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March-April 2017

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Midwest Mineral Rarities

The request for this article sounded like a fairly straightforward assignment, but the simple three-word title poses three awkward questions. First, where exactly is the Midwest? Its definition has been viewed from several different perspectives. Some think of the Midwest in terms of geography—as an area where rivers (the Mississippi, Platte, or Ohio) and mountains (the Appalachians, Rockies, or Ouachitas) serve as physical boundaries. Others consider geology to be the critical determining factor. Their Midwest is typically underlain by undisturbed or gently dipping sedimentary rocks, Paleozoic through Tertiary in age, which host a suite of a dozen or so common minerals (ubiquitous quartz; simple carbonates, sulfates, and sulfides; and a few halides). The implication then is that there will be no rarities in the Midwest or that any mineral species found beyond that suite could be considered rare. In addition, a significant portion of this bedrock geology is overlain by glacial deposits and outwash, which tend to hide the “real” rocks and further diminish the possibility of finding any specimens, let alone rare ones.

Janet H. Clifford is a geologist by training though not by profession. An avid mineral collector for more than forty years, she enjoys field trips, exhibiting at mineral shows, volunteering at the Cleveland Museum of Natural History, and occasionally editing or writing for the hobby.

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