In general, the answer is no. However, on occasion water-deposited minerals may make the enclosing rock harder and more resistant than normal to the erosional forces of nature. Thus, a localized rock promontory on an otherwise flat landscape might signal the presence of an unusual mineral deposit. Such is the case along US Highway 76, south of Waukon, Iowa, where sandstone has been cemented along a series of parallel fractures by a hard iron oxide. The result is a hard rock mass that rises above an otherwise low-relief landscape.
What are the most common Iowa minerals? The most uncommon?
The minerals which occur most abundantly in the bedrock at the surface in Iowa are calcite and dolomite. These two carbonate minerals are the stuff of which limestone, which is quarried all over the state, is made. The most common mineral in the surficial deposits (stream and glacial sediments and soils) is quartz.
Your chapter about Iowa’s mining industries was fascinating. Many people would be surprised to know that, at its peak, coal mining was second only to agriculture in the state. Given the fact that demand for coal remains high, do you foresee a resurgence in the industry in Iowa?
Without question, there is still a lot of unmined coal in Iowa. (I found that out through some studies I did on Iowa coal reserves for the United States Bureau of Mines back in the mid 1970s.) The problem with Iowa coal is that the coal layers are thin (a few feet thick, at most). In addition, the coal is very high in pollution-causing sulfur, and removing it is expensive. At present, Iowa coal cannot compete with the enormous deposits of cheap, low-sulfur coal that are being mined in Wyoming and Montana. When they run out, who knows?
Paul Garvin, Iowa’s Minerals: Their Occurrence, Origins, Industries, and Lore
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