Zircon, a common mineral in igneous and metamorphic rocks, is crucial for understanding crustal evolution due to its high concentrations of U, Th, Hf, and REE. The chapter reviews the composition of zircon and its role in petrogenesis, focusing on analytical techniques and the significance of trace elements. Zircon's saturation, crystallization, and zoning are discussed, along with the influence of melt composition and temperature. The chapter also examines the major and trace element compositions of igneous zircon, including Hf, REE, P, U, and Th, and their implications for petrogenetic processes. The text highlights the importance of trace element zoning, such as oscillatory and sector zoning, in understanding zircon's petrogenetic history. Additionally, it discusses the REE patterns and anomalies (Ce and Eu) in zircon, which provide insights into the oxidation state and petrogenetic conditions of the host rocks. The chapter concludes by discussing other trace elements in zircon, such as U, Th, and Pb, and their significance in geochronology and geochemical studies.Zircon, a common mineral in igneous and metamorphic rocks, is crucial for understanding crustal evolution due to its high concentrations of U, Th, Hf, and REE. The chapter reviews the composition of zircon and its role in petrogenesis, focusing on analytical techniques and the significance of trace elements. Zircon's saturation, crystallization, and zoning are discussed, along with the influence of melt composition and temperature. The chapter also examines the major and trace element compositions of igneous zircon, including Hf, REE, P, U, and Th, and their implications for petrogenetic processes. The text highlights the importance of trace element zoning, such as oscillatory and sector zoning, in understanding zircon's petrogenetic history. Additionally, it discusses the REE patterns and anomalies (Ce and Eu) in zircon, which provide insights into the oxidation state and petrogenetic conditions of the host rocks. The chapter concludes by discussing other trace elements in zircon, such as U, Th, and Pb, and their significance in geochronology and geochemical studies.