Sandstone: 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.

When snails, corals, shellfish, and marine microorganisms die, their empty exoskeletons, rich in calcium carbonate or silica, pile up at the bottom of oceans and seas. The shells break up or decay into small pieces, called bioclasts or biochemical sediments. Over long periods of time, the upper layers of debris compress the lower layers, squeezing out excess water or air trapped between the shell fragments and breaking them down even further. Eventually, silica or calcite cements the individual fragments together to form a rock. The chalk you use to draw on the sidewalk comes from the shells of microorganisms that lived millions of years ago.

After a body of water deposits layers of sediments, the grains in those layers, or strata, undergo various changes in response to the pressure of the layers on top of them. Scientists use the word diagenesis from the Greek roots dia (change) and genesis (origin) to encompass all these changes. In the process called cementation, minerals grow or precipitate out of solution in the pore spaces between rock or mineral grains. Compaction is the collapse of pore spaces within a sedimentary rock due to the weight of the rock above it. Lithification is the process of hardening sediment into rock through compaction and cementation. Diagenesis takes place at temperatures of less than 200 degrees C (392 degrees F); at higher temperatures, scientists say that the rocks are undergoing metamorphism.

Have you eaten any minerals lately? Almost certainly! Halite is the formal name of the mineral we use as table salt. Humans use salt not just to season food, but also to cure (preserve) meats. Clay minerals, part of the silicate group, serve as mild abrasives in toothpaste, while the fluoride comes from the mineral fluorite. Finely ground silicon dioxide is an anti-caking agent in many powdered foods such as gravy mixes and non-dairy coffee "creamer." The mineral trona is the primary source of sodium carbonate, which helps baked goods rise and gives toothpaste that foamy feeling in your mouth. Calcium sulfate from the mineral gypsum coagulates (or solidifies) tofu, a soybean-based food. Many of the plants we eat depend on mineral-based fertilizers for robust growth.