The Mg-suite and the highland crust: An unsolved enigma

Most of the rocks returned from the highlands are polymict breccias, pulverized by the massive bombardment. However, some monomict breccias with low siderophile element contents are considered to be 'pristine' rocks that represent the original igneous components making up the highland crust. Three principal pristine constituents make up the lunar highland crust: ferroan anorthosites, the Mg-suite, and KREEP. A discussion of these three constituents is presented.