary from pearly pink thru all shades of reddish orange to brown FERROAN DOLOMITE and on to ANKERITE. Several colors can be present in the same geode as seen in these 2 pix. The first is of a large 18 cm geode and the second pix is of a 4 cm geode. More pix of this stuff coming up in the near future..........great pix everyone!!! BOB

Three more interesting and unusual Indiana QUARTZ geodes. The first pix is of an esthetically pleasing evenly and delicately hematite colored tips of the quartz crystals in a 12 cm specimen. Almost always geodes with stained crystals are unappealing and not of display quality; some are even sold as "citrine", but are just rust stained ordinary quartz and not really of any enhanced value. The second pix is of a small 3.5 cm geode called a "pinkie". These geodes are always small and the crystals have a decidedly pink hue; not quite rose quartz, but pinkish hue never the less. Most also contain small pinkish gray calcites. They can even be recognized prior to opening as their outside is very lumpy bumpy, and when cleaned, is vaguely pinkish gray in color. The third picture is a very interesting 13 cm geode of crystalline quartz on blue chalcedony (microcrystalline quartz). These are very rare and, I suppose, an unusual variant of the dew drop diamond variety described by me with an earlier picture. CHEERS................BOB

Bob, thanks for showing me your fine collection again. Hope you don't mind me sharing the pictures I took of one of your Indiana smoky "dew drop diamond" geodes. The quartz dipyramids are as fine as any I've seen out of the Keokuk area.

Another from the 'aragonite' locality north of Bloomington in Monroe County, Indiana. The overall size is 8.5x7.5x6 cm but because of the thick inner layer of dolomite the opening is only 4.5x3 cm. Calcite rhombs with minor smythite-pyrrhotite on dolomite.



Cheers!

Steve

Every field collector dreams of finding one or some very hi quality specimens.......stunners. Well, over the years some collectors' dreams do come true. In this case, the first pix is of one large Indiana geode that I found two years ago. It measures about 20 cm x 13 cm and is from a high banked stream bed in Washington County. There are mounds of pristine ARAGONITE on pristine QUARTZ. The second pix is of an Indiana geode found in May of 2005 at the Harrodsburg road cuts (see pix in "The Nature Thread") in Monroe County. It was found by a fellow collector and purchased by me. This geode measures about 19 cm x 18 cm and contains an isolated 4.5 very lustrous transparent BARITE and a nearby isolated 7cm CALCITE rhombohedral crystal. Both these geodes were recently shown to a high end dealer who was interested in acquiring them, but wanted to trim the interesting parts of both, thus sacrificing the geodes. Most of us have, at large shows, seen portions of amethyst "geodes" trimmed to show calcites etc or good crystal portions trimmed out of large Madagascar celestine geodes. These are then sold as "specimens" rather than their true geode type environment to enhance their values. To date, I have elected to keep these geodes intact and not trim the high quality areas from the rest of the geode. Enjoy..............BOB

My case at the 2011 Cincinnati show. This case shows some of my display quality Indiana geodes from the route 56 road cuts just East of the town of Salem in Washington County. These geodes often have yellow through brick red DOLOMITES upon which significant CALCITES occur. Also found are SPHALERITES and occasional BARITES, a couple of which are pictured. As such, these geodes are routinely quite colorful and often medium to quite large in size. Ordinary QUARTZ geodes also are regularly found, but in only one layer near the road level. Collecting is best in mid winter thru early spring as the rock loosens up with freeze/thaw cycles. Collecting is poor thru the summer months, but as I write, a number of very hi quality specimens are currently (and at most times) still in the high wall about 12 to 25 feet up. Repelling down from the top or use of a lift at the roadside might reward a determined collector! But don't expect help or encouragement from the police or highway department! Whole geodes are quite uncommon as the rock layers scale off naturally splitting most geodes into slices or 2 halves as seen here in the case. All these were self collected as depicted, with none cracked open over the past 10 years or so. Enjoy...........BOB

Bob,
So there are geodes from the mid west that are better than yard rock. Who would have guessed. Those are two really amazing geodes. I sure wish you would upload those and images of some of your other geodes to the mindat general gallery so I could put them in the Best Minerals articles. If you need help on how to do this uploading, you can read about it by clicking here: Uploading specimen images to Mindat.

Rock Currier
Crystals not pistols.

