Sandstone

Sandstone is a sedimentary rock made of sand-sized grains of minerals, mostly quartz and feldspar, or older rocks held together by one of several types of cement or fine, muddy matrix. Sandstones vary greatly in color, composition, texture of grains, degree of cementation and layering. Common colors include grey, tan and red. Sandstones are deposited on relatively flat surfaces and are stratified or bedded. In most cases the stratification is parallel to the deposition surface, but subordinate layering may occur. Ripple marks and animal trails may appear on bedding surfaces.