The London Seminary building is built of Pennsylvanian-age sandstone. The stone is thus about 300 million years old and formed when North America and Africa were colliding to build the Appalachians as a mountain range analogous to the modern Alps or Himilayas. The sand from which the sandstone formed was deposited in a basin on the west side of the Appalachians. Such sandstones are very abundant in eastern Kentucky and reflect the tremendous erosion of sediment off the rising young mountain range.

      Close examination of the image just below shows that the sandstone has among its sand grains many small pieces of carbonaceous material. For example, the small dark horizontal black whisps visible in the image are tiny pieces of wood or other plant matter. Pennsylvanian sediments in Kentucky are rich in organic matter ranging in scale from these tiny bits to thick layers of coal. Those coal beds were deposited when swamps covered the sandy basin at the foot of the young Appalachians. Those coal beds have been mined for the last 150 years, and trainloads of coal still roll out of eastern Kentucky to fuel power plants and industries in the surrounding region.