Southern Indiana at heart of nation’s limestone suppliers
By Sarah Boyum
Indiana limestone is used on many campus buildings, including the Indiana Memorial Union, Rawles Hall and Simon Hall, according to “Follow the Limestone: A Walking Tour of Indiana University,” compiled by Brian D. Keith of the Indiana Geological Survey.
Indiana limestone is prevalent in Monroe and Lawrence counties because it is exposed at the surface and is easiest to quarry in these locations due to the erosion of rock layers formed during the Mississippian Era.
Salem limestone, referred to as Indiana limestone, has been locally quarried in Monroe and Lawrence counties since 1827 and was accessible for building on the IU campus.
Todd Thompson, member of the Indiana Geological Survey, said the formation of this particular limestone in Indiana began approximately 340 million years ago, when parts of southern Indiana were covered with warm and shallow tropical waters.
After the tropical waters receded, the different layers of rock, including limestone, formed. Similar to most limestone, Indiana limestone is primarily composed of calcium carbonate.
Unlike other types of limestone that include fossils or big shell materials, Indiana
limestone is fine-grained and uniform in all directions. Thompson said this is why it’s used for building purposes.
The rock itself is relatively soft and easy to cut and carve into shapes. Because of the uniformity of grains, Indiana limestone doesn’t fall apart into layers when it is drilled out of the ground.
To quarry it, holes are drilled along the edge of the stone and huge blocks of the limestone are broken off. But only a small amount of quarried stone is usable.
“If they can get 25 percent recovery in a quarry, they are ecstatic,” Keith said.
Much of the quarried stone is unusable due to blemishes or fossils in the limestone.
Additionally, many residential areas sit atop the Indiana limestone in many parts of Monroe and Lawrence counties. The limestone, buried underneath new houses, is lost as a resource.
Still, there isn’t a lack of Indiana limestone.
“We’ve got 100 years of stone to quarry,” Keith said.
Kathryn Shaffer, minerals statistician at the Indiana Geological Survey, said Indiana is one of the biggest suppliers of limestone in the nation.
“Indiana usually ranks first in the nation in dimension limestone production,” Shaffer said. “It is considered a premier building stone that has been used extensively in construction of many of our nation’s best-known buildings.”
Famous buildings bearing Indiana limestone include the Pentagon, the National Cathedral and the Empire State Building.