The Morila orebody is hosted within an interpreted metamorphosed impure arkose and feldspathic arenite (formerly recorded as metagreywacke), a metamorphic rock dominated by quartz, plagioclase, biotite and alkali feldspar. X-ray diffraction and petrology studies indicate a near uniformity of gangue (silicate) mineralogy throughout the sequence, extending several hundred metres beyond the proposed final pit depth.

According to Reynolds, “the gold mineralization is hydrothermal in origin and is contained within altered metasediments close to the contact with intrusive tonalite. Alteration is commonly silica-feldspar alteration as well as minor argillic alteration. The visible sulphide mineralization consists of arsenopyrite, pyrrhotite, pyrite and trace chalcopyrite. Coarse visible gold is a common occurrence” The south eastern portion of the Morila pit incorporates a portion of a tonalite intrusive which is also uniform in composition, consisting of plagioclase, quartz and biotite with minor chlorite and amphibole.

The main pit has been mined via open pit. Currently no active open pit mining occurs, production is primarily retreatment of tailings and dumps.

Closure of operations at Morila was originally scheduled for 2013 but, together with the Pit 4S pushback, completed in 2015, the Domba satellite deposit and the re-tailings treatment projects, processing of the marginal ore and mineralized waste should extend its life to 2019.

Run-of-Mine (ROM) ore is transported directly from the open pit in 90 tonne payload, CAT 777D haul trucks. This material is either stockpiled on the ROM pad or directly tipped into the primary crusher. The Nordberg-54/75 primary crusher reduces the ore down to less than approximately 300 millimetres in a single stage, open circuit.

The crushed product is withdrawn from the primary crusher by an apron feeder and conveyed along conveyor 01-CVR-01 to the inplant, crushed ore stockpile. The live capacity of the stockpile is approximately 10,000 tonnes.

Crushed material is withdrawn from the in-plant stockpile via three apron feeders situated below the stockpile. Ore is conveyed from the apron feeders to the SAG mill by conveyor 02-CVR-01. The ore is milled in a 6 MW, semi-autogenous grinding (SAG) mill in open circuit. The pulp exits the mill over a trommel screen.

Oversize from the trommel screen is crushed in a pebble crusher and is returned back to the SAG mill. Trommel undersize is pumped from the mill sump to the cyclone cluster for classification. The coarse undersize exiting the cyclone is returned to a single 6 MW, secondary ball mill operating in closed circuit. The pulp discharging the ball mill is combined in a common (to the SAG mill) discharge sump.

Three centrifugal gravity concentrators operating in parallel recover coarse gold, post screening at two millimetres, from a bleed stream of the cyclone underflow. Gravity concentrate is redressed in the gold room over a Gemeni table. An Intensive Leach Reactor is integral to the gravity circuit. The cyclone overflow material passes over a linear screen for tramp removal prior to being thickened in a 35 metre diameter highrate thickener. Clarified water is returned to the circuit for re-use in the metallurgical process.

Thickener underflow in the form of thickened pulp is pumped to the carbon-in-leach (CIL) circuit to be leached with cyanide as the lixiviant in seven 2,500 m3 mechanically agitated tanks. The barren tailings material discharged from the last CIL tank is screened and pumped to the tailings storage facility (TSF).

Loaded carbon is acid treated prior to elution. The resultant pregnant solution following the twelve tonne Anglo American Research Laboratories (AARL) elution is subject to electrowinning. Gold is electrowon from pregnant electrolyte onto stainless steel cathodes. The cathode sludge as well as redressed gravity concentrate is then calcined and smelted separately into gold doré.