Diamond Mining and Value

Where diamonds are found

Natural diamonds form about 150 to 200 kilometers down in the mantle, under the oldest and thickest parts of the continents. They reach the surface in rare, fast volcanic eruptions that leave carrot-shaped pipes of a rock called kimberlite (and, less often, lamproite). Most kimberlites carry few or no diamonds, which is why a new diamond mine is a rare event.

Geologists split deposits into two kinds. Primary deposits are the pipes themselves, mined from the top down. Secondary deposits form when erosion washes diamonds out of old pipes into rivers, beaches and the seabed. Alluvial diamonds in West and Central Africa and the marine deposits off Namibia are secondary. The US Geological Survey lists southern Africa, Australia, Canada and Russia as holding the major reserves (USGS Mineral Commodity Summaries, February 2026).

How a diamond mine works

Most large diamond mines start as open pits on a kimberlite pipe. As the pit deepens and the walls get too steep or too costly to push back, the operation usually moves underground, often by block caving beneath the old pit. Alluvial operations dig and screen river gravels, from small hand-worked pits to large earth-moving fleets, and marine mining uses ships that lift gravel from the seabed.

Extracting diamonds from ore is mostly a sorting problem. The USGS notes that most ore bodies hold from less than 1 carat to about 6 carats per ton of rock, so a plant may handle millions of tons to recover a few hundred kilograms of diamonds. The usual steps are:

1. Crushing, set coarse enough to avoid breaking large stones.
2. Scrubbing and screening to remove clay and fines.
3. Dense media separation, where heavy minerals, diamonds included, sink in a dense slurry and lighter rock floats off.
4. Final recovery with X-ray sorters (diamonds fluoresce under X-rays) and, at some plants, grease tables, because diamonds repel water and stick to grease.

Our articles on raw diamond ore and how it is processed and on rough diamond types pick up from there.

The biggest producers, mines and companies

By volume, Russia is the largest producer. The USGS estimates it mined about 21 million carats of gem-quality diamonds in 2025, roughly 30% of world output, with Angola, Botswana and Canada at around 13 million carats each. Value tells a different story, because the quality and size of stones differ a lot between mines. Botswana’s Jwaneng is often described as the richest diamond mine by value.

Source: USGS Mineral Commodity Summaries 2026, gemstones (excludes industrial diamond).

A small group of diamond mining companies has long accounted for most of the world’s rough supply, De Beers, ALROSA and Rio Tinto among them. Russian rough and polished diamonds are under sanctions in the US, the EU and other G7 countries. For rankings, see the biggest diamond companies and the biggest diamond mines in the world.

The diamond mining market today

The natural diamond market has been in a downturn since early 2023, according to the USGS. Weaker jewelry sales left cutters and traders holding stock, which cut demand for rough diamonds and pushed rough prices down, with the strongest effect on stones of one carat or less. Laboratory-grown diamonds, which have the same chemistry and structure as mined stones at a lower price, have taken a growing share of that lower end. Larger, rarer stones and colored diamonds have behaved differently. Our comparison of lab-grown and earth-mined diamonds goes into the trade-offs. Since 2003, international trade in rough diamonds has run through the Kimberley Process certification scheme, which was set up to keep conflict diamonds out of the supply chain.

Diamond exploration and buying a mine

Diamond exploration usually starts with indicator minerals. Kimberlites carry distinctive garnets, chrome diopside, ilmenite and chromite that survive erosion, so geologists sample streams and soils and follow the trail back toward the source. Magnetic and gravity surveys then look for the round, pipe-shaped anomalies kimberlites tend to produce, and drilling tests the best ones. A pipe only becomes a mine after bulk sampling shows enough carats per ton, and enough value per carat, to pay for the plant.

If you are looking at diamond mines for sale, ask for the license documents, bulk sample results and an independent valuation of recovered parcels, and check how the stones would be exported under the Kimberley Process. Our diamond exploration case study from Botswana shows how satellite mineral detection ranks Exploration Targets across a license, to decide where sampling and drilling go first. It comes before a JORC or NI 43-101 resource estimate and does not replace one. If you just want to dig, Crater of Diamonds State Park in Arkansas lets visitors search a plowed field and keep what they find.