Jwaneng Diamond Mine: a $6bn Race to 1,000 Metres Underground

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One diamond mine produces more value per tonne of rock than any other operation on Earth. That mine is now preparing to dig nearly a kilometre deeper underground, at a cost of roughly US$6 billion, to keep producing after its surface pit runs dry.

That is the challenge facing Jwaneng in Botswana, and as of September 2026 the work is already well advanced.

Underground development is roughly 8,000 metres into construction, and open-pit operations are scheduled to cease in the early 2030s. The gap between surface production winding down and underground production reaching full stride is the single most consequential risk window the global diamond market will face over the next decade.

Here is what matters about this project, laid out in the order that makes it comprehensible. You will come away understanding what Jwaneng actually is at the geological level, why moving underground is so technically difficult, how the transition is being sequenced to avoid a supply gap, and what a delay would mean for diamond availability worldwide.

The mine that makes other diamond mines look ordinary

Jwaneng is described across multiple independent sources as the highest-value diamond mine on the planet, measured by revenue per carat rather than raw volume. That status is difficult to overstate and nearly impossible to replicate anywhere else.

The mine is operated through Debswana, a joint venture between the government of Botswana and De Beers. That ownership structure matters: it means Jwaneng sits at the intersection of national economic priority and one of the diamond industry’s most powerful commercial players, giving the project both political backing and deep technical resourcing.

The production numbers explain why this is not a peripheral asset. In 2023, Jwaneng produced 13.3 million carats from 85 million tonnes of rock mined, according to reporting compiled by DiscoveryAlert in September 2026.

Set that against Botswana’s national output and the scale sharpens. The country produced 25.1 million carats in 2023, valued at US$3.28 billion, at an average of US$131 per carat across all its mines, according to Sunday Standard reporting from May 2025.

Jwaneng alone accounted for more than half of Botswana’s entire national diamond production in 2023, from a single site.

The year-on-year shift in national valuations is worth understanding, because it shows how volatile diamond pricing can be even for a top-tier producer.

Volume rose slightly, yet total value fell sharply as the average per-carat price dropped from US$192 to US$131. A mine-specific current per-carat figure for Jwaneng is not publicly available, though every source confirms it realises the highest value of any mine globally.

The pricing context behind those national valuation figures is partly explained by diamond stockpile pressure, with Botswana’s unsold inventory reaching crisis levels in 2026 as lab-grown competition suppressed rough diamond prices across the market.

What this tells you is that Jwaneng is a load-bearing pillar of the diamond supply chain, not a routine mining project. That baseline is what makes everything that follows significant.

Three pipes, one pit, and a bridging strategy called Cut-9

Jwaneng’s diamonds come from three distinct kimberlite pipes. A kimberlite pipe is a carrot-shaped column of volcanic rock that carried diamonds up from deep in the Earth, and its geometry dictates both how the open pit is shaped and how any future underground mine must be designed.

Jwaneng’s three-pipe cluster is itself a geological rarity, and kimberlite pipe geology explains why so few of these carrot-shaped volcanic conduits ever contain enough gem-quality diamonds to justify a mine, let alone one of Jwaneng’s scale.

The three pipes are the geological foundation of the entire operation:

• BK1 contributes to the combined ore body and shapes the open-pit geometry above and the underground layout below.
• BK2 adds to the resource base and its structure feeds into the confined caving design planned for depth.
• BK3 completes the three-pipe cluster that the underground project ultimately targets to around 1,000 metres.

For decades, surface mining did the work. The way you extend an open pit’s life is through a cutback, a pushback of the pit walls to reach ore the existing geometry cannot access. Cut-8 was exactly that, a pushback that kept surface production running while underground planning advanced in parallel.

Cut-9 is the follow-on, and it plays a specific strategic role. It carries a budget of approximately US$1.5-2 billion (reported by Vietnam.vn in February 2026, though not independently verified) and is expected to add up to 53 million carats (also unverified), extending mine life to at least 2035.

The surface-to-underground sequence is best understood as three deliberate stages:

1. Cut-8 extended open-pit life by pushing back the walls to access deeper surface ore.
2. Cut-9 extends surface production further, to at least 2035, pushing the pit cessation date outward.
3. Underground development ramps up during that extended window, so it does not have to hit full capacity the moment the pit closes.

Here is why that sequencing matters to you. Cut-9 is not simply extra production, it is the project’s primary insurance policy against a supply gap. By pushing the surface cessation date into the early 2030s while underground capacity builds, it effectively decouples the two phases so the handover overlaps rather than happening as an abrupt cliff.

What going underground actually means at 1,000 metres depth

Mining engineers describe Jwaneng’s shift from open pit to underground as one of the most technically demanding transitions of its kind ever attempted. Understanding why requires walking through each source of difficulty in turn.

The underground project unfolds in two phases. Phase 1 uses blasthole open stoping (BHOS) and sublevel retreat (SLR) to mine kimberlite wedges on the existing pit walls, still influenced by the open pit above. Phase 2 moves fully below the pit into confined ground, using sublevel caving (SLC) and block caving (BC), where the ore body is undercut and allowed to collapse under its own weight for extraction.

Four sources of complexity interlock here. First, mining three pipes to roughly 1,000 metres below surface multiplies stress and rock-mass variability well beyond a shallow single-pipe operation. Second, coordinating the two phases means a delay or instability in one can cascade into the other.

