Sandstone is a sedimentary rock composed of sand-sized minerals or rock materials. It is mainly composed of quartz and/or felspar. This specimen shows a fault in the sandstone. A fault is a planar fracture (discontinuity) in a rock as a result of a mass movement, causing the displacement. Here you can see how the lined pattern does not line up correctly across the sandstone. This specimen was found in Andreasberg, Germany within the Harz, the largest mountain range in the country. It was given to the GRPM as a gift from the United States National Museum of Natural History.