Sandstone, a type of sedimentary rock, looks like sand frozen in place. When quartz, feldspar, and other silica-containing minerals and rocks break into fragments between 0.1 and 2 mm (0.004 to 0.08 inches) across, scientists call the pieces sand. In deserts, on beaches, and under bodies of water, layers of sand grains build up over thousands or millions of years, until the accumulated pressure from the weight of those layers compact the sand grains into solid rock, a process called lithification. The sand grains are commonly cemented together by fine-grained quartz and calcite. Sandstone makes up 10 to 20 percent of all sedimentary rocks on Earth because its ingredients are among the most widespread minerals. They are found worldwide and form under a wide range of depositional environments and conditions. Detailed examination of the mineral grains and rock fragments in sandstones is necessary to help geologists interpret the source rock and the environment in which the sandstone was deposited. For example, coarser sand grains in the rock could indicate that blowing wind or running water removed the smallest, finest granules before lithification took place.

The term weathering refers to any environmental process physical, chemical, or biological that changes rocks that are exposed at Earth's surface. Scientists define physical weathering as any kind of mechanical process that breaks down surface rocks. For example, the cycle of alternating freezing and thawing of water in rock crevasses (or cracks) breaks apart rocks, because frozen water (ice) takes up more space than liquid water. Tree and plant roots also force themselves into and between rocks to break them into smaller fragments or grains. Strong winds, especially in desert environments, may pick up sand grains, driving them into exposed rocks and eroding them and leaving marks called ventifacts (from the Latin words for wind and face). In chemical weathering, weakly acidic raindrops falling on rocks and sediments cause chemical reactions, such as dissolving halite and other salts. In biological weathering, lichens, moss, and microorganisms release acidic compounds that accelerate the breakdown of rocks and grains on which they are growing.