Operational overview


Letšeng Diamond Mine


Ghaghoo Diamond Mine

Letšeng Diamond Mine

The Letšeng mine is located in the Maluti Mountains of Lesotho and is renowned for its recovery of large, high quality, exceptional Type II diamonds.

Among these diamonds recovered are the 910 carat “Lesotho Legend”, the 603 carat “Lesotho Promise”, the 550 carat “Letšeng Star” and the 493 carat “Letšeng Legacy”.

Letšeng has also produced high-quality pink and blue diamonds, with a rare blue diamond achieving a sales price of US$603 047 per carat in 2013 and an exceptional pink diamond achieving US$656 934 per carat in 2019.

Letšeng ranks in the top 10 global diamond producers by revenue. The large high value greater than 100 carat diamonds from Letšeng account for 70% to 80% of the Group’s revenue annually.

Letšeng has grown to be one of the largest open pit diamond mines in the world, processing ore from two kimberlite pipes, the Main pipe 17.0ha and the Satellite pipe 5.2ha. In 2017, certain Business Transformation initiatives were undertaken to unlock additional value at Letšeng, which included an updated open-pit life of mine plan, large diamond recovery and reduced diamond breakage initiative projects, and a mining optimisation project.

For more information on Letšeng, please refer to the latest:

Ghaghoo Diamond Mine

The Ghaghoo mine, situated near the south-eastern border of the Central Kalahari Game Reserve was acquired by Gem Diamonds in May 2007 with a 25-year mining licence obtained from January 2011. The mine consists of a 10.4ha kimberlite pipe, and has an in situ value of US$4.9 billion (as at 1 January 2014). Diamonds produced at Ghaghoo are of a commercial quality and lower value and size than those from Letšeng.

The Ghaghoo mine, the first underground diamond mine in Botswana, was placed on care and maintenance in 2017 following the weak state of the diamond market for the category of diamonds produced at Ghaghoo and a decision was made to proceed with the sale of the Ghaghoo mine.

During the first six months of 2018 a formal sale process to sell the Ghaghoo mine commenced with Nedbank Capital being appointed as the corporate advisor on the transaction. The sales process continues.

For more information on Ghaghoo, please refer to the latest:


Sales and Marketing

Gem Diamonds continues to invest in its sales, marketing and diamond analysis operations to pursue ways of maximising revenue through a combination of marketing channels, including tenders, strategic partnerships and extractions for manufacturing to capture additional margins further along the diamond pipeline.
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From Letšeng mine

The Letšeng mine produces large, exceptional quality diamonds which supply the very top end of the diamond market.

Letšeng’s top-quality diamonds are sent from Lesotho to Baobab Technologies in Antwerp for analysis to achieve the greatest returns at each of the diamond tenders.

Rough diamond analysis

Baobab Technologies

Baobab Technologies’ advanced mapping and analysis of Letšeng’s top-quality rough diamonds assists in assessing appropriate true values of these rough diamonds before they are presented for sale.

This in-depth knowledge provides the basis for setting robust reserve prices for each of the high value diamonds at each tender and assists in making strategic selling, partnering or manufacturing decisions.

Sales and marketing services

Gem Diamonds benefits from actively managing its own multi-channel marketing strategy and by establishing and developing relationships with new and existing clients.

Gem Diamonds maximises revenue from its rough diamonds through a combination of channels, which includes tenders and partnerships, in addition to pursuing additional initiatives further down the diamond pipeline.

Polished diamonds are sold through direct selling channels to prominent high-end diamantaires.


Gem Diamonds’ client base consists of prominent high end diamantaires and manufacturers from the world’s major diamond centers: Belgium, India, Hong Kong, Israel, New York and Dubai.


Resources and Reserves


Letšeng Diamond Mine


Ghaghoo Diamond Mine

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)

          Average Value  
Classification Pipe Domain Density
Contained Carats
Indicated Main K1A 2.52 7 109.6 1.56 2 170 110.9
RFW-K1S-K1AS 2.52 2 781.3 1.56 2 170 43.4
K1B-1 2.51 7 635.6 1.59 980 121.4
RFW-K1S-K1B-1s 2.51 2 417.2 1.59 980 38.4
K1B-2 2.51 5 177.2 1.59 980 82.3
RFW-K1S-K1B-2 2.51 74.4 1.59 980 1.2
K1C 2.51 959.2 1.59 980 15.3
K2 2.54 25 793.5 1.61 1 130 415.3
K6 2.48 5 682.1 2.47 825 140.3
Total Main 2.52 57 630.1 1.68 1 211 968.5
Satellite NVK 2.50 5 175.6 2.19 2 185 113.3
SVK 2.45 7 967.7 2.26 2 535 180.1
GVK 2.45 1 746.3 3.46 970 60.4
GVK-SVK Mixed 2.45 1 715.7 3.11 1 420 53.4
KIMB7 2.47 1 310.8 2.28 2 475 29.9
Total Satellite 2.47 17 916.1 2.44 2 088 437.1
TOTAL INDICATED 2.51 75 546.2 1.86 1 484 1 405.6
Inferred Main Pipe K1A 2.52 5 929.9 1.56 2 170 92.5
RFW-K1S-K1AS 2.52 122.0 1.56 2 170 1.9
K1B-1 2.51 7 152.9 1.59 980 113.7
RFW-K1S-K1B-1s 2.51 396.7 1.59 980 6.3
K1B-2 2.51 1 371.0 1.59 980 21.8
K1C 2.51 348.7 1.59 980 5.5
XENO-BSLT 2.66 1 154.9 0.40 1 130 4.6
K4 2.52 697.5 1.10 360 7.7
K6 2.48 4 952.6 2.47 825 122.3
Total Main 2.51 22 126.2 1.70 1 217 376.3
SVK 2.45 1 539.3 2.26 2 535 34.8
GVK 2.45 309.7 3.46 970 10.7
KIMB7 2.47 597.1 2.28 2 475 13.6
    Total Satellite 2.45 2 446.1 2.42 2 238 59.1
TOTAL INFERRED 2.51 24 572.3 1.77 1 356 435.4
1. The effective date of the Mineral Resource Statement is 31 December 2023. The QP for the estimate is Cliff Revering, P.Eng., an employee of SRK Consulting (Canada) Inc.
2. Mineral Resources are not Mineral Reserves and do not have demonstrated economic viability. All numbers have been rounded to reflect accuracy of the estimate.
3. Mineral Resources are inclusive of in-situ Mineral Reserves and are exclusive of all mine stockpile material.
4. Mineral Resources are quoted above a +2.00 mm square-mesh bottom cut-off and have been factored to account for diamond losses within the smaller sieve classes.
5. Inferred Mineral Resources are estimated on the basis of limited geological evidence and sampling, sufficient to imply but not verify geological grade and continuity. They have a lower level of confidence than that applied to an Indicated Mineral Resource and cannot be directly converted into a Mineral Reserve.
6. Average diamond value estimates are based on diamond sales data to the end of 2023 provided by Gem Diamonds Ltd.
7. Mineral Resources have been estimated with no allowance for mining dilution and mining recovery.

