Pronounced positive and negative geophysical anomalies on EVERARD represent the crystalline Musgrave Block in the north, a basement trough more than 4 km in depth that flanks the Musgrave Block to the south, and the crystalline Ammaroodinna Inlier to the south-east of the basement trough. Major faults separate these structural zones. Granulite and upper amphibolite grade metamorphic rocks of early Adelaidean age which were folded about north-east and east-trending axes have been intruded by a jointed granite pluton having K/Ar and Rb/Sr ages of approximately 1100 Ma and 1150 Ma respectively. Gabbroic dykes have intruded both the metamorphic rocks and the granite pluton, and commonly follow the joints in the latter. Together, these crystalline rocks comprise the Musgrave Block on EVERARD. Greenschist grade rocks having K/Ar and Rb/Sr ages of approximately 1100 Ma and 1000-1050 Ma respectively form the fault emplaced Ammaroodinna Inlier. A middle Adelaidean succession of folded but unmetamorphosed clastic, glacigene, carbonate and basic volcanic rocks (mainly Umberatana Group equivalents) abuts the Musgrave Block along a faulted contact. Folding of this succession has occurred about east-trending axes (Indulkanan Folding) except where it has been controlled by movements of the basement margins. Overlying the Adelaidean succession with marked angular unconformity is the gently folded (Chandleran Movement) arenaceous sequence of the Palaeozoic Officer Basin. An unconformity is inferred between the Lower Palaeozoic "Marla and Munda sequences" and the younger Palaeozoic Mintabie Beds and Waitoona Beds. Thin, flat lying Mesozoic sedimentary deposits in the eastern part of EVERARD are marginal remnants of the Great Artesian Basin, and have been gently domed and faulted. Recent aeolian and alluvial sediments blanket much of the area. Groundwater is the most important economic mineral on EVERARD, precious opal has been mined intermittently, and hydrocarbons may yet be proved to occur in the Palaeozoic Officer Basin.