An Introduction to Soil Mineralogy

make up about 50% of the volume of most soils. They provide physical support for plants, and create the water- and air-filled pores that make plant growth possible. Mineral weathering releases plant nutrients that are retained by other minerals through adsorption, cation exchange, and precipitation. Minerals are indicators of the amount of weathering that has taken place, and the presence or absence of particular minerals gives clues as to how soils formed. The physical and chemical charac teristics of soil minerals are important considerations in planning, con structing, and maintaining buildings, roads, and airports.