Exploration for mineral deposits by chemically analyzing sampled rock, soil, vegetation, and other natural materials for trace amounts of the principal and associated elements. By now, most of the easily discovered mineral deposits have been found, making the search for new deposits ever more challenging. In spite of this, worldwide demands are rising for energy, metallic, and nonmetallic mineral resources. Search continues in regions of known mineralization and in areas where deposits are covered by sediment or obscured by vegetation and ice. Geochemical techniques have become an important part of almost all exploration programs.