Mining & sourcing

Open-pit mining removes rock in benches from the surface downward. It is the usual first stage at a kimberlite pipe, the carrot-shaped volcanic body that carries diamonds up from the mantle. At Jwaneng in Botswana, Debswana is mining at about 452 m and expects the pit to reach 816 m by 2034. When a pit becomes too deep to widen economically, operators go underground. Petra Diamonds’ Cullinan mine in South Africa uses block caving, in which ore is undercut so that it collapses under its own weight into collection points, and De Beers moved its Venetia mine from open pit to underground working in the early 2020s.

Alluvial mining works gravels in which rivers or waves have concentrated heavy, durable gems, as in the gem gravels of Ratnapura in Sri Lanka or the river beds of eastern Sierra Leone. Marine mining extends the idea offshore: off southern Namibia, Debmarine Namibia’s vessels recover diamond gravels from water 90–140 m deep with seabed crawlers and large-diameter drills.

Artisanal and small-scale mining (ASM) uses hand tools or light machinery and is often informal. The World Bank counted more than 44 million people working directly in ASM across 80 countries in 2020. A 2018 review for the Intergovernmental Forum on Mining put the workforce at 40 million in 2017 and, drawing on World Bank estimates from 2013, credited ASM with about 20% of the world’s mined diamonds and about 80% of its sapphires.

Botswana is Africa’s leading producer by value. Debswana, a joint venture of the government and De Beers formed in 1969, runs Orapa (opened 1971), described as the largest diamond mine by area, and Jwaneng (1982), the richest by value. Lucara Diamond’s Karowe mine had yielded ten diamonds above 1,000 ct by July 2026. Kimberley Process data show Botswana’s output falling from 18.1 million carats in 2024 to 15.5 million in 2025, after production pauses at Debswana mines in a weak market.

South Africa’s modern industry began at Kimberley, where miners dug the Big Hole between 1871 and 1914. Cullinan, now owned by Petra Diamonds, produced the 3,106.75 ct Cullinan diamond in 1905 and is the only significant source of blue diamonds. In Namibia, marine operations supply more than three-quarters of production. Angola’s Catoca pipe is owned 59% by the state company Endiama; the other 41%, formerly held by the sanctioned Russian miner Alrosa, passed to an Omani investor in November 2024. Around Mbuji-Mayi in the Democratic Republic of the Congo, diggers work vast deposits once dominated by the state company MIBA. In Sierra Leone, the Koidu kimberlite mine halted in 2025 after a labor dispute, idling the country’s largest diamond company; national output fell from 573,983 carats in 2024 to 121,620 in 2025.

Russia is the largest producer by volume and value, with 31.5 million carats in 2025 out of a Kimberley Process world total of 98.8 million. Almost all of it comes from the state-controlled Alrosa, mainly in Yakutia (the Sakha Republic). The Mir pipe was mined as an open pit until 2001, and its underground mine flooded in 2017. Udachny, whose pit reached about 640 m, and Jubilee near Aikhal are major sources. The EU and other G7 members banned direct imports of Russian diamonds from 1 January 2024, then extended it to Russian stones polished elsewhere: 1.0 ct and up from March 2024, 0.5 ct and up from September 2024.

Canada’s industry grew from the 1991 discovery of diamond-bearing kimberlites at Lac de Gras in the Northwest Territories, and it is now winding down. Rio Tinto’s Diavik ended production in March 2026 after more than 150 million carats. Ekati, open since 1998, stopped mining on 14 July 2026, when a court placed its owners in receivership after a sale process found no buyer. It is in care and maintenance under the receiver, with no permanent closure declared by September 2026. De Beers’ Gahcho Kué, due to stop at the end of 2027, is the country’s last operating diamond mine.

Australia’s Argyle mine, in the Kimberley of Western Australia, opened in 1985 and closed on 3 November 2020. It had supplied more than 90% of the world’s pink and red diamonds.

Rubies and sapphires are both corundum, crystalline aluminum oxide colored by trace elements: chromium makes ruby red, and iron with titanium makes sapphire blue. Mogok, in Myanmar’s Mandalay Region, has supplied fine rubies for centuries, along with sapphire, spinel and peridot, mostly from small pits and hand panning. The town became a front line in Myanmar’s civil war: the Ta’ang National Liberation Army captured it in July 2024 and withdrew after a China-brokered ceasefire in October 2025.

Around Ratnapura in Sri Lanka, whose Sanskrit name means “city of gems”, miners dig pits 10–50 m deep, haul up gem gravel and wash it in pans so the heavy minerals settle. The island is best known for blue sapphire.

The Kashmir sapphire mines lie at about 4,500 m near Sumjam, in the Paddar area of Jammu and Kashmir. Found around 1881, they yielded their finest crystals between 1882 and 1887; later campaigns found little. Near Chanthaburi and Trat in eastern Thailand and at Pailin in western Cambodia, basalt-related gravels once produced ruby and sapphire in quantity, and Pailin’s gems helped finance the Khmer Rouge. Both areas are far less productive today, but Chanthaburi remains a major trading center.

Mozambique became a leading ruby source after deposits near Montepuez in Cabo Delgado province became widely known in 2009. Montepuez Ruby Mining, owned 75% by Gemfields and 25% by the Mozambican company Mwiriti, began mining in 2012 on a 33,600-hectare concession and sells its rough at auction. Madagascar’s Ilakaka rush followed the 1998 discovery of a large alluvial sapphire deposit; the new town’s population reached nearly 60,000 by 2005.

In Montana, sapphire was first found along the Missouri River in 1865. Yogo Gulch, mined from 1895, produces cornflower-blue sapphires colored evenly enough that they are not heat treated, unlike most sapphires on the market. Its major mines are inactive and hobby miners work the area. The state’s most productive deposit is Rock Creek, whose stones, like those from the Missouri River, are routinely heated.

