LimestoneLimestone is a carbonate rock composed primarily of the mineral calcite (CaCO3). Limestone typically forms by the chemical or biological precipitation of the calcite as a soft sediment or mud on the bottom of a tropical seabed. Limestone is seldom pure calcite but usually contains variable amounts of clay, silt, sand and nodules, or globs, of chert (SiO2). Much of the ancient limestone of the earth has been converted to dolomite (CaMg(CO3)2) as magnesium rich solutions seeped through the rocks during and after compaction and solidification. This has been the case for the abundant carbonate rocks of Cambrian and Ordovician age in the Ozark region.
Three layers of Mississippian limestone occur along the northern edge of the Bryant Watershed. These carbonate rocks have not been altered and remain good limestones. They occur only on isolated high hills along the rim of the Springfield-Salem Plateau between Cedar Gap and Mountain Grove. These are the Compton, the Pierson and the Burlington limestones. They are separated by the Northview Shale layer. The Compton and Pierson contain variable amounts of chert as lenses and nodules.