Industry & supply chain

The trade calls the route from mine to consumer the pipeline. Upstream, mining companies extract rough and sort it into assortments by size, shape, color and quality, then sell it by term contract, tender or auction to dealers and manufacturers. Rough trading concentrates in Antwerp and Dubai, with producer-country sales in Gaborone.

In the midstream, manufacturers plan, cut and polish the stones. Bain and the Antwerp World Diamond Centre reported that India took about 90% of net rough diamond imports in 2019, most of it worked in Surat. Polished goods then move through bourses and dealer networks in Mumbai, Antwerp, Ramat Gan, Hong Kong, Dubai and New York, usually with laboratory grading reports attached.

Downstream, jewelry manufacturers set the stones and supply retailers, from luxury houses to chain stores and online sellers. Value rises at each stage, and so does the number of hands: smaller stones are traded in mixed parcels, sometimes several times, before they are set. Colored gemstones follow a looser version of the same chain, with more artisanal supply, few large producers, and hubs such as Bangkok, Chanthaburi, Jaipur and Colombo.

De Beers is owned 85% by Anglo American and 15% by the government of Botswana. Anglo American says it is committed to selling the company, and at its 2026 half year De Beers reported that a formal sales process was still running. Alrosa, owned by the Russian state, accounts for more than 90% of Russian diamond production. The United States sanctioned it in April 2022 and the European Union listed it in January 2024.

Rio Tinto took its last Argyle production on 3 November 2020, after 37 years and more than 865 million carats, and Diavik delivered its final production on 26 March 2026, with closure work running to 2029. Petra Diamonds cleans, sorts and sells its South African goods in South Africa and Antwerp. Lucara Diamond owns the Karowe mine in Botswana outright and plans to begin underground mining in the first quarter of 2028. Gemfields holds 75% of Kagem in Zambia, where the state Industrial Development Corporation holds the balance, and 75% of Montepuez in Mozambique, where Mwiriti Limitada holds the balance; it agreed in August 2025 to sell the Fabergé brand for US$50 million.

De Beers sells about 90% of its rough by value through Global Sightholder Sales. Sightholders are manufacturers and dealers with term supply contracts who buy boxes of sorted rough at sales events called sights, held ten times a year in Botswana, Namibia and South Africa. De Beers sets the assortments and the prices, and the sights themselves take place in Gaborone, Windhoek and Johannesburg. The rest of the production goes through De Beers Group Auctions, which runs an online platform from Gaborone and sells to buyers outside the sightholder list as well as to sightholders.

A tender is a sealed-bid sale. Petra Diamonds shows parcels for four to six working days in South Africa and Antwerp, takes one confidential electronic bid on each parcel, and awards it to the highest bidder. Producers often tender exceptional single stones on their own.

Gemfields applies the same method to colored stones. It has graded and auctioned Kagem emeralds since its first sale in July 2009 and Montepuez rubies since June 2014; by 2026 the ruby auctions had raised US$1.2 billion across 26 sales.

A diamond bourse is a members-only exchange where dealers trade rough and polished stones in person, usually in a secure building that combines a trading hall with offices, vaults, customs officers and bank branches. Dealers must be admitted as members, or attend as guests of members, and they are bound by the bourse’s rules.

The World Federation of Diamond Bourses (WFDB) held its first meeting in Antwerp in July 1947 and lists 27 affiliated bourses. Members undertake to settle disputes between members of different bourses by agreement or by arbitration. In 1978 the World Diamond Congress in Ramat Gan approved the IDC International Rules for Grading Diamonds, drawn up with the International Diamond Manufacturers Association.

Four of the 27 bourses sit in Antwerp. The Bharat Diamond Bourse has occupied Mumbai’s Bandra Kurla Complex since 2010 and has more than 4,000 members trading rough and polished goods. The Israel Diamond Exchange in Ramat Gan counts about 3,000 members and runs two trading halls, one for rough and one for polished, covering roughly 2,500 m².

Cutters and dealers hold large inventories for long periods. A manufacturer usually pays for rough promptly, spends weeks or months planning and polishing it, and then sells on credit or on memo, a consignment arrangement in which the buyer pays only if the goods sell. Barak Richman’s 2017 study of New York dealers describes a market in which merchants hold hundreds of thousands of dollars of another dealer’s stones on a verbal commitment. Banks bridge the gap with working-capital loans secured on inventory and receivables. Bain and the Antwerp World Diamond Centre put outstanding midstream debt at about US$11 billion in 2019, some 30% below the 2013 level, with operating margins in cutting and polishing at or below breakeven that year.

