MN DNR Minerals Education Workshop 2005
Field Trip guide by Dr. Dean Moosavi and Rick Ruhanen
| In this quarry the same kind of limestone is being mined for use as an aggregrate. Aggregrate is a material use in building roads or as a binder in concrete. The piles of crushed stone at the right have been sorted into different sizes in preparation for different uses.
The stone here is not used for buildings because of the smaller size in the layers. Each layer is caused by a change in the water level of the sea. When the water would become too deep for sea animals whose shells make the current stone a layer of mud would form that breaks the rock into layers. The result is rock that is not strong enough or large enough to be effectively used as a building material. |
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The rock is mined much like the iron ore in northern Minnesota but on a smaller scale. The top unwanted soil is scraped off. Holes are drilled into the bedrock that are then filled with a slurry of ammonium nitrate and diesel fuel. This mixture is then ignited which blasts the rock into small pieces that are loaded into dump trucks and brought to sorting areas. | |
