Scientists say they have discovered eight rare minerals previously undocumented in Nebraska.
"These are really exotic by Nebraska standards. The list of minerals of Nebraska has really expanded since we started doing this kind of research," University of Nebraska-Lincoln geologist Matt Joeckel said in a news release.
Scientists made the discoveries while doing research for the federally funded STATEMAP program. Joeckel noticed unusual weathering effects in shale outcrops bearing pyrite, or "fool's gold," at sites along the Missouri and Republican rivers.
Back in the lab, he and his colleagues analyzed the structure of the rock crystals using X-ray diffraction and scanning electron microscopy to establish the presence of rare minerals invisible to the naked eye.
One of the minerals they found was vashegyite, an aluminum phosphate mineral found only in a handful of locations and almost always in association with chemical reactions involving bat guano in caves.
Another discovery, gibbsite, is typically found in the tropics or subtropics. Others include alunite, aluminite and felsobanyaite.
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"What we're seeing is a living laboratory, in which chemical reactions are producing new minerals at Earth's surface," Joeckel said.
Over time, he said, pyrite (iron sulfide) in the rocks, combined with oxygen, water and microorganisms, leads to acidic conditions and the release of elements such as aluminum, iron, sulfur and perhaps even arsenic -- and the creation of some of these "weird" minerals.
Joeckel describes this process as the natural version of acid mine drainage, an environmental problem frequently associated with coal mines. Although occurring on a smaller scale and not constituting an environmental problem, the process described by Joeckel and his colleagues has broader implications for surface and groundwater chemistry.
"More than anything else, this illustrates that it's still possible to make new discoveries," he said. "We may not have volcanoes or mountains in Nebraska, but there's a lot of stuff going on out there."
The findings are published in the June edition of the scientific journal Catena.