This specimen of Hydrothermal Quartz is included in this section although it is a mineral. The small inset photo shows a thin bed of quartz sandwiched between beds of sandstone and shale,which have been uplifted to an almost vertical position. It is most probable that the quartz was hydrothemaly injected between the sandstone and shale beds because of a weakness. Note the apparent layering in the inset detail photo. There is a very large adjacent bed with very pronounced ripple marks.The location is about 200 feet above the Clywedog Dam in central Wales .