Santa Fe is a zoned ultramafic intrusion of the Ipora Group of about 45 km2, emplaced in Precambrian granites and gneisses and Devonian sandstones and conglomerates. A large core consists of serpentinized dunite, together with peridotite, wehrlite and olivine clinopyroxenite. The dunites contain a little pyroxene and 5-10% opaques. Malignite and missourite are subordinate rock types, the latter comprising diopside/augite (50-60%), leucite (15-20%), olivine (10-15%) and biotite (5-10%), and some apatite and opaques, while the malignites consist of poikilitic orthoclase, nepheline, diopside/augite, biotite, apatite and opaques. A metamorphic aureole extends up to 500 m from the contact. Dykes of peralkaline quartz syenite occur containing 30-50% aegirine. Zones of vermiculitization occur within the dunites and peridotite.