Summary:
The Ruashi ore body is a stratiform, sediment-hosted copper deposit (“SSC”) located in the Central African Copper belt. The Copper belt forms one of the world’s greatest metallogenic provinces containing over a third of the world’s cobalt reserves and a tenth of the world’s copper reserves. The Central African Copper belt is second only to the Chilean Porphyry belt in terms of copper endowment but lags significantly in terms of production.
The Ruashi copper-cobalt ore bodies are situated within a 24 km long by 2 km wide, northwest to southeast trending fold structure. The Lukuni-Ruashi Etoile trend consists of a recumbent, synclinal fold, Ruashi on the southern limb and Etoille on the northern limb. The flanks are made up of Roan rocks and the core by the Mines Group, all occurring to the southwest of a prominent regional northwest to southeast trending thrust fault. A local thrust fault dipping to the south, locates within the RAT formation immediately south of the Ruashi ore bodies. A listric fault-breccia pattern separates the ore bodies from one another.
Three ore bodies have been identified at the Ruashi Mine, namely Ruashi I, Ruashi II and Ruashi III.
Ruashi I, the largest of the three, is located in the northwest of the mining area. The lateral extent of Ruashi I measures approximately 900 m in a northwest to southeast direction and 350 m across strike. In cross-section, the oxide zone extends to approximately 130 m below surface, whilst sulphide mineralisation has been intersected to depths of more than 300 m below surface. The Ruashi I ore body terminates against a brecciated shear zone on the north-western and south-eastern edges of the pit.
Ruashi II is a smaller fragment, extending along strike for approximately 200 m and 250 m across strike. It terminates against listric shear zones to the north-west and south-east. Currently, a flat lying thrust fault terminates the ore body in depth. Exploration is planned to confirm the lack of, or existence of a mineralised ore body below the thrust fault. A large gap of approximately 200 m of brecciated Lower Kundelungu strata separates Ruashi II from Ruashi I.
Ruashi III occurs at the south-easterly end and has a strike length of approximately 650 m and a cross strike width of 200 m. Unlike Ruashi I and II, the copper orebody is buried by 30 m to 80 m of cover rocks. A HG cobalt zone or “cap” with low grade copper starts at a depth of approximately 12 m below surface in the west. Ruashi III is structurally controlled within a complex fold structure. The oxide zone extends to a depth of 300 m in the east. Drilling during the latter part of 2010 exposed malachite mineralization some 200 m beyond the previous eastern limits of the ore-body, down to depths of 300 m. Artisanal mining on Ruashi III has not been as extensive as at Ruashi I and II, and was restricted to the upper near surface cobalt zone 10 to 20 m below surface.
Oxide copper minerals at Ruashi include malachite, chrysocolla, native copper, cuprite, cornetite and azurite. Other oxide minerals include magnetite and specularite. The dominant cobalt mineral in the oxide zone is heterogenite. Trace quantities of oxidised uranium minerals have been observed but are very uncommon.
Chalcopyrite and diginite dominate the copper minerals in the sulphide zone (up to 96%). Bornite is found in minor quantities. Cobalt sulphides in the form of linnaeite and carrollite are irregularly distributed in intimate mixtures with the copper sulphides, with sporadic abnormal concentrations. Extremely high quantities of cobalt may occur in veins dominated by cobalto-calcite. Disseminated pyrite is found in all the formations and occurs as small amorphous masses in the grey RAT (Roches Argileuses Talceuse).
Abundant pyrite mineralization occurs in the graphitic shales of the SDS zone. Chalcocite together with malachite occurs below the water table in the transition zone as replacement rims on primary bornite and chalcopyrite sulphides. Cobalt sulphides generally decrease with depth beyond the transition zone.
Production
In 2023, 17,274 tonnes of foreign ore were processed, a decrease by 84% compared to the 104,806 tonnes in 2022.
Ruashi started producing sulphide copper concentrate in 2023.
In 2023, Copper recovery rate for Cathode was 84.07% and 83% for sulphide copper concentrate.
| Commodity | Product | Units | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
|
Copper
|
Metal in concentrate
|
t
| ....  | | | | | | | | |
|
Copper
|
Concentrate
|
kt
| .... | | | | | | | | |
|
Copper
|
Cathode
|
t
| .... | .... | .... | .... | 33,824 | 24,108 | 31,546 | 32,129 | 35,056 |
|
Copper
|
Total
|
t
| .... | | | | | | | | |
|
Cobalt
|
Metal in hydroxide
|
t
| .... | .... | .... | .... | 5,070 | 4,752 | 4,638 | 3,391 | 4,344 |