Layering within both the host and ore is absent. Ores commonly contain inclusions of anorthosite indicating they are younger. Cataclastic fabrics present in the anorthosites and gabbros, but lacking in the ores are thought to indicate the ore mineralization has migrated to its present location by some tectonic process. The host rock is generally a medium grained, anorthosite with the plagioclase andesine to labradorite in composition. With addition of pyroxene local gradations to gabbro are present.
Ore minerals consist of magnetite, ilmenite, hematite, ulvospinel and rutile.
Apatite is a common accessory as are nickel and copper sulfides. Some anorthosite complexes are surrounded by zones of charnokite, a peculiar pyroxene-rich anhydrous metamorphic rock. If is thought to form by dehydration of metasediments with accompanying iron addition from the magmatic fluids. The presence of coexisting oxide phases has permitted the use of phase diagrams to fix temperatures of crystallization. This presents a problem for theories of crystallization for these ores which favor magmatic segregation with settling of the denser oxides to the base of the anorthosite complex.