St. Peter Sandstone
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St. Peter sandstone is an Ordovician formation in the Chazyan stage of the Champlainian series. This sandstone originated as a sheet of sand in clear, shallow water near the shore of a Paleozoic sea and consists of fine-to-medium-size, well-rounded quartz grains with frosted surfaces. The extent of the formation spans north-south from Minnesota to Missouri and east-west from Illinois into Nebraska and South Dakota. The type locality for the formation is St. Peter, Minnesota. In eastern Missouri the stone consists of quartz sand that is 99.44% silica.
St. Peter sandstone is or has been mined in Pacific, Festus, Crystal City, Augusta, and Pevely in Missouri, and at Ottawa, Illinois. It is used for the manufacture of glass, for filter and molding sand, and for abrasives. Its purity is especially important to glassmakers. It is also important as a "frac sand" in oil and gas drilling – loose sand is pumped in a liquid mix under high pressure into a well where the sand grains wedge into and hold open any fractures in the rock, enhancing the extraction of hydrocarbons.
References
- Unklesbay, A.G; & Vineyard, Jerry D. (1992). Missouri Geology -- Three Billion Years of Volcanoes, Seas, Sediments, and Erosion. University of Missouri Press. ISBN 0-8262-0836-3.