A diamond does not simply appear in a jeweller's window. It travels thousands of kilometres, passes through dozens of hands, and is transformed at every stage. From the volcanic pipe where it formed over a billion years ago to the ring on someone's finger, the journey is longer, more intricate, and more human than most buyers realise.
Understanding the pipeline — the full chain of custody from extraction to retail — changes the way you evaluate a diamond. It explains why certain stones cost what they do, why provenance matters, and why the industry looks the way it does today.
Stage One: Mining
Every natural diamond begins underground. The stones form between 150 and 700 kilometres beneath the earth's surface, in conditions of extreme heat and pressure. They reach the surface through volcanic eruptions that create kimberlite and lamproite pipes — vertical columns of diamond-bearing rock that can be mined.
Primary Mining
Primary mining targets these pipes directly. The operation is industrial. Open-pit mines excavate the pipe from the surface until depth makes it uneconomical; then underground tunnels take over. Major kimberlite operations — Jwaneng in Botswana, Mirny in Siberia, Venetia in South Africa — produce millions of carats per year.
The largest producers in the world are De Beers (operating primarily in Botswana, Namibia, South Africa, and Canada), ALROSA (Russia), Rio Tinto (Australia and Canada), and Petra Diamonds (South Africa and Tanzania). Together, they account for the majority of global rough diamond supply.
Alluvial Mining
Not all diamonds remain in their host pipe. Erosion over millions of years carries stones into riverbeds, beaches, and ocean floors. Alluvial mining recovers these diamonds from secondary deposits — sometimes by hand in artisanal operations, sometimes by industrial dredging along coastlines.
Alluvial diamonds often have smoother surfaces and fewer inclusions, because the journey from pipe to riverbed acts as a natural sorting process. Stones that survived the tumbling tend to be structurally sound. Some of the world's most celebrated diamonds — including many historic Indian stones — were alluvial finds.
The Numbers
Global production fluctuates, but in a typical year the world's mines yield roughly 120 to 130 million carats of rough diamonds. Of these, only a fraction — perhaps 20 to 30 percent by volume — will be gem quality. The rest goes to industrial use: cutting, grinding, drilling. The distinction between gem and industrial is made at the next stage.
Stage Two: Sorting and Valuation
Rough diamonds look nothing like finished gems. They arrive from the mine as dull, irregularly shaped crystals — some as small as a grain of sand, others the size of a walnut. Before anything else happens, they must be sorted.
Sorting takes place at centralised facilities, often near the mine or in major trading hubs. De Beers sorts through its Global Sightholder Sales division; ALROSA through its sorting centre in Moscow. The process is methodical and highly skilled.
Each rough stone is classified by:
- Size — measured in carats, from melee (under 0.20 ct) to large stones of 10 carats or more
- Shape — the natural crystal form: octahedron, dodecahedron, macle, or irregular
- Colour — from colourless through the yellow and brown spectrum, with rare fancy colours separated out
- Clarity — the presence and severity of internal features visible under magnification
The Diamond Trading Company (DTC) historically used over 16,000 categories to classify rough. Each category carries a different price. The difference between an octahedral, near-colourless two-carat rough and an irregular, tinted stone of the same weight can be enormous — one might yield a beautiful engagement ring centre stone, the other a set of small accent diamonds.
Stage Three: Cutting and Polishing
This is where the diamond becomes recognisable. A rough crystal enters the cutting workshop; a finished gem emerges. The transformation requires planning, precision, and — despite modern technology — a great deal of human judgement.
The Major Cutting Centres
The world's diamond cutting is concentrated in a handful of cities, each with a distinct character:
Surat, India — processes roughly 90 percent of the world's diamonds by volume. Surat specialises in smaller stones, from melee up to about one carat, where speed and efficiency are paramount. The city's cutting industry employs hundreds of thousands of skilled workers.
Antwerp, Belgium — the historic heart of the diamond trade. Antwerp handles higher-value stones and remains the world's leading hub for rough diamond trading. Its cutting workshops focus on quality over volume. (Why Antwerp Matters)
Tel Aviv, Israel — known for expertise in fancy shapes and larger stones. Israeli cutters have a reputation for innovation, particularly in developing new faceting patterns.
New York, USA — a smaller cutting centre today, but still significant for high-value stones destined for the American market, particularly those above five carats.
The Process
Cutting a diamond follows a sequence that has been refined over centuries, though the tools have changed dramatically. (Diamond Cutting & Manufacturing Basics)
Planning — the cutter studies the rough crystal, often using 3D scanning technology, to determine the optimal shape and faceting pattern. The goal is to maximise a combination of weight retention, beauty, and value.
Cleaving or sawing — the rough is divided along its natural grain, either by cleaving (splitting along a crystal plane) or by laser sawing.
Bruting — the stone is given its basic outline shape. For a round brilliant, this means grinding two diamonds against each other to form the circular girdle.
Faceting — the cutter places each facet on a rotating polishing wheel, or scaife, using diamond-impregnated paste. A standard round brilliant has 57 or 58 facets, each angled to precise tolerances.
Final inspection — the finished stone is examined for symmetry, polish quality, and proportions. Stones destined for grading reports are sent to independent laboratories such as the GIA.
