Vertical drillhole BCD1 intersects the ore zone and footwall rocks to a depth of 100 m. They contain at least one felsic unit and have been locally carbonated. There is a suggestion of hydrothermal alteration near the bottom of the hole where kaolinisation has taken place in the presence of fresh pyrite. Above this, pyrite is oxidised to goethite.
Feldspars weather progressively to kaolinite and amphiboles to smectite.
These rocks become upwardly friable and their foliation is cemented with clay, iron oxide and calcite. The ore zone lies mainly within phyllitic rocks which are variably kaolinised and ferruginised. Progressive ferruginisation has replaced both minerals and fabrics, leaving only relict muscovite and shard-like quartz. Vesicles are lined with goethite, which becomes progressively poorer in Al, hematite and several Mn minerals including cryptomelane and lithiophorite. The upper part of the weathered profile has been subjected to calcrete formation where the rocks have been brecciated and set in a complex carbonate cement.