The main rock types in the mine area are bimodal mafic and felsic volcanics rocks of the West Kahama segment of the Nyanzian age Kahama Greenstone Belt. The mafic rocks are predominantly flows, overlain by a series of felsic pyroclastics and ash tuffs. Argillites occur within the mafic flows and at the mafic/felsic contact and are the principal host for the mineralization. Mafic dykes/sills, commonly lensoid along their northwest strike, are a significant part of the lithological package southwest of the deposit itself. The Bukoli Granite, which separates the Kahama belt from the Rwamagaza belt to the west, lies approximately 3 km southwest of the mine. Together with regional faults, the Bukoli Granite forms the bounds of a rhomboid-shaped greenstone domain at Bulyanhulu.

The gold mineralization, together with copper sulphides and silver, occurs in quartz veins localized along steeply-dipping structures parallel to the regional northwest strike. Nine of these extensive quartz vein systems have been discovered so far with Reef 1, hosted by a shear zone developed preferentially along the most extensive sedimentary unit, the most significant. The ore is characterized by sub continuous lenses and veins of black quartz concentrated in narrow shear zones. An initial stage of syn-depositional barren clastic pyrite has been identified, overprinted by a polymetallic hydrothermal event associated with gold and copper mineralization. Alteration, dominantly carbonatization with the major introduction of Fe, Ca, As, Zn and S, is largely restricted to <5 m around the mineralized quartz veins. Initial fluid inclusion studies suggest the mineralizing fluid was carbonic and methane-bearing at 300-450C.

In the second half of 2017 Acacia took the decision to place Bulyanhulu on reduced operations due to the inability to export gold concentrate. Following the transition to reduced operations in Q4 2017 Bulyanhulu is running on tailings.

Underground production successfully restarted at Bulyanhulu in Q4 2020, with the plant recommencing processing of underground ore.

Bulyanhulu mine utilizes a long hole stoping method.

Mineralization is associated with steeply-dipping reefs containing gold, silver and copper in sulphides.

The following processes are utilised: Crushing, Grinding, Gravity, Flotation, Carbon-In-Leach, Thickening, Cyanide destruction, Filtration and Paste Backfill.

The feed ore to the Plant from the underground operations contained gold, silver and copper. The feed grade is between 6.5 – 10.0 g/t of gold and 0.3 – 0.5% of copper. The sulphide minerals are mainly pyrite (FeS2) and chalcopyrite (CuFeS2). The Plant is recovered these valuables using gravity and flotation processes. Free milling gold and electrum particles are recovered using gravity techniques and intensive cyanide leaching reaction followed by electro-winning to produce doré bars.

The primary cyclone overflow is sent to rougher flotation from where the tailings are thickened and disposed of to the tailings dam or as backfill. The rougher concentrate is classified to produce a cyclone overflow which went to four stage re-circulating concentrate cleaner cells.

The first stage cleaner tail is cle ........