Iron-rich hematitc beds, hematitic pisolites and thick kaolin strata frequentely occur within the upper portion of the LCZ. The LCZ is comprised predominantly of variegated clay, which may be white, violet, blue, reddish brown, grey or green-grey in colour. Surface exposures extend discontinuously over a distance of approximately 25km a long south western margin of the bauxite outcrops in the south zone. The upper part of the LCZ exhibits similar pisolitic textures to the BXZ, which change with increasing depth to bauxitic clays, Kaolinitic clays, Kaolinised parent rock and finally unaltered parent rock. It is essentially the transition zone between Bxz and the Parent rock Sequence. The lower clay is characterized by by the gradational reduction with the depth in the intensity of bauxitisation. The Biyadh Formation comprises primarily fine- grained, well-bedded sandstone (15cm 20cm thick) with either a kaolinitic, hematitic or siliceous matrix. The exposed thickness of the Biyadh Sandstone is approximately 5m. The sandstone outcrops are frequently associated with rough, rocky desert, hammadah, chaotic heaps of flat, platy blocks, or steep, rocky hills. The Biyadh Sandstone outcrops along the south western portion of the south zone area, striking NW-SE over a distance of approximately 3km to 11km North West of the village of Al Bi'ithah. The unevenly eroded bauxite assemblage (Lower Clay Zone, Bauxite Zone, Upper Clay Zone) is overlain by the Wasia Formation (Upper Cretaceous) and Aruma Limestone on the north eastern limb of the deposit.
The Biyadh Sandstone (Lower Cretaceous) represents the oldest rock formation, outcropping south west of the bauxite outcrops. It comprises of three main zones, South zone, Central zone and the North zone, with each zone being approximately 30 km long. The deposit has an overall strike length of approximately 105 km, trending in occurs a Northwest- Southeast direction, and an identified width of 5 km.
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