The Namoya Project lies on the western edge of the Kibaran Mobile Belt (KMB). The KMB is an intercontinental mobile belt which was formed during the Mesoproterozoic between 1.4Ga and 0.9Ga when the supercontinent Rodinia was formed. The KMB is also known as a metallogenic province.

The Namoya Project, even though segmented into separate prospects, boasts one type of gold mineralisation style. The following deposit characteristics have been noted:-
-gold mineralisation hosted within quartz veins and quartz stockworks, striking in a northwestsoutheast direction;

- prevalence of tourmaline crystals within the quartz veins;

- deformation structures within the quartz veins, resulting in irregular sheets, nested vein sets, ladder veins and micro-veinlets, characteristic of shearing;

- no granitic intrusions in the immediate area of the Namoya orebody (as a possible source of tourmaline) although quartz porphyry intrusions have been intersected by drill holes at Namoya Summit and Muviringu signifying potential for a deep seated granitic body; and

- sericite/chlorite schists, sometimes with carbonates, indicative of a magmatic and hydrothermal processes.

The deposit characteristics are typical of the intrusion-related, tungsten/tin-associated type. This class of magmatic-hydrothermal deposits occurs within magmatic provinces best known for tungsten and/or tin mineralization. This type of deposit contains a metal suite that includes some combination of bismuth, tungsten, arsenic, tin, molybdenum, tellurium and antimony and contrasts with that found in more widely-developed goldrich porphyry copper deposits.

Mining operations are based on conventional drill and blast, load and haul mining techniques. Ore is drilled and blasted, and loaded by hydraulic excavators in backhoe configuration, with off highway dump trucks.

Excess RoM is stockpiled on the ROM pad, with low grade ore sent to the low grade stockpile, located approximately 400m from the RoM pad. Stockpiled RoM ore is sorted under a stockpile grade control management scheme, with stockpile reclaim undertaken by a front end loader, and then fed to the crusher as required. Waste material mined is hauled to close-by waste dumps.

Namoya process plant makes use of a hybrid leach design in which a heap leach operation works in conjunction with a gravity gold recovery operation and a CIL plant.

ROM, delivered by 40t trucks, is deposited into a tipping bin fitted with an 800mm static grizzly to prevent oversize material from entering the system. A rock breaker has been installed to ensure that all +800mm feed ore is broken to -800mm size, in line with process specifications. From the tipping bin, the ore is fed onto a 150mm vibrating grizzly using an apron feeder from which the -800+150mm material is deposited into a jaw crusher, which reduces the -800+150mm material to a topsize of 210mm. The resulting -210mm material from the jaw crusher, together with the -150mm from the vibrating grizzly, is conveyed along a 1.5km conveyor belt to the secondary crushing plant.

The -210mm material from the primary crushing plant is deposited onto the primary crushing stockpile whose residence time is 12 hours. The stockpile serves to provide backup plant feed against conveyor length surge and maintenance requirements of the primary crusher. The stockpile has two sets of reciprocating plate feeders (2 running, 2 on standby) which are designed to handle wet clay material as well as assist prevention of “rat holing” in the stockpile.

The objective of the gravity recovery section is to recover gravity-recoverable gold from the - 2mm size fraction. Feed material is pumped from the secondary and crushing circuit to a dewatering cyclone. The cyclone underflow then reports to one of two Knelson concentrators. The resulting concentrate reports to the gold room whilst the gravity tailings report to a desliming cyclone cutting at 150µm. The cyclone underflow (-2mm+150µm) gravitates to a dewatering screen from where the coarse (oversize) fraction reports to the heap leach pad. The -150µm fraction from the desliming cyclone, together with the undersize from the dewatering cyclone, report to a vibrating trash screen cutting at 800µm. The screen underflow is fed to a thickener feed tank where flocculant is added. The resulting mixture is then discharged into a 23m diameter thickener. The thickener underflow is collected and pumped to the CIL section.

Material is fed onto the heap leach in a controlled manner through the use of a crusher product stockpile. Vibrating feeders are used to withdraw material from this stockpile onto a conveyor belt which feeds the stockpile through the use of a grasshopper stacking system. Unslaked lime is added onto the conveyor belt and deposited onto the heap leach pad together with the ore.

The heap leach pad, measuring 600m x 800m, is designed on a 150 day leaching cycle. The pad consists of a series of cells that are irrigated with cyanide solution. As the solution passes through the heap, it dissolves gold into a cyanide complex which continues to drain, by gravity, through the heap for collection.

The heap leach pad has been designed to have three main solution ponds (barren solution, intermediate solution and pregnant solution). The barren solution pond holds barren cyanide which is then irrigated onto the heap. Because of the high rainfall in the project area, a wobbler solution irrigation system is used to assist with evaporation of excess solution in the system.

Pregnant solution is fed into the CIS columns. The columns, which are designed for a flow rate of 200m3 /hr, admit regenerated carbon through the top which gravitates to the bottom, loading gold onto its matrix in the process. Carbon moves through a series of CIS tanks in a countercurrent arrangement to the solution which gradually becomes barren as it moves downstream whilst the carbon loads more and more gold as it moves upstream. Loaded carbon is collected from the first tank and reports to the elution wash system whilst barren solution is collected from the last tank of the system and reports to the barren solution pond.

The CIL process consists of two tanks and is designed to leach the fine slurry for gold and load it onto the carbon. This system is essentially similar to the CIS system, with the main difference being that, in the CIL process, leaching takes places in the same vessels as carbon loading. The loaded carbon is collected and passed through a screen. The undersize from the screen is returned to the system whilst the oversize is collected and fed to the acid wash section. The tailings slurry exiting the CIL system is also passed over a screen from where the underflow reports to the tailings storage facility.

Loaded carbon is received from either the CIS carbon transfer or from the CIL loaded carbon screen and soaked for 1 hour in dilute (3%) acid. This process ensures the removal of inorganic salts containing calcium, iron and nickel. After the soak process, the residual acid is drained back to the acid make-up tank and a wash water cycle the takes place with the intention of removing any residual acid in the loaded carbon. Washed loaded carbon then gravitates to the elution column for gold recovery.

The elution circuit is based on the Zadra elution principle and operates at a temperature of 125°C. A higher temperature ensures a faster and more efficient stripping process of gold into solution. Acid washed carbon is fed into the elution column. The process commences with a pre-heating step during which eluent (cyanide and caustic) are heated to a temperature of 110°C for two hours. The heated eluent is passed through a primary heat exchanger before being admitted into the elution column.

During this process, the eluate emanating from the elution step is introduced into two electrowinning cells and a current is passed through the solution. During this process, gold ions dissolved in solution will precipitate onto the cathodes as a sludge leaving behind a barren solution that gravitates back elution circuit for reuse. After every two weeks, a cell is taken offline and the cathode removed and washed into the sludge tank filter. The filtered sludge then reports to the gold room for smelting.