From Ohio History Central
Ohio has an abundance of limestone and dolomite (collectively referred to as carbonate rocks) and has long been an important producer of these sedimentary rocks. Both rock types have a high percentage of calcium carbonate (the mineral calcite) but dolomite has a significant percentage of magnesium. These rocks formed as limy mud in shallow tropical seas that blanketed Ohio periodically during the Paleozoic Era. Most production of these commodities comes from rocks of Silurian and Devonian age in the western half of the state but limestone is produced from Mississippian and Pennsylvanian-age rocks in eastern Ohio.
Traditionally, Ohio ranks fourth in the nation in production of carbonate rocks and limestone and dolomite account for more than half of the annual value of industrial minerals produced in the state. They are quarried in 48 counties, annually producing 79 million tons valued at $471 million. Most of the limestone and dolomite produced in Ohio is used for construction aggregate for roads and building projects and an aggregate in concrete and asphalt. However, these commodities are an important source of agricultural lime, a fluxing agent used in making steel, cement, building stone, and many uses in the chemical industry.