In central Queensland, the Anakie gemfields around the towns of Sapphire, Rubyvale and Anakie have yielded sapphire from alluvial wash for more than a century and remain open to licensed fossickers as well as small commercial miners.

Colombia has set the standard for emerald since the Spanish conquest. The Muisca mined emeralds before the Spanish arrived; conquistadors reached Chivor in 1537 and the Muzo area in the 1540s. Muzo, Coscuez and Chivor, all in Boyacá department, remain the main districts. Colombia supplied about 47% of world emerald output in the decade to 2005, a share that has since declined.

Zambia ranks second. Kagem, an open pit in the Ndola Rural Emerald Restricted Area of the Copperbelt, is owned 75% by Gemfields and 25% by the state Industrial Development Corporation, and Gemfields calls it the world’s single largest producing emerald mine. Mining paused on 1 January 2025 after Zambia reimposed a 15% export duty, and resumed in May 2025 once the duty was suspended. It yielded an 11,685 ct crystal, named Imboo, in 2025. Gemfields has sold Kagem rough through its own auctions since 2009.

Brazil produces emerald from mica schists at Carnaíba in Bahia and in Minas Gerais. In Afghanistan’s Panjshir Valley, about 113 km northeast of Kabul, miners work at elevations of roughly 2,100–4,300 m, and the workings remain largely informal. Commercial production there began in the early 1980s. Ethiopia became a source in late 2016, when the first emeralds from the Shakiso area of the Oromia region reached international markets. The mines lie near the village of Kenticha and were dug by hand at first.

Tanzanite, the blue to violet variety of the mineral zoisite, is mined commercially only in the Merelani Hills of northern Tanzania, in a strip about 7 km long and 2 km wide. It was identified in 1967. After a 24 km wall was built around the mines to curb smuggling, recorded production rose from 147.7 kg in 2018 to 781.2 kg in 2019.

Minas Gerais in Brazil yields aquamarine, topaz and tourmaline in almost every color from granitic pegmatites, and Teófilo Otoni is its main gem-trading city. Copper-bearing “Paraíba” tourmaline, a vivid blue to green, reached the international gem market in 1989 from São José da Batalha in Paraíba state; similar material later came from Rio Grande do Norte, Nigeria and Mozambique.

Hpakant in Myanmar’s Kachin State is the principal source of jadeite. Loosely regulated mining there is deadly: a landslide of mine waste on 2 July 2020 killed more than 160 people. The Sar-e-Sang mines in Badakhshan, Afghanistan, supplied the ancient world with lapis lazuli, including stone found in Tutankhamun’s tomb. Turquoise has been mined for thousands of years in the hills about 50 km northwest of Nishapur in northeastern Iran. Australia dominates precious opal: black opal comes from Lightning Ridge in New South Wales, where the first shafts were sunk in 1905, and light opal from Coober Pedy in South Australia, where opal was found in 1915.

Diamond explorers hunt for kimberlite indicator minerals: grains of garnet, chrome diopside and ilmenite whose chemistry shows they formed at mantle depths and which rivers or glaciers spread away from a pipe. Aeromagnetic, resistivity and gravity surveys then locate the pipe, and drilling and bulk sampling test its grade, in carats per hundred tonnes, and the value of its diamonds. In 1991 Chuck Fipke and Stewart Blusson followed an indicator-mineral trail across the Northwest Territories to the Lac de Gras pipes that became Ekati, setting off a huge staking rush.

At the plant, ore is crushed and passed through dense media separation, in which a ferrosilicon slurry floats away light rock and keeps heavy minerals. Diamonds glow under X-rays, so luminescence sorters detect and eject them from the concentrate; earlier plants used grease belts, to which diamonds stick. X-ray transmission (XRT) sorting instead measures how much of a beam each particle absorbs. Diamond, made of light carbon atoms, absorbs less than the surrounding rock, so large stones can be pulled out before crushers break them. In April 2015 Lucara commissioned an XRT section of five TOMRA sorting streams at Karowe to treat material from 8 to 60 mm. It works alongside the dense media separation circuit, which kept the finer fraction. On 18 November 2015 it recovered a stone announced at 1,111 ct, later named Lesedi La Rona and recorded at 1,109 ct when Lucara sold it in September 2017.

Diamonds lifted Botswana from one of the world’s poorest countries at independence in 1966 to one of Africa’s wealthier economies, but they also concentrate risk. The sector supplied about 80% of exports from 2012 to 2023 and about two thirds in 2024. Mineral revenue, almost all of it from diamonds, fell from 13.3% of GDP in 2022 to 1.9% in 2024 and about 3.0% in 2025, against total revenue of 24.1%. The World Bank estimated that the economy contracted by 0.9% in 2025. The February 2025 agreement with De Beers extended Debswana’s mining licenses to 2054 and raised the share of output sold by the state-owned Okavango Diamond Company from 25% to 30% to 2030, then 40% to 2035 and 50% after that. It also pledged BWP 1 billion to a Diamonds for Development Fund.

Beneficiation policies aim to keep more of the value chain (sorting, cutting, polishing, trading and jewelry making) at home. They brought De Beers’ rough sales to Gaborone, where its sights have been held since 2013, and cutting workshops to Botswana, Namibia and South Africa, although most polishing still happens in India.

Sierra Leone shows the other side. Diamonds funded armed factions in the civil war of 1991–2002. Artisanal mining now employs an estimated 300,000–400,000 people and is hard to monitor. Since December 2001 the Diamond Area Community Development Fund has returned 0.75 percentage points of the 3% diamond export tax to mining chiefdoms.