ROCK I have not been ignoring your pleas for me to upload some images of my best and most unusual Indiana geodes to your permanent file site, but there are several situations that presently command much of my time. Also, I am not very computer literate, having had help walking me thru even these simple steps. I may get that help again when I have the time and then the uploading would begin. Thanks for your interest; watch for more pix in the coming weeks and months. BOB HARMAN

For Indiana geode collectors, and indeed many midwest geode collectors, MILLERITE and its oxidation products including HONESSITE are highly sought after. The first pix is of HONESSITE (?) on QUARTZ in a 13 cm specimen from Monroe County. Its absolute identification is part of a rather jumbled classification of the oxidation products of millerite. Note the bright grass green color of the crystal sprays. The best spray actually just pokes out from beneath the quartz in the lower center of the photo. The second pix is of a 1cm symmetrical bright brassy MILLERITE spray nestled in a 9 cm Quartz geode from Monroe county. Both were found at the Harrodsburg road cuts. When Indiana state route 37 South of Bloomington was widened to 4 lanes in the early 1970s, quite a few high quality millerites (and barites, calcites etc) in geodes were found. I have talked with one of those collectors and he recounted his adventures collecting many geodes as the road work proceeded......what an adventure for him and his collecting buddies! The construction site is said to have swarmed with collectors on weekends. These specimens went to numerous museums and private collections. Visiting several museums on my travels, I have seen a couple of them, dated to that road widening time frame.

In November of 2007 during construction of a small retention pond in a new housing subdivision near Bloomington, Indiana, very fresh geode bearing rock was exposed. I had 3 days to collect as the heavy equipment contoured the 1 acre site and crushed up the surface rock, then covering it with gravel. Now it is an extinct site intermittently filling with water after heavy rains. The geodes are quite distinctive, showing pearly pink dolomites upon which colorless to pale cream colored calcites occur. These often have a "satiny" surface patina, as seen in the second pix. Some out there who know Midwest USA minerals might see a resemblance of the first pix with Corydon Indiana quarry calcite and dolomite non-geode specimens. However, these are true geodes as all have a quartz rind and most show some very fresh crystalline quartz as shown in the second example. I gave one example to a friend and sold (regretfully !) one additional example at a local show; I believe only we three people have geodes from this short-lived site.

These 3 geodes were found several years ago in my favorite ARAGONITE location in southern Monroe County, Indiana. The first pix shows an 10 cm x 4.5 cm specimen with the largest ARAGONITE grouping bridging the cavity. A smaller spray can be seen in the background as well as scattered hemispheric coatings on the QUARTZ crystals. The second pix shows halves of 2 geodes one is 7 cm; the smaller is 3.5 cm. Each shows advanced decomposing FERROAN DOLOMITE/ANKERITE, still crystalline, with some ARAGONITE sprinkled on the tips of the underlying crystals. Note the similarity to the old LIMONITE classification, especially in the broken crystal areas.The third pix is a close up of the geode on the right in picture #2. Enjoy......BOB

The accompanying pix show an unusual geode type found in Indiana and also in Kentucky and Illinois. They are geodized fossils. One theory of geode formation involves fossils decaying in the mud and their void being slowly replaced by a quartz rind and a central cavity. However these form, they are quite interesting and, in Indiana, found most commonly in Monroe, Washington and Lawrence counties. They are of gastropods, brachiopods, cephalopods, horn corals, crinoids and various shells. They range from several centimeters to many centimeters in size in some locations. The very best ones, as shown here, show remaining good fossil detail with parts of the original shell incorporated into the geode. Most are examples solid, but occasional examples are hollow with Quartz crystals as in an "ordinary or usual" quartz geode. For a hollow example, see my previous pix on page 2 of this thread with a smoky dew drop diamond variety. Enjoy..................BOB



Edited 1 time(s). Last edit at 04/17/2012 09:29PM by BOB HARMAN.

Bob,
You should really upload your images to the Mindat Image gallery. Then you could put them to gather as an article or as a Best Minerals article. Did you see the one that Harjo Neutkens did on Schalenblende?

[www.mindat.org]

Rock Currier
Crystals not pistols.

Sulfides as secondary minerals in Indiana geodes are quite common and include SPHALERITE, PYRITE, MARCASITE, and MILLERITE. Also there are less common oxidation minerals and minor minerals. Millerite and marcasite examples have been previously pictured and pyrites tend to be small and not very showy. However, SPHALERITE can be quite showy. The best come from Monroe and Washington counties. They are quite common in geodes from the Harrodsburg roadcuts, but are very rarely found as free standing crystals; most being cleavage portions embedded within calcite and dolomite in solid geodes as pictured on the right of the second picture. Good free standing crystals up to 3 cm occur at the Indiana route 56 road cuts in Washington county and one is pictured in the first photo. The best from Monroe county seem to occur in geodes from the Unionville railroad cut, Northeast of Bloomington. A 1 cm example is on the left of the second photo.

