Gem Diamonds’ Letšeng mine: pricing resilience and ore strategy for engineers
Reviewed by Joe Ashwell
First reported on MINING.com
30 Second Briefing
Gem Diamonds lifted average rough prices at its Letšeng mine to $1,395 per carat in H1 2026, as eight stones each selling for over $1 million generated $16.1 million despite a planned shift to lower‑grade ore in the Main Pipe. Standout recoveries included three diamonds above 100 carats and the 346.99‑carat Lesotho Jubilee, with a 52.24‑carat white stone achieving $32,908 per carat. Production will remain focused on the Main Pipe while the Satellite Pipe cutback is prepared, with margins hinging on continued premiums for large, high‑quality stones.
Technical Brief
- Letšeng ore routing in H1 2026 was deliberately biased to the lower-grade Main Pipe, reducing recovered carats despite slightly higher tonnes processed.
- Three +100‑carat stones were recovered, including the 346.99‑carat Lesotho Jubilee, scheduled for sale in H2 2026.
- Eight individual diamonds each cleared $1 million, together contributing $16.1 million of revenue from exceptional stones.
- A 52.24‑carat white diamond achieved $32,908/ct, indicating extreme price sensitivity to colour, clarity and size at Letšeng.
- All operational and financial metrics at Letšeng reportedly tracked within 2026 guidance despite the grade downgrade in the mine plan.
- Production for the balance of 2026 will be sourced exclusively from the Main Pipe while the next Satellite Pipe cutback is engineered and prepared.
- Letšeng’s current mine plan effectively trades grade for value, relying on low-frequency, high-value recoveries to sustain margins.
- In contrast to smaller‑stone operations suspending output under lab‑grown price pressure, Letšeng’s niche in rare large diamonds remains commercially viable.
Our Take
Letšeng is one of the few African diamond assets in our database where value is consistently dominated by a small number of +100‑carat stones, so the eight high‑value diamonds here reinforce its status as a price‑per‑carat rather than volume‑driven operation.
The $80 million development prepayment facility linked to Rock Tech Lithium’s Georgia Lake project, and its separate seven‑year offtake with Transamine, highlight how downstream buyers are willing to pre‑fund critical minerals projects, a financing structure that has not yet emerged for diamond producers such as Gem Diamonds in our coverage.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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