June 16. Indiana Limestone

Much of the Mississippian limestone in southern Indiana is uniform in its color and texture, properties that make it an excellent building stone. It’s used in many monument facings too. The Empire State Building, National Cathedral, Chicago Public Library, Metropolitan Museum of Art, the new Yankee Stadium, and the roof of the immigration building at Ellis Island are all Indiana Limestone. 35 of the 50 state capitol buildings feature Indiana limestone. 

Sanders Quarry in Salem Limestone

The rock is more technically known as the Salem Limestone, which formed in the warm, shallow Mississippian seas about 335 to 340 million years ago. The region was distant enough from land that very little detritus washed into the lime, so the resulting rock is more than 97% pure calcite, calcium carbonate. The rock is fossiliferous, but many of the fossils are of tiny, even microscopic animals called foraminifera. They are one-celled organisms that made calcareous shells. Most are no more than a millimeter across.

From the building stone point of view, irregularities like fossils aren’t as important as the fact that the Salem Limestone has few bedding planes to disrupt the rock. It’s massive, so blocks of the limestone can be cut out for building stone and for decorative facings. Stone used for these purposes is called dimension stone in the industry, to differentiate it from crushed stone used for things like aggregate in concrete. The rock has been quarried since 1827, and by the 1920s, something like 80% of the limestone quarried in the United States for dimension stone came from southern Indiana, mostly around the towns of Bloomington and Bedford. There are still 9 active quarries in the area.

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Today’s birthday is George Gaylord Simpson, born June 16, 1902, in Chicago. He was a prominent and influential paleontologist who contributed greatly to evolutionary theory regarding the details of how evolution takes place. He spent most of his career at Columbia and Harvard and the University of Arizona.

—Richard I. Gibson

Reference: Indiana limestone 
Sanders Quarry photo by Sphinxcat via Wikipedia (public domain).