Travertine is a crystalline-textured, chemical sedimentary rock composed of calcium carbonate (calcite). It forms principally in cave environments and is the most common variety of speleothem (stalactites, stalagmites, etc.). Travertine also forms at some springs, either hot springs or cold springs.

Sometimes travertine lines fractures and joints in rocks (see example above). It will precipitate if there is a sufficient supply of calcium carbonate in overlying rocks. In this case, a thin crust of pustulose travertine is encrusting siliciclastic sedimentary rocks of the Vinton Member (Osagean Stage, upper Lower Mississippian). The Vinton is in the upper Logan Formation of eastern Ohio.