major division of rocks and time in southern Africa in Precambrian Time (3.96 billion to 540 million years ago). The system consists of a great thickness of sedimentary and metamorphic (altered) rocks with numerous intrusions of igneous bodies. Two major subdivisions of the Swaziland System are recognized, an Upper and a Lower series. Many of the units that constitute the Swaziland System contain mineral deposits of great value, including gold, copper, and uranium—a circumstance that has spurred intensive study and exploitation.