Modern Mining March 2019

feature DIAMOND MINING One of the open pits at Letšeng.

Letšeng sets new records

– which has a workforce of over 2 000 people – mines ore from two pipes, the Main pipe of 17,0 ha and a Satellite pipe of 5,2 ha. During 2018, Letšeng reduced its waste tonnes mined by 3,9 million to 25,8 million tonnes. This reduction was achieved through improved drilling and blasting techniques enabling the incorporation of a number of Business Transformation initiatives, most notably the steeper inter-ramp slope angles. This steepening has resulted in significantly lower life of mine (LoM) stripping ratios while increasing and bringing forward the ore ton- nage mined from the higher-value Satellite pipe, considerably increasing the mine’s LoM net present value (NPV). Tonnes treated during 2018 increased to 6,5 million, of which Letšeng’s plants treated 5,4 million (2017: 5,3 million), with the remaining 1,1 Mt being treated by Alluvial Ventures (AV), a third party contractor (2017: 1,1 million). The contract with AV has been extended to mid-2020. The contribution from the higher-value Satellite pipe material increased by 3 % to 2,2 Mt. Of the total ore treated, 61 % was sourced from the Main pipe, 33 % from the Satellite pipe and 6 % from the Main pipe stockpiles. Both Letšeng plants were stopped during May for planned major maintenance work, adversely affecting the availability of the plants during H1-2018. The planned replacement of the scrubber shell in Plant 2 was completed on schedule. However, an unexpected and significant repair to its concrete foundation delayed the shutdown by 10 days. The impact of this additional downtime was mitigated by the temporary installation of a scrubber bypass conveyor. Following this extensive maintenance and the enhanced efficiencies resulting from vari- ous Business Transformation initiatives, the plant runtime improved. This resulted in a significant increase in the tonnage treated dur- ing H2-2018. Overall grade for 2018 was 1,94 cpht, due in part to the Business Transformation initiative to re-treat tailings material through a mobile XRT sorting machine. This machine recovered 11 905 carats in 2018, of which 6 233 related to historical (pre-2018) tailings material. As mentioned, Letšeng recovered a record number of diamonds greater than 100 carats during 2018, the biggest being the 910-carat

The Letšeng diamond mine of LSE-listed Gem Diamonds in Lesotho recovered a record 15 diamonds greater than 100 carats in 2018, including the 910-carat ‘Lesotho Legend’, as well as a record number of diamonds greater than 20 carats. Overall, the mine produced 126 875 carats over the year (compared to 111 811 in 2017), with the average value achieved being US$2 131 per carat, a 10 % improvement over 2017.

R evenue for 2018 (Gem’s financial year coincides with the calendar year) was US$267,3 million com- pared to US$214,3 million in 2017, delivering a profit of US$46,6 mil- lion, well up on the figure of US$20,8 million (before exceptional items) recorded in 2017. Earnings per share rose from 6,56 US cents be- fore exceptional items in 2017 to 18,80 cents in 2018. In 2017 Gem launched a Business Trans­ formation programme with the aim of achieving US$100 million in incremental revenue, pro- ductivity improvements and cost savings by the end of 2021. The latest results indicate good progress towards achieving this goal. Situated in the Maluti mountains, Letšeng

36  MODERN MINING  March 2019