The gold mineralisation is entirely restricted to the intensely silicified rocks which form the core of these deposits. The silica core of each system is enveloped by argillic alteration that is zoned from an inner alunite-kaolinite. This argillic zone is usually less than 1 to 10 m thick. The silica zone is underlain by deep alteration characterised by abundant pyrite and typically Na rich alunite, while dickite dominates over kaolinite. At depth the alunite dickite grades into a sericite-chlorite assemblage.
The principal ore minerals are enargite and electrum, with rare luzonite in the upper sections and ubiquitous and dominant pyrite throughout. Gold grades, which are intimately associated with goethite as native gold in the upper parts of the orebody, are roughly concentric, decreasing outwards.