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Claystone Geode Preliminary Scouting Trip


    A few weekends ago, Jack Kovnas and I set out to scout a locality he had discovered some years ago through an acquaintance in Tecumseh, OK. This particular locality isn't too difficult to find or get to, in fact, we were able to pull up to a locked gate and had only a hundred yards to walk down on old county right-of-way. 

    Jack's acquaintance lives only a few hundred feet east of where we parked.

    The weather was not great, but it wasn't bad either. It was a bit cool starting out but would improve as the day wore on, as would the quality and size of specimens we would discover. This particular site isn't a very big area by any means. In fact, we would discover that the best area was indeed only within about a fifty yard stretch of old roadbed cut into the native terrain, and more concentrated in an eroded area on the east side of the old cut. On Jack's previous visit to the area, it had been too wet to collect in the erosion channels. The soil here is a mix of red Permian clays that when wet is kind of like walking in biscuit dough. It sticks to everything. Fortunately, it was fairly dry, but as you can see from the color variance in the photo below, there is dampness not far below the surface.

    Also to be seen in this photo are a couple of claystone geodes in the wild. The geodes here are ancient mudballs that formed in shallow Permian seas some 280 mya. As the seas receded and the sediments began to dry out, the centers of the mudballs contracted and formed hollows that later allowed minerals in solution to precipitate crystal growth in the hollow interiors. Some of the minerals found in these geodes are calcite, aragonite, and barite in various forms. Barite seems to be most prevalent. The minerals lining the interiors of the geodes will fluoresce under SWUV.

    The size of the geodes range from 1" to 12" and are irregularly shaped, sometimes having multiple chambers. They are rarely round in shape and tend to have "fins" protruding from them, although not all of them exhibit this form. The also tend to be rather heavy for their size due to the abundance of barite, thus making them more difficult to judge the degree to which they may be hollow. Don't let their excessive weight fool you though, 98% of the larger ones (4" and up) contain beautiful hollow, crystal lined interiors).

    Although Jack seems to have a penchant (as do most) for whacking them with a rock hammer to break them, I chose to leave the ones I collected intact and take them with me to split with a soil-pipe cutter at home. This method is much less of a shock to the geodes, and produces a cleaner break along relatively even lines. It also allows for better control of the break and lessens the chance of shattering a great geode into many useless pieces.

    Jack poses here with a couple of very promising specimens which I finally convinced him would be more worthy of the pipe cutter than the crack-hammer! The following specimen photos represent a few of the geodes we collected on this recon trip.

    I have a field trip planned for the end of February for club members to collect these pretties. Due to the limited area and limited abundance of these, this will be the only field trip led to this particular locality.

2009 Virgil G Richards

Field Trip Coordinator

TRMS - 2009







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