Two episodes made lenders warier. KBC decided on 19 September 2014 to run down Antwerp Diamond Bank, a specialist lender, after China’s Yinren Group failed to satisfy the National Bank of Belgium. In February 2018 the Reserve Bank of India put the Punjab National Bank fraud, worked through letters of undertaking, at US$1.77 billion. The English High Court later recorded losses of over £700 million in the extradition case against the jeweler Nirav Modi, held at HMP Wandsworth since March 2019.

Antwerp’s diamond industry dates itself to 1447. Its district beside the Central Station holds four of the world’s 27 bourses and the Antwerp World Diamond Centre, and about 1,300 companies employing roughly 3,300 people handled more than 72,000 shipments and 213 million carats there in 2025. Surat, in Gujarat, is where most Indian rough is cut; the Surat Diamond Bourse was inaugurated on 17 December 2023, and Mumbai remains India’s trading and export center.

Ramat Gan, beside Tel Aviv, holds the Israel Diamond Exchange. In New York, the district on 47th Street between Fifth Avenue and Avenue of the Americas is organized around the Diamond Dealers Club, whose roughly 1,800 members handled more than 95% of the diamonds imported into the United States according to a 2009 law review study. The Dubai Diamond Exchange sits inside the DMCC free zone, which recorded US$41.7 billion of diamond trade in 2025 against US$38.3 billion in 2023 and calls itself the largest platform for diamond tenders. Hong Kong serves Asia as a polished and jewelry market and hosts the HKTDC Hong Kong International Jewellery Show each March, which drew 2,353 exhibitors and 51,054 buyers in 2026.

Colored gemstones follow a different map. Thailand supplied about 70% of world polished sapphire exports and 90% of polished ruby exports in 2010, and Bangkok remains its trading base. Chanthaburi, southeast of the capital, was the world’s main ruby source from the early 1960s to the 1990s; its Friday and Saturday market now draws dealers carrying rough and cut stones from Mozambique, Tanzania, Nigeria and Madagascar, and local workshops heat and finish them.

Jaipur in Rajasthan employs roughly 150,000 people in colored stones, and GIA researchers reported in 2016 that about 90% of Gemfields auction lots are cut there. Sri Lanka’s trade runs through the dealer markets of Ratnapura and Beruwala, while Colombo holds precision lapidaries, the Sea Street jewelry workshops and the main retailers.

Idar-Oberstein in western Germany has cut agate and other chalcedony for more than 500 years, using sandstone wheels turned by water from the Nahe and nearby streams. Local deposits were largely worked out by the middle of the 19th century, after which its workshops imported rough from Brazil. It remains Europe’s main colored-stone processing town. Geneva plays a different part: Sotheby’s holds its Magnificent Jewels and Noble Jewels sales in the city.

Diamond dealing still rests on reputation. A deal is closed with a handshake and the phrase mazal u’bracha, Hebrew and Yiddish for luck and blessing, which the Israeli Diamond Institute describes as the trade’s standard way of sealing a sale. Under club by-laws an oral agreement made in the set words binds both parties, and a member who backs out can be taken before an arbitration board. Barak Richman’s study of the New York Diamond Dealers Club records that a dealer who ignores an award has his photograph posted in the central trading hall and circulated to bourses abroad. That sanction bites harder than a court order, because diamonds are portable, hard to trace and easy to sell anywhere.

The trade grew through family and community networks. Richman found that Diamond Dealers Club members came mostly from observant Jewish communities and worked in family firms whose earnings depended on a shared reputation, so that entry usually ran through relatives. Ownership has passed the same way at the top of the industry. The Oppenheimer family agreed in November 2011 to sell its 40% of De Beers to Anglo American for US$5.1 billion, which took Anglo American’s holding to 85%.

At the top of the market a few groups own the houses that combine design, sourcing and brand. Cartier and Van Cleef & Arpels belong to Compagnie Financière Richemont, a Swiss group registered in Geneva. LVMH owns Bulgari, founded in 1884, and Tiffany & Co., whose purchase it completed on 7 January 2021. Harry Winston, founded in 1932, went to the Swatch Group in 2013 for US$750 million plus up to US$250 million of net debt. Graff bought the 1,109 ct Lesedi La Rona rough from Lucara in September 2017 for US$53 million, or US$47,777 per carat.

Online retailers sell loose diamonds from large virtual inventories, usually listing a grading report and magnified images for each stone, and set them in rings to order. Blue Nile and James Allen are the best-known names. Both belong to Signet Jewelers, which bought James Allen’s parent R2Net for US$328 million in August 2017 and Blue Nile for US$360 million in August 2022. Blue Nile also runs showrooms, 21 of them in the United States when Signet bought it.