Pennsylvania's land started with the idea of plate tectonics and convection currents. The mantle of the Earth is hotter than the lithosphere, which causes materials to sink and eventually rise back up to the surface. These continents move towards or away from each other with convection currents. Then, during the Ordovician Period mountain building occurred. Convection currents that pulled the continents together formed the Appalachian Mountains. Subduction of materials causes volcanoes to form, and volcanoes eventually covered the water that left ash or Bentonite in the quarries today. Next, during the Cambrian and Ordovician periods North America still remained above the sea. Eventually weathering wore away the surface of the land, and erosion moved these sediments away. The sediments that were deposited formed limestone. Limestone is also called carbonates that are formed by chemical deposition. Limestone is made out of shells of marine animals and mineral particles and is deposited far offshore in warm areas. This formation later settles on the seafloor and turns back into rock. Mud was also deposited farther offshore creating silt and clay. These sediment particles created Martinsburg shale. At the end of the Ordovician period, sand and gravel were deposited close to the shoreline that later formed Tuscarora sandstone.
The Jacksonburg limestone and Bentonite Ash were found at the Eastern Industries Quarry. The Eastern Industry Quarry is an open pit mine, whose rocks formed around 500-450 MYA. Limestone is a sedimentary rock formed by chemical composition. The original deposit of limestone in Pennsylvania was 500 to 1,400 feet thick. Limestone may contain graphite, quartz, and calcite, but it's mainly composed of calcite and dolomite. Bentonite is volcanic ash transformed into clay. The lighter the color of ash the softer it is, and the darker the color of ash the harder it is.
