Grains of so-called “Ottawa Silica Sand” under an electron microscope. Magnification 150x. “Ottawa Sand” is a by-product of hydraulic mining of Ordovician orthoquartzites of the St. Peter Sandstone Formation of the Paleozoic intracratonic Illinois Basin.
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{{Information | Description=Sand under an electron microscope. | Source=http://exploration.nasa.gov/articles/06dec_dunes.html | Date=not specified | Author=NASA | Permission=US government, public domain }}
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