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)

Classification Pipe

Average Value
Contained Carats(kct)

Diamond Grade(cpht) Diamond Price(US/ct)
Probable Main K1A Grouping 9 450.1 1.55 2 170 146.5 317 888.3
K1B Grouping 14 790.2 1.58 980 233.6 228 910.4
K1C 935.0 1.57 980 14.7 14 392.6
K2 17 512.4 1.60 1 130 279.6 315 958.5
K6 5 250.8 2.48 825 130.2 107 432.2
Total Main 47 938.6 1.68 1 224 804.6 984 582.0
Satellite NVK 3 442.5 2.16 2 185 74.4 162 658.6
SVK 6 164.0 2.22 2 535 136.6 346 341.6
GVK 1 673.5 3.45 970 57.8 56 067.3
GVK-SVK Mixed 1 674.4 3.09 1 420 51.7 73 413.4
KIMB7 1 200.9 2.20 2 475 26.4 65 248.7
Total Satellite 14 155.5 2.45 2 028 346.9 703 729.6
Stockpile Live S/P 11.2 1.95 1 754 0.2 382.5
Main Pipe S/P 900.7 1.25 1 190 11.2 13 380.2
Satellite Pipe S/P 176.6 1.41 2 287 2.5 5 693.6
Total Stockpiles 1 088.5 1.28 1 394 14.0 19 456.3
TOTAL PROBABLE 63 182.5 1.84 1 465 1 165.5 1 707 767.9
1. The effective date of the Mineral Reserve Statement is 31 December 2023.  The QP for the estimate is Dr Anoush Ebrahimi P. Eng., an employee of SRK Consulting (Canada) Inc.
2. Figures have been rounded to the appropriate level of precision for reporting.
3. Due to rounding, some columns or rows may not compute exactly as shown.
4. Grades quoted as recovered and dry, pre-acid wash.
5. The Mineral Reserves are stated as in‐situ dry metric tonnes.
6. K1A Grouping includes K1A, RFW-K1S: K1AS and RFW-K1S: XENO-BSLT.
7. K1B Grouping includes K1B-1, RFW-K1S: K1B-1s, K1B-2 and RFW-K1S: K1B-2.
8. The Mineral Reserves were prepared under the guidelines of the CIM, for reporting under NI 43‐101.
9. Average diamond value estimates are based on diamond sales data to the end of 2023 provided by Gem Diamonds Ltd.
10. Modifying factors for mining recovery of 88% and waste dilution of 12% applied on pipe contact blocks.
11. Probable Mineral Reserves were derived from Indicated Mineral Resources.
12. Mineral Reserves are inclusive of Mineral Resources.
13. There are no known legal, political, environmental, or other risks that could materially affect the Probable Mineral Reserves.
14. Stockpiles comprise surface loose stocks of material including high-value, low-value and highly diluted kimberlite contact ore.  Stockpiles of low-value and highly diluted kimberlite contact ore will be processed at the end of life of open pit mining.
15. The Mineral Reserves reported in this table are attributable solely to the ore to be mined (and processed or stockpiled for later processing) from the open pit mining operations at Letšeng Mine


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.

Technology and Innovation


Diamond damage is ubiquitous among producers of larger high-value gem diamonds. Furthermore, the Letšeng mine has a unique diamond distribution with a significant portion of its revenue held in the +5mm fraction (greater than two carats).

The Group has been working to mitigate the impact of diamond damage on Letšeng’s production for many years. While incremental improvements have been achieved through optimising operating practices and various technological enhancements, tweaking conventional technology will not realise the step changes required to significantly reduce diamond damage.

The potential changes for significantly improving revenue through reducing diamond damage are:

  • the early identification of liberated diamonds;
  • identification of diamonds within kimberlite; and
  • a non-mechanical means of liberating these diamonds within kimberlite.

Gem Diamonds has made significant progress on the identification, validation and testing of technologies from various industries to complement its innovation drive of early detection and non-mechanical means of liberating diamonds.




Diamond detection

Gem Diamonds successfully validated the detection of diamonds within kimberlite using scanning technology in conjunction with proprietary imaging and sorting algorithms. Two types of technologies are under investigation with varying degrees of detection potential, scalability and investment required. The proof of concept plant construction at Letšeng has highlighted various impediments and opportunities that need to be addressed and considered to enhance the operation of the technology employed.

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