Letšeng Diamond Mine

The Letšeng kimberlites are unique and have been a source of intrigue for geologists since their discovery. Not only are the diamond populations atypical, but the way the pipes were formed, and their emplacement history is unusual. Several features of the two Letšeng pipes (Main and Satellite) differentiate them from the Kimberly-type Pyroclastic Kimberlites and impact our understanding of the complex distribution of diamonds within the pipes.

Following the publication of Letšeng’s 2015 SAMREC Mineral Resource and Reserve Statement, efforts were focused on improving confidence in the geological models and the predictability of the large +100 carat Type II diamonds, which contribute materially to Letšeng’s value.

Initial petrography and microdiamond studies in the latter part of 2015 suggested that the geological complexity in both the Main and Satellite pipes may have been greater than that reflected in the broader resource categories at the time. What started as an exercise to better understand the internal variability of the existing resource domains in Main pipe (KMain, K6 and K4) and Satellite pipe (NVK and SVK), transformed into a comprehensive drilling and resource development programme spanning eight years and culminating in a new appreciation of the complexity within the Letšeng orebodies, as now reflected in the 2024 Resource and Reserve Statement contained in the NI 43-101 Technical Report.

The 2024 Mineral Resource and Reserve Statement was prepared following the Canadian Institute of Mining, Metallurgy and Petroleum’s (CIM) Estimation of Mineral Resources and Mineral Reserves Best Practice Guidelines dated November 2019, and the Definition Standards for Mineral Resources and Mineral Reserves published May 2014, and are reported in accordance with the Canadian Securities Administrators’ National Instrument 43-101 Standards of Disclosure for Mineral Projects.

Letšeng’s 2024 Mineral Resource Statement is informed by a suite of geological studies that (i) enabled differentiation between the various known and newly recognised kimberlite domains, (ii) delineated the internal boundaries between the kimberlite domains and (iii) characterised these domains in terms of their diamond populations, volumes, tonnages, grades and value.

The 2024 Resource and Reserve Statement and NI 43-101 Technical Report is based on an extensive drilling and resource development programme that commenced in 2015 and was completed in 2023 and included the following workstreams:

• Three phases of diamond core drilling: 2017-2020 (31 drillholes, 8 386 metres), 2021-2022 (24 drillholes, 8 640 metres) and 2022-2023 (8 drillholes, 2 235 metres);
• Petrographic analysis and mineral chemistry conducted between 2015 and 2023 in both the Satellite and Main pipes;
• Microdiamond analysis: initial studies in late 2015 followed by more detailed studies in 2019-2020;
• Discrete sampling, production and updated sales data was analysed for diamonds recovered from the dominant domains within each pipe;
• In-pit mapping data of internal and external domain contacts;
• 3D geological models for both the Satellite and Main pipes were updated;
• Updated the Size Frequency Distributions for each domain; and
• As-built survey of the open-pit topography as of 31 December 2023.

The NI 43-101 Technical Report containing the 2024 Resource and Reserve Statement for Letšeng is available here.

Letšeng Mineral Resource Statement (effective date of 31 December 2023)

(Note: the tables and accompanying notes below are presented as a direct extraction from the NI 43-101 Technical Report)

Modifying factors were applied to the Indicated Resource to develop an open pit mine plan, extracting the economically viable ore domains from both Main and Satellite pipes. The Reserve has been prepared on a Life-of-Mine plan which includes final open-pit cutbacks at current slope angles in the Satellite and Main pits, SC6W and MC4W respectively. The life of the open pits is estimated at 13 years from the effective date of the Reserve estimate. Main pipe contributes 76.1% and Satellite pipe contributes 22.2% of the estimated Reserves, whilst the remaining 1.7% comes from ore stockpiles on surface. All Mineral Reserves are classified as Probable.

Letšeng Mineral Reserve Statement (effective date of 31 December 2023)

Ghaghoo Diamond Mine

Since mid-2013, the geological team at Letšeng has been working with a team of leading kimberlite experts from Canada and South Africa to gain a deeper understanding of the relationships between the various kimberlite types within each pipe and to differentiate the higher grade varieties from those with high value (containing large and abundant Type II diamonds).

Owing to the decline in prices for the Ghaghoo diamonds, it became apparent that the sustainability of the mine, in its current form, was not financially viable. No further resource evaluation work was carried out at Ghaghoo during the commissioning and ramp-up phases before the decision was taken to place the mine on care and maintenance. Consequently, there has been no update to the Resource and Reserve statement published by Venmyn Deloitte in 2014.