The weight loss from rough to polished is significant. A well-shaped octahedral crystal might yield a polished stone retaining 40 to 50 percent of its original weight. Less regular shapes can lose 60 percent or more. This is why the planning stage matters so profoundly — a few degrees of difference in a facet angle, a slightly different decision about where to saw, can mean thousands of dollars in value gained or lost.
Stage Four: Trading
Once cut and polished, diamonds enter the trading ecosystem — a network of dealers, brokers, and exchanges that connects cutters to retailers.
The Rough Market
Rough diamonds are sold through several channels:
Sights — De Beers sells rough to a select group of approximately 80 approved buyers, known as sightholders, at events held ten times per year in Gaborone, Botswana. Sightholders receive pre-assembled boxes of rough at prices set by De Beers. This system, which has evolved considerably since its inception, remains the primary distribution mechanism for De Beers production.
Tenders and auctions — producers like Rio Tinto and Petra Diamonds sell portions of their output through competitive tender, where qualified buyers bid on individual lots. Exceptional stones — large, rare, or unusually coloured — are often sold this way to capture their full market value.
Open market — rough diamonds also trade on the secondary market, where dealers buy and resell parcels. This market provides liquidity and allows smaller manufacturers access to supply.
The Polished Market
Polished diamonds trade through a separate but overlapping network:
Diamond bourses — exchanges in Antwerp, Ramat Gan (Israel), New York, and Mumbai where registered dealers meet to buy and sell. The World Federation of Diamond Bourses oversees 30 affiliated exchanges globally.
Online platforms — services like RapNet and virtual inventories have digitised much of the polished trade, allowing dealers to list and search for stones by specification.
Direct manufacturer-to-retailer — larger jewellery brands increasingly source directly from cutting houses, bypassing intermediary dealers to secure supply and control quality.
Pricing in the polished market is influenced by the Rapaport Price List, a benchmark published weekly that provides per-carat prices for round brilliant diamonds across a matrix of colour, clarity, and weight categories. Individual stones trade at premiums or discounts to "Rap" depending on cut quality, fluorescence, and other factors. (Pricing Basics)
Stage Five: Retail
The final stage brings the diamond to the consumer — through a wholesaler, a jeweller, or increasingly, an online retailer.
Wholesale to Retail
Most independent jewellers do not buy rough or deal on bourses. They purchase polished stones from wholesalers or through memorandum — a consignment arrangement where the jeweller holds diamonds on approval and pays only when a stone sells. This system reduces risk for retailers but adds another layer of margin to the chain.
Larger brands — Tiffany, Cartier, and others — operate vertically integrated supply chains, controlling sourcing, cutting, and retail under one roof. This vertical integration is a growing trend in the industry, driven by consumer demand for transparency and traceability.
The Jeweller's Bench
Once a diamond reaches the jeweller, it is set into a piece of jewellery by a master setter — a specialist who secures the stone in its mounting using techniques that have been practised for centuries. The setting must hold the diamond securely while allowing maximum light to enter and exit the stone. A well-executed setting is invisible; a poor one can diminish even an exceptional diamond.
The Consumer
The end buyer — whether choosing an engagement ring, a pair of earrings, or an investment stone — is the final link in a chain that may have taken two to three years from mine to purchase. The price they pay reflects every stage: the cost of extraction, the skill of the cutter, the margins of each intermediary, and the brand or retailer's positioning.
The Lab-Grown Parallel
Lab-grown diamonds follow a shorter, fundamentally different pipeline.
Production takes place in a laboratory rather than a mine, using one of two methods: High Pressure High Temperature (HPHT), which replicates the conditions under which natural diamonds form, or Chemical Vapour Deposition (CVD), which grows diamond crystal from a carbon-rich gas. Both methods produce stones that are chemically and optically identical to natural diamonds.
The lab-grown pipeline is compressed. A single facility can grow, cut, and sometimes even sell directly to the consumer. There are no sightholders, no tenders, no secondary rough markets. Supply is theoretically unlimited and can be scaled to meet demand — which is why lab-grown diamond prices have fallen significantly since the technology became commercially viable.
Sorting and grading follow the same standards as natural diamonds. The GIA and other laboratories grade lab-grown stones using the same criteria, though reports clearly identify the stone's origin. Trading happens through many of the same channels, though dedicated lab-grown platforms and direct-to-consumer brands are increasingly common.
The key difference is not quality — it is rarity. A natural diamond's journey through the pipeline, from geological formation to your hand, is unrepeatable. A lab-grown diamond's journey is reproducible by design.
Summary
- The pipeline has five stages: mining, sorting, cutting, trading, and retail. Each adds value, cost, and human skill.
- Most of the world's diamonds are cut in Surat, but the highest-value stones pass through Antwerp, Tel Aviv, and New York.
- Rough diamond pricing is controlled through mechanisms like De Beers' sightholder system and competitive tenders.
- The polished market is benchmarked against the Rapaport Price List, with individual stones trading at premiums or discounts.
- Lab-grown diamonds follow a compressed pipeline with lower barriers to entry and fundamentally different economics.
- Provenance and traceability are increasingly important to consumers — understanding the pipeline helps you ask the right questions about where your diamond came from and who handled it along the way.
Related reading: Diamond Cutting & Manufacturing Basics | Why Antwerp Matters | Pricing Basics | A Short History of Diamonds in Jewellery