Why South Africa has diamonds

Why is South Africa so rich in diamonds?

Because it sits on the Kaapvaal craton, an old, thick-rooted core of continent, and kimberlite eruptions brought diamonds up from beneath it.

GIA explains the mechanism. Diamonds form 150 to 700 km down in the mantle. Kimberlite magma rises from those depths fast enough to carry them up without turning them to graphite, and kimberlites occur only beneath cratons, the ancient cores of continents with deep roots. South African diamonds come from the mantle beneath the Kaapvaal craton and are between 1 and more than 3 billion years old.

Erosion then did the rest. Diamonds weathered out of the pipes were carried by rivers, which is why the first South African finds were alluvial, in river gravels, before anyone knew what a kimberlite pipe was (Mining for Schools).

What is kimberlite, and where are the diamond pipes?

Kimberlite is the volcanic rock that carries diamonds up. It is named after Kimberley, where the first pipes were mined; the Cullinan pipe east of Pretoria is another.

Miners called it blue ground for its grey-blue colour. A pipe is a vertical, carrot-shaped body of it. At Cullinan the pipe is about 860 by 400 m at surface and covers 32 ha, narrowing with depth (SAIMM). About 300 m of the original pipe has already eroded away.

You can see one from the rim: the Big Hole lookout at Cullinan stands over the open pit mined into its pipe. Is the Cullinan mine still active? has the depths.

How did the South African diamond rush start?

With the Eureka, found in 1867 by 15-year-old Erasmus Jacobs near Hopetown. The 83.5-carat Star of South Africa followed in 1869, and in 1871 came the finds that made Kimberley.

The 1871 discoveries became the De Beers Mine and the Kimberley Mine, the hole that grew into Kimberley's Big Hole (source). Rival claims and companies were merged until, on 12 March 1888, De Beers Consolidated Mines was founded, with Cecil Rhodes as chairman. Mining at Kimberley stopped when the First World War broke out in 1914, and the Big Hole never reopened.

Cullinan came later. The Premier Mine was registered in 1902, and the Cullinan Diamond turned up there in 1905: the full story is in the Cullinan Diamond history.

Does De Beers own 90% of the world's diamonds?

No, not today. De Beers controlled roughly 80 to 85% of rough diamond distribution for most of the 20th century, but its share was about a quarter by 2021.

The 90% figure is history. De Beers' share of rough sales, from Wikipedia:

De Beers is itself changing hands. Anglo American owns 85% and Botswana 15%, and Anglo has been trying to sell its stake since 2024. In July 2026 Engineering News reported talks with a consortium led by former De Beers chief executive Gareth Penny, with no deal guaranteed. De Beers sold the Cullinan mine to a Petra-led group back in 2008.

What happens if you find a diamond in South Africa?

The Diamonds Act states that you must take it straight to the nearest police station. Keeping an unpolished diamond without a licence or permit is prohibited.

Two sections of the Diamonds Act 56 of 1986 cover it. Section 18 prohibits possessing an unpolished diamond unless an exception applies, such as a licence or permit. Section 25 states that anyone who finds one by chance must forthwith take it to the nearest police station and hand it to a SAPS member of the rank of sergeant or higher. The Act may have been amended since, and this is not legal advice.

On the mine tour you won't be tempted: a group visiting in 2025 was told not to pick up any rocks (source).

Is it cheaper to buy diamonds in South Africa?

There is no proof that it is. What is certain: foreign visitors can claim back the 15% VAT on goods worth more than R250 in total, taken out of the country within 90 days of the invoice.

The SARS VAT refund scheme for tourists is run by the VAT Refund Administrator, with desks at OR Tambo, Cape Town and King Shaka airports. Keep the original tax invoice, and present yourself and the goods to Customs when you leave; the R250 minimum is the total bought on one visit.

Beyond that, compare like with like. Ask for a grading report from a recognised laboratory and compare it with the same grade at home before you decide a price is good. The tour ends at a jewellery shop, the village has the Diamond Hub, and the mine and diamond shop day adds visits to local diamond dealers. None of them obliges you to buy.

The mine, a walk through Cullinan village and a visit to local diamond dealers, with transport from Johannesburg.

New · 6 hours · from $182

Explore the mine and diamond shop day → Tour details

What is the biggest or richest diamond mine in the world?

By value, Jwaneng in Botswana is described as the richest. Cullinan is not the biggest by output; it is famous for large and blue stones.

Mining.com called Jwaneng the richest diamond mine in the world by value in 2019; Debswana, a 50/50 venture of De Beers and Botswana's government, runs it. Rankings by carats differ and change, with Russian mines and Botswana's Orapa usually near the top.

Cullinan produces about 1.4 million carats a year, modest by those standards. Its record is in the big stones: more than 750 over 100 carats, and the largest gem-quality rough ever found. See the famous diamonds guide.

Can visitors see a diamond mine in South Africa?

Yes. Cullinan, east of Pretoria, runs surface tours of a working mine, and Kimberley's Big Hole is a historic site.

Cullinan is the one where diamonds are still being mined. The tour shows the shafts, a replica diamond room and the Big Hole lookout, over a pit South African Tourism describes as about three times the size of Kimberley's. Underground visits stopped in 2023: the underground tour guide explains.

From Johannesburg or Pretoria it makes an easy day; the day trip guide covers the route and the tours with pickup.

A working diamond mine on foot: the film, the shafts, the replica room and the Big Hole lookout, about two hours.

★ 4.6 · 2 hours · from $12

Explore the surface walking tour → Tour details

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