Third is ore drive stability, the challenge of keeping the underground access tunnels intact in a deep caving environment, which work by Alvarez et al. identifies as materially harder at these depths.

The fourth factor is where the economics become vivid. Research by Fuenzalida found that recovery is highly sensitive to crosscut spacing, the distance between the tunnels used to draw ore out.

Recovery falls by approximately 3-4% for every 3-metre increment in crosscut spacing, meaning small layout decisions translate directly into large absolute value losses at a mine this valuable.

At Jwaneng’s per-carat value, a 3-4% recovery deficit is not a rounding error. It is real money lost from a premium ore body, which is why every metre of design choice carries a measurable financial consequence.

Why numerical modelling is doing the heavy lifting

Before any of this infrastructure is physically committed, engineers are running the whole system through computer simulation. Dunn et al. describe the use of two modelling tools, FLAC3D and Abaqus, which simulate how rock behaves and how a cave propagates at depth.

These models test drive spacing, block-cave heights, and zones of influence in software before a single tunnel is cut. Sensitivity analyses were run not to eliminate uncertainty in rock-mass behaviour and fragmentation, but to bound it, to understand the range of outcomes before committing to a design.

The logic is straightforward. At Jwaneng’s depth and ore value, a design error discovered after construction is vastly more expensive to fix than extended modelling before the work begins.

The timeline, the capital, and what a delayed ramp-up would cost the market

The project has moved through a structured sequence of studies and approvals, each a checkpoint on the way to underground production. Laid out chronologically, the milestones show a deliberately paced pipeline:

1. Late 2023: Overall feasibility study completed, with the environmental assessment fast-tracked.
2. May 2024: Underground mine development commenced.
3. 2024: Phase 1 pre-feasibility study PFS-A completed, with PFS-B ongoing.
4. Early January 2025: Debswana board approved investment for a key development phase.
5. By August 2026: Approximately 8,000 metres of development completed.
6. Early 2027: Full feasibility study for Phase 1 mining anticipated to begin.
7. Early 2030s: Open-pit operations scheduled to cease.

The capital stack has two distinct components that should not be confused. The underground project carries a most-recent estimate of approximately US$6 billion (DiscoveryAlert, September 2026), covering the deep mine build. That is separate from the US$1.5-2 billion Cut-9 open-pit cutback, which funds surface extension rather than underground construction.

The commercial stakes for the Jwaneng transition extend well beyond Botswana’s national budget, with De Beers’ financial position under acute pressure after reporting a historic loss in 2026, making the underground project’s capital certainty even more consequential for the joint venture.

Several mitigation measures underpin the transition’s resilience against a hard production gap:

• Early feasibility completion in late 2023, well ahead of the early-2030s cessation.
• Early mine development from May 2024, so infrastructure is built in time.
• Board-level investment approval, providing funding certainty.
• Cut-9 as the production bridge, decoupling surface cessation from underground ramp-up.

What a delayed ramp-up would actually mean for diamond supply

Here is where the risk needs careful framing, because the honest answer sits between two views that both hold truth.

The concerned view is straightforward. If underground ramp-up lags when the pit closes, the supply of top-quality premium gem stones tightens, because no other mine on Earth replicates Jwaneng’s per-carat value profile. That would squeeze the high end of the market and weaken De Beers’ and Debswana’s value contribution.

The more optimistic view points to resilience across the wider producer base. Russia’s Alrosa remained a top global producer in 2023 even under sanctions, which shows that total world diamond volume is spread across multiple large producers and does not collapse if one mine stumbles.

Both are correct, and that is the key insight. A delayed Jwaneng ramp-up is most likely to create a premium-segment quality constraint rather than a wholesale volume shortage.

The premium diamond price outlook beyond 2026 turns significantly on whether supply discipline from producers like Debswana can offset what some analysts characterise as structural demand erosion rather than a cyclical trough.

What this means for you as someone watching diamond markets, De Beers, or luxury supply chains is that the real vulnerability sits at the top of the gem-quality spectrum. Volume statistics alone will not capture it.

What the next decade looks like for Jwaneng and the diamond market

Pull the threads together and a clearer picture emerges. With development already underway, board investment approved, and Cut-9 extending the surface bridge to at least 2035, the project carries far more structural protection against a hard production gap than it did at the feasibility stage.

That does not make the outcome certain. Two watch points carry the most weight for anyone following this story:

• Early 2027: The Phase 1 full feasibility study begins, setting the engineering and financial parameters for the most critical transition period.
• Early 2030s: The rate of underground ramp-up relative to open-pit wind-down, the window where a gap would actually materialise if one occurs.

The early 2027 feasibility study is the next concrete signal the market receives about whether the transition is on track. Watch it as the key near-term milestone.

Return to where this started. Jwaneng is not a mine facing an ordinary end-of-life decision. Its ultimate destination is a confined underground operation reaching roughly 1,000 metres down, and how well that transition is executed will shape the premium tier of the global diamond market for a generation.

This article is for informational purposes only and should not be considered financial advice. Investors should conduct their own research and consult with financial professionals before making investment decisions. Past performance does not guarantee future results, and several figures cited remain unverified or subject to change based on project developments.