Showcasing Cottonwood River collection

Eibner is new guest curator at Brown County Historical Society

William Eibner stands with his Guest Curator display cases, which showcase numerous mineral specimen types he’s collected from the Cottonwood River. He said it is imperative to rescue fossils and minerals from these waterways before they are churned by the waters and slowly disintegrated.

NEW ULM — After seven years exploring the Cottonwood River, William Eibner is getting the chance to show what he’s found.

Eibner is the new guest curator at the Brown County Historical Society. His exhibit will be on the second floor of the museum until the end of March. Eibner’s specialty is minerals and fossils.

“These are all rocks found in the Cottonwood River over a seven-year period near New Ulm,” he said. “I’d gotten permission from the landowners to gain access to wherever and if there was a permit required I made sure I took care of all that. You got to check with where you’re hunting.”

Eibner said he was initially attracted to exploring the river to get away from the troubles of life. Since then, he has learned a lot about the area and the types of specimens that can be found.

“There’s three things you can find out there,” Eibner said. “What I call semi-worthless gemstones, and then fossils and artifacts. The fossils and the artifacts may or may not be significant.”

Eibner arranges some of his specimens before placing the holder back in a display. Some artifacts he pointed out include a 65 million-year-old leaf fossil and a jar of Bison teeth.

There is a whole host of different minerals, rocks, and fossils that can be found in the area. Eibner said a lot of them ended up there after the last ice age.

“I know the Cottonwood River was formed after the end of the last ice age,” he said. “You can imagine there was a huge glacier; the edge of it was right on the northern bank of the Cottonwood River. That’s why most of the streams feed in from the south. It may have acted like a bulldozer and left a lot of the stuff and the river is moving it around.”

Eibner said he chose the Cottonwood River to study and obtain minerals mainly out of convenience. But after further inspection, found it to be a unique river due to how violently it floods despite its smaller size. He said this tendency makes it easier to find different specimens, as it brings in new pieces waiting to be plucked out.

Of what he has on display, one of the most surprising finds for Eibner was a 65 million-year-old leaf fossil within a siderite concretion.

“It formed around this leaf fossil in here,” he said. “This would have been in danger of getting eaten by dinosaurs. Being that the margin is preserved, you can tell it’s a smooth margin. That gives you an idea of the temperature, the climate at the time this leaf was growing.”

Eibner showcases some Honey Agate stones he found while exploring the Cottonwood River. He has been exploring the river since 2017, and has accumulated hundreds of varied specimens during his time.

Eibner also has a jar of Bison teeth on display. He said he is excited about the future usage of these teeth and the information that can be gleaned from them.

“Because they grow from the bottom up and if you go layer by layer isotopic analysis, you could trace to where that animal was in its life as it grew up,” Eibner said. “In the future when these types of tests become inexpensive, teeth like these will be really valuable because you can do a mass analysis of a whole bunch of data.”

Eibner said he’s never had the chance to showcase the results of his hard work before. He hopes it inspires others to collect and preserve minerals and potential fossils they find.

“[Unless] you’re doing that this stuff would be consumed by the river,” Eibner said. “It slowly works its way to slower moving water and it gets buried and sequestered forever eventually or broken down until it’s completely gone.”

For those interested in hunting for specimens like Eibner, he said obtaining permission from area landowners is key because during exploration one is bound to stumble onto private property. Eibner said to be wary of the dangers of exploration on the Cottonwood such as getting lost, dehydration, and quicksand. He also stressed to not explore when the river is flooding.


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