Lucara Diamond Corp. says its Feasibility Level study (FS) for a potential underground operation at the Karowe Diamond Mine, is on track for release in H2, 2019. The company said in an update that the Board of Directors have approved a budget of US$14.8 million to complete the technical programme and the FS study in 2019. Drilling is expected to be completed toward the end of Q1 2019 with logging, data collection, and the receipt of laboratory results expected toward mid Q2 2019. Completion of the FS study and final reporting is expected in late H2 2019, it added.
Lucara CEO, Eira Thomas said, “Finally, we are delighted to be welcoming Gord Doerksen and JDS to the feasibility team to direct the study and provide Lucara with a fit for purpose underground mine design that will work to optimise and maximise the economic returns of the underground project. The feasibility study will be completed by in the second half of 2019″.
In 2018, following the release of a positive Preliminary Economic Assessment the company embarked on a US$29 million technical programe to support a FS for a potential underground operation at the Karowe Diamond Mine, with the aim of extending mine-life from 2026 to at least 2036.
The programme included a mineral resource update, geotechnical drilling of the country rock and AK06 kimberlite, hydrogeological drilling and modelling, and mining trade off studies to address risks and issues identified during the PEA. A total of US$23 million was spent out of a 2018 budget of US$29 million in support of this work and resulted in significant de-risking of the key technical components associated with the potential underground development.
According to the company, updated resource model in Q2 2018 showed that indicated resources increased by 54% in the South Lobe and confirms increased contribution of EM/PK(S), a higher grade, higher value ore unit, with depth
The new base of the Indicated Mineral Resource is at 400 masl (600 metres below surface). Modifications to the internal geological model for the South Lobe of the AK06 kimberlite resulted in the recognition of the EM/PK(S) unit as the volumetrically dominant unit at depth within the South Lobe. With 75% of the South Lobe Indicated recoverable carats between 600 and 400 masl being attributed to the EM/PK(S) unit.
“The updated mineral resource completed in 2018 highlighted the important contribution of the higher grade, higher value EM/PK(S) geological unit as we mine deeper in the south lobe and has necessarily re-focused our approach to the Karowe Underground study. Historically, we now know that the EM/PK(S) has produced some of Karowe’s most valuable diamonds, including the 1,109 carat Lesedi La Rona and the 813 carat Constellation,” said Thomas.
The company also revealed that mining method selection is being considered in accordance with the geotechnical and hydrogeological interpretations and technical data already collected and in progress. At present 4 possible alternatives are being studied. These include variants on block cave with shaft access, sub-level retreat / sub-level cave with access via a decline, and conventional vertical crater retreat stoping followed by block cave via shaft access. As greater clarity on the rock mass and geotechnical characteristics of the host rocks and units internal to the South Lobe become available a final decision will be made for the most appropriate mining method.
“In 2019 we will be evaluating various mining scenarios that have the potential to access this valuable ore as early as possible in the underground mining schedule. Other highlights from our 2018 work program included the successful completion of a deep hydrogeological drilling campaign, which did not encounter significant water and has substantially de-risked the overall underground project,” she added.
Lucara added that it continues to engage in discussions with the Government of Botswana to extend the mining lease to include underground mining operations. In support of these discussions Lucara is updating the Mine Closure Plan, closure cost estimates, the Environmental Management Plan, as well as the Social Economic Impact Assessment.