Bob, excellent photos & geodized fossil specimens !

I happened to find my best ever chalcopyrite on calcite Keokuk geode in Lee County, Iowa on my last collecting trip. The geode is 11 cm in diameter and the largest group of interjoined/twinned chalcopyrite crystals in the last photo is 1 cm across. You will also see some enlogated cubes of pyrite or marcasite in it as well.

In many of my previous pix of Indiana geodes (but by no means all of them), I have shown one secondary geode mineral in addition to the QUARTZ. In fact most display quality Indiana geodes have various combinations of 2 or more secondary minerals present.These 3 pix show BARITE and DOLOMITE in the quartz geodes. All three are from the Harrodsburg road cuts in Monroe county. The first pix shows a 12 cm x 7 cm geode containing several DOLOMITE groupings along with a stout 2.8 cm x 3.0 cm color zoned barite. There is a visible internal crystal fracture in the barite which is quite common. Found in February of 2007. Pix number 2 shows a 14 cm x 9 cm oval geode with orange DOLOMITE groupings and rim surrounding innumerable jumbled BARITES. Of interest is the fact that the barites exist mostly in the lower (bottom) portion of the geode, probably due to gravity and their weight during formation. This half fell to the roadside after a freeze/thaw episode in February 2000, while the other half remained slowly deteriorating in the limestone hi wall about 12 feet up for several years. Look closely and note the fossil crinoid stem sections in the adjacent limestone. Finally, picture 3 shows a 6 cm x 5 cm specimen with pale creamy DOLOMITES and pristine pale yellow transparent BARITES. It was found in the 1970s or 1980s by another prominent midwest collector and purchased by me about 2009. ENJOY......BOB



Edited 1 time(s). Last edit at 04/21/2012 08:15PM by BOB HARMAN.

Two more Indiana geodes from Monroe County. The first pix is a 20 cm example with CALCITES, including a 5.5 cm one, groups of BARITE and groups of interesting dark chocolate brown FERROAN DOLOMITES. Acquired by me from a fellow collector who found it in 2008. The second pix is of a 19 cm x 15 cm example with a complex group of CALCITES, BARITES, a few DOLOMITES and a small SPHALERITE (seen in the lower left of the photo). Acquired in 2004. These 2 examples show additional examples of the complex mixtures of secondary minerals commonly found in Indiana geodes

Several other spots in southern Monroe County, Indiana produce geodes quite similar to those found at the nearby Harrodsburg road cuts (several examples already previously pictured here). Also, see some recent pictures of the Harrodsburg road cuts in the "Nature Thread". The first picture is a 17 cm x 14 cm geode with several CALCITES, including two 5 cm rhombohedral examples, adjacent 1.5 cm to 2.5 cm BARITES and a few small DOLOMITE groups are also present. This example was found and extracted with a stone saw by a fellow collector in 2008 at the "Barite Hill" locality. The site's name is only used by geode collectors as many barite containing geodes have been found there. This is a very short road cut whose overhang is now collapsing and may make the site extinct within the next several years. The second pix shows 2 geodes, the larger of which contains a flat lying 6.5 cm CALCITE and a nearby 2.5 x 3.0 cm free standing pale yellow to colorless BARITE. Several small calcites also occur. This geode is from the early1980's at the Monroe Lake spillway when collecting apparently was allowed. Some time after 1990, collecting of geodes and fossils at this site and along Lake Monroe shorelines became forbidden. Parenthetically, here is an interesting story about collecting along the lake shoreline. About 11 years ago an Indiana University graduate student who collected fossils found an invertebrate specimen that neither he nor anyone else recognized. He showed it all around and it was eventually sent off to an out of state expert in that fossil area. It was considered a significant new species and written up in (I think) the periodical "Nature" about June 2002. He then made the mistake of showing all this to the local Bloomington newspaper and a big article appeared about the fellow and his new local fossil species find from the lake shore. Well, within several days the Indiana conservation officers came knocking on his door and gave him 2 options. Be charged with illegal fossil collecting or donate the specimen to the museum and stop collecting. Not positive, but I think his specimen now resides in the Smithsonian. Currently you need a collecting permit, but, as far as I know, no one manages to get one!. CHEERS.........BOB