This technical report presents mineral processing information for the Dikulushi open pit cutback project in the Democratic Republic of Congo, based on historical operating data and metallurgical testwork.
Report context
The Dikulushi Open Pit Project, owned by Mawson West Limited through its subsidiary CMCC SARL, is located in the Katanga Province of the Democratic Republic of Congo, approximately 50 km north-northwest of Kilwa on the southwestern side of Lake Mweru. The technical report is dated September 16, 2011 and addresses the planned open pit cutback extension of the existing Dikulushi pit previously operated by Anvil Mining Limited. The project is at an advanced stage, with a pre-feasibility study completed to determine the economics of developing the Dikulushi deposit via an open pit cutback.
Processing route
Plant flowsheet
The Dikulushi plant flowsheet is shown in Figure 17.1 of the technical report. The float plant at Dikulushi operated from 2004 to 2008, fed with high grade ore from the open pit and underground mine. The plant produced a copper concentrate using conventional flotation methods. Tailings storage facilities are addressed separately in the report.
Metallurgical testwork by Anvil Mining
Several metallurgical testwork programmes were completed by Anvil on the Dikulushi ore. Early testwork was conducted, followed by later testwork. These results are considered appropriate for deposits with similar styles of mineralisation, such as Dikulushi, and have subsequently been compared against actual production results during the period of operation by Anvil.
The most recent metallurgical testwork was managed by Sedgman Metals, a metallurgical consulting company of Perth, Western Australia. Testwork was completed at AMDEL Laboratories in Perth.
Additional testwork was reported on in June 2004 by Independent Metallurgical Laboratories (IML) utilising samples provided from the mill feed and an open pit sample to perform a locked cycle flotation test. Results indicated from a feed grade of 8.76% copper and 306 g/t silver that a recovery of 91.1% copper and 89.7% silver could be achieved to produce a concentrate grade of 42.1% copper and 1,447 g/t silver. This sample contained 18% acid soluble copper in feed.
Metallurgical testwork details
Testwork details from the report include drillcore used in Mintek metallurgical testing, with details presented in Table 13.1. Head grades of chalcocite composites are shown in Tables 13.2 and 13.10. The relative abundance of significant minerals is presented in Table 13.3.
Comminution testwork results are shown in Table 13.4. Flotation testwork examined the effect of grind size on flotation performance for high grade chalcocite (Table 13.5), disseminated and low grade chalcocite (Table 13.7), and lead/zinc rich chalcocite (Table 13.9). The effects of collector addition on flotation performance were tested for high grade chalcocite (Table 13.6) and disseminated and low grade chalcocite (Table 13.8). The effect of grind size and Eh level on flotation performance for lead/zinc rich chalcocite is shown in Table 13.9. Locked cycle flotation test results are presented in Table 13.11.
Historical plant operational results
Actual production results during operation by Anvil showed recoveries of 93% copper and 90% silver, producing a concentrate with 55% copper and 2,100 g/t silver. A Dikulushi processing summary for the period February 2007 to April 2008 is presented in Table 13.12. Table 17.1 provides a Dikulushi Processing Summary relevant to ore to be mined in the pit cutback. Processing statistics for the low grade (LG) material completed by MWL are shown in Table 17.2.
Metallurgical properties of the cutback ore
There has been no change in the material ore types since the previous open pit and underground operations. It is therefore expected that the recoveries previously experienced for the fresh ore from the open pit will be achieved. The financial model uses a 90% recovery for both copper and silver, with a copper concentrate of 50% copper.
Key reported parameters
| Parameter | Unit | Design / Testwork Value | Operating Data |
|---|---|---|---|
| Copper recovery (flotation) | % | 91.1 (testwork), 90 (financial model) | 93 (historical operation) |
| Silver recovery (flotation) | % | 89.7 (testwork), 90 (financial model) | 90 (historical operation) |
| Copper concentrate grade | % Cu | 42.1 (testwork), 50 (financial model) | 55 (historical operation) |
| Silver concentrate grade | g/t Ag | 1,447 (testwork) | 2,100 (historical operation) |
| Acid soluble copper in feed | % | 18 (testwork sample) | Not specified |
| Feed grade (testwork sample) | % Cu | 8.76 | Not specified |
| Feed grade (testwork sample) | g/t Ag | 306 | Not specified |
| Processing period | years | Not applicable | 2004 to 2008 |
Project website: https://digbee.com/project/dikulushi
Technical qualifications
The principal source of information used to prepare this report is the information prepared for the development of the pre-feasibility study and the previously submitted NI 43-101 covering Mineral Resources at Dikulushi. This pre-feasibility information was provided to Optiro by MWL. The report presents technical information relevant to the Project's open pit cutback only.
The Qualified Persons have relied upon information provided by MWL relating to mining, legal, environmental and financial information. The Qualified Persons have not taken independent samples due to the operational nature of the respective resources and the visible in-situ mineralisation which confirms drillhole sample results.
Source: Technical Report on the Dikulushi Open Pit Project, Democratic Republic of Congo – September 16, 2011, Sections 1, 2, 13, 17, and associated tables and figures.
