Soils composed mostly of primary minerals will tend to have a higher percentage of sand and a lower percentage of clay than soils composed mostly of secondary minerals.
Soils are porous medium that are made up of minerals, organic matter, water, gases, and microorganisms. Soils are mostly composed of minerals (about 45% to 49%) which are derived from two main mineral types; primary and secondary minerals. Primary minerals are usually derived from igneous and metamorphic rocks in soil, while secondary minerals are produced from the weathering of the primary minerals. Soils that contain mainly primary minerals usually have high amount of sand and silt, and a low amount of clay than soils that contain mainly secondary minerals. Examples of primary minerals are K-feldspars (such as sanidine and orthoclase), and micas (such as biotite).
