FMF - Friends of Minerals Forum, discussion and message board

[Bob Harman]

I have already shown a couple of examples of doubly terminated BARYTE crystals in Indiana geodes. Here are a couple of additional examples.

[Bob Harman]

this example was found in 2013 at the Indiana rte 56 road cuts. More of a "specimen" than a geode.

[Bob Harman]

Barite and dolomite on quartz. Acquired from Dan Weinrich minerals about 8 - 10 years ago. Not very often that I find a hi quality Indiana geode available.

[Bob Harman]

The mineral calcite, CaCO3, is very commonly found in the Midwest both in geodes and other occurrences, but the equally simple carbonate mineral rhodochrosite, MnCO3, is, to my knowledge, never found in the sedimentary environment of Midwest geodes and nearby non-geode occurrences. Manganese is otherwise rather common as its oxides including "wad". These 2 carbonate minerals must form under very different conditions.
Several Midwest geode locations, however, do host occasional finds of manganese rich calcite crystals (or manganoan calcites.....are they the same????). Sheffler's Geode Mine in Missouri is, perhaps, the best known locality. An example is shown as part of the state of Missouri mineral specimens.
This example is from Monroe County Indiana and a very rare occurrence as I have never seen another quite so pink.

[Tobi]

A very beautiful calcite specimen, Bob. At first sight, it reminded me of a pink fluorite ;-)

[Bob Harman]

Another large well displayed Indiana example that some dealers wish to have the area of calcite and barite crystals culled from the remainder of the geode and offered as a non-geode specimen.

[Bob Harman]

Another nice example of a well displayed large Indiana geode with a dominant calcite aesthetically surrounded by several groups of dolomite, all on quartz. The quartz crystals in this example form nice free form growths.

[Bob Harman]

A recently collected large and well displayed example with calcites on quartz. From my private lands site in Washington County.

[Bob Harman]

When I go field collecting at this time of the year, I expect to see freshly exposed examples associated with rock falls resulting from the recent freeze/thaw episodes. So it has been for years.
These examples, from the Indiana route 56 road cuts in Washington County, were high up on the rock wall and, unfortunately, unable to be retrieved intact. The several pix of the larger example show a large 18+ cm specimen with large calcites upon bright red dolomite. If it had been collected intact and cleaned up well, it would have been a show stopper in a display case, but over several years, it fragmented and finally fell in multiple small fragments.

You can see the very porous dolostone matrix fragmenting with slices falling off the wall. If you are unlucky, one of the larger pieces might fall like a guillotine cutting or slicing off your wrist. Since these pictures were taken, both high quality examples became history; unfortunately, not all high quality examples can be successfully collected.

[Bob Harman]

The field and stream geodes from Washington County Indiana tend to be large and very large. This example is on display as part of a small geode collection in the geology building at Indiana University. As you can see it is immense in size and weighs 347 lbs. These have very limited collector appeal, only making good yard rocks or decorations such as this one. Interestingly, these very large examples tend to have very small central cavities and be dingy or rusty stained inside.

Several of the geodes on the poster are from my collection.

[Bob Harman]

An example with more collector interest is this quartz geode containing a dominant and nicely placed and nicely terminated 6.5 cm baryte crystal nestled near the "back" of the quartz lining. A smaller partial crystal can be seen in the lower right area of the cavity

[Bob Harman]

Found about 15 years ago, this aragonite consists of numerous white spiky needles on decayed ferroan dolomite in a geode cavity.

[Bob Harman]

Finding fresh geodes in the limestone matrix is the way to go for dedicated collectors and finding "field and stream geodes" in creek beds is, for novices, very common, but explaining how the geodes weather out of the limestone to wind upon the creek beds is not so apparent. Finding geodes that are in the natural process of weathering out of their matrix is quite unusual. Here is one collected about 2005.

[Bob Harman]

Bladed baryte on quartz

[Bob Harman]

An intergrown group of baryte crystals with dolomite and calcites at the 5 - 6 o'clock position.