Minnesota Mudstone & More Collection
When you work with the term “mudstone” you may find that its definition is as clear as…well, you get the idea.
Perhaps the most familiar mudstone in Minnesota is pipestone, also known as catlinite. It shares the spotlight with five additional specimens in this mudstone primer. What is and what is not a mudrock? Did you notice that word? Is it mudrock or mudstone? This is an example of just one of many conundrums clarified with this exposé. The Minnesota Geological Survey provided the technical notes below.
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Most rocks in Minnesota that are composed primarily of clay and silt sized particles are referred to as shale because commonly they contain fine horizontal laminations that formed when the rock was deposited. Mudstone or claystone are terms used more commonly for rocks that are mainly clay and silt that lack fine laminations. However the glossary of geology states that mudstone may also be used as a general term that includes clay, silt, claystone, siltstone, shale, and argillite when it is desirable to characterize the whole family of finer grained rocks (as distinguished from sandstones and conglomerates and limestones) or when the precise amounts of clay or silt in a particular rock are unknown or varies from place to place. Mudstone is not useful as aggregate because it is not hard enough, though it is used some places on country roads where there is no alternative. Shale (and/or mudstone) is mined in parts of Minnesota and used as raw material for brick or as an ingredient for Portland cement. This collection is useful to non-professionals who simply wish to learn more about the geology of Minnesota. It is not intended to be a one-stop, comprehensive collection. It is useful to anyone with an interest in earth science or Minnesota. |
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since February, 2006.