Of the three major ingredients of clastic rocks, quartz is by far the most durable, surviving the destruction of its parent rock again and again. Once freed from igneous rocks bv weathering. quartz accumulates in layers. Grains are then
cemented together into sandstones (right) like the de Cneuv beds of the buttes in Utah's famous Monument Vallev (below). Tough though these rocks are. thev too are broken down in time. Yet it is not the sand that is destroyed but just the cement. The liberated sand now scattered on the desert floor will, in time. form new sands tones