Natural Diamond Value Over Time: Geology, History, Argyle and What It Means for You

What does natural diamond value over time actually mean?

When people ask whether diamonds hold their value, they are usually mixing up several different numbers. A diamond does not have one value. It has a price in a shop, a cost to replace it if it is lost, a price between traders and a price a buyer will pay you if you sell it. Those numbers can be thousands of dollars apart for the same stone, and they move in different ways over the years.

• Retail price: what you pay a jeweller today, including cutting, grading, setting, staff and the shop's margin.
• Replacement value: what it would cost to buy an equivalent diamond new, usually the figure on an insurance valuation.
• Wholesale price: what jewellers and dealers pay each other for loose stones, often tracked by trade price lists quoted in US dollars.
• Resale value: what a dealer, pawnbroker, auction house or private buyer will actually pay you for a second-hand diamond.

The physical diamond barely changes over a lifetime. What changes is the market around it. If you are new to the topic, our complete guide to natural diamonds covers the basics, and how carat, colour, clarity and cut set a diamond's price explains why two stones of the same weight can differ so much. Any unfamiliar term below is defined in our A–Z jewellery glossary.

How old are natural diamonds, and how do they form?

Most natural diamonds crystallised between about 1 and 3.5 billion years ago, roughly 140–200 kilometres below the surface, in the Earth's mantle (the thick layer beneath the crust). There, temperatures of about 900–1,300 °C and enormous pressure squeeze carbon atoms into the tight cubic structure that makes diamond the hardest natural material, 10 on the Mohs scale, with a refractive index of about 2.42.

Diamonds reach the surface inside rare, deep volcanic eruptions. The rock that carries them is usually kimberlite, named after Kimberley in South Africa, or, less often, lamproite, the rock at Australia's Argyle mine. These eruptions are ancient; no diamond-bearing eruption has happened in recorded history. Our page on how natural diamonds form deep in the mantle goes through each stage.

That journey leaves fingerprints. Natural diamonds often show growth patterns, mineral inclusions and clustered nitrogen that laboratory-grown stones usually do not. Sometimes a cutter leaves a small patch of the original crystal skin on the finished stone to save weight. You can read about these in naturals left on a diamond's girdle and indented naturals that dip below the surface. They are evidence of a natural origin, but on their own they do not make a diamond worth more.

How did natural diamonds become so valuable?

For most of history, diamonds were extremely scarce. India was the main source for well over a thousand years, then Brazil from the 1720s. The picture changed in 1867, when a diamond was found near the Orange River in South Africa, followed by the rush to Kimberley. Suddenly there were far more diamonds than the old market could absorb, and prices were at risk of collapsing.

For most of the 20th century, De Beers and its selling organisation handled a large share of the world's rough (uncut) diamonds, often quoted at around 80–90%. By holding back stock when demand was weak, it kept prices steady. That is why many people grew up believing diamond prices only go up. Once that system loosened around 2000, prices began to rise and fall more like other goods.

What role did Argyle play in Australia's diamond story?

The Argyle mine in the East Kimberley region of Western Australia was found in 1979 and began producing in the early 1980s, first from alluvial deposits and then from the open pit, later moving underground. Over its life it produced more than 865 million carats, at times more diamonds by volume than any other mine in the world.

Most of Argyle's output was small and brown, much of it suited to industrial use or lower-priced jewellery. Rather than treat brown as a fault, Argyle marketed it with a champagne and cognac colour scale, graded C1 (lightest) to C7 (deepest). That changed how many people saw brown diamonds.

Argyle is best known for its pink diamonds. They were a tiny fraction of production, yet the mine supplied the large majority of the world's pinks, often quoted at around 90%. The finest were sold each year through an invitation-only tender. Since the mine closed in November 2020, results for top Argyle pinks have been widely reported as strong, but these are rare collector stones sold in very small numbers. They tell you nothing about how an ordinary colourless diamond will behave.

Australia had other diamond mines too: Ellendale in the West Kimberley produced fancy yellow diamonds until about 2015, and Merlin in the Northern Territory operated briefly around 2000. Today Australia is not a significant producer, so most natural diamonds sold here are mined in places such as Botswana, Russia, Canada and South Africa.

Has natural diamond value over time gone up or down?

Both. Over several decades, retail prices for natural diamonds have generally risen in dollar terms, but not smoothly and not always faster than inflation. There have been clear falls along the way:

The 1980 episode is the clearest lesson. Top-colour, flawless one-carat stones were bid up to extraordinary levels and lost a large part of that value within a couple of years. Ordinary jewellery diamonds were far less affected, but people who bought diamonds purely to sell later lost money.

Two less obvious factors matter for Australians. First, diamonds are traded internationally in US dollars, so the Australian price moves with the exchange rate. A falling Australian dollar can lift local prices even when world prices are flat. Second, size changes everything. Larger natural diamonds are far rarer, so price per carat jumps at weights such as 0.50, 1.00, 1.50 and 2.00 carats, and very large, top-quality stones have historically been steadier than small ones.

For how the price climbs as stones get bigger, see why natural diamonds get rarer, and pricier, as they grow.

Do natural diamonds hold their value when you resell?

Usually not in the way people hope. A natural diamond keeps a real resale market, but the price a buyer offers is normally well below what you paid at retail. The gap covers the retailer's costs, the buyer's need to resell at a profit and the fact that second-hand stones compete with plenty of new ones. As a broad guide, offers for second-hand diamond jewellery often land somewhere around 20–50% of the original retail price, depending on the stone, the report and who is buying.

This is why an insurance valuation can say one figure while a dealer offers you much less. Neither is wrong; they answer different questions. Our guide to replacement value versus resale value explains how valuations are prepared and why you should update them every few years.

How have lab-grown diamonds changed natural diamond value?

Lab-grown diamonds are real diamond, with the same chemistry, hardness and sparkle as natural stones, grown in weeks in a laboratory instead of over billions of years underground. As production has grown, their retail prices have fallen sharply, and many buyers who once would have chosen a smaller natural diamond now choose a larger lab-grown one. That has put pressure on prices of smaller and mid-range natural diamonds.

The natural premium comes from rarity and origin, not from looks. You cannot tell the two apart by eye, and a basic tester cannot either; see whether a handheld diamond tester can spot lab-grown and the instruments laboratories use to confirm origin. For a full side-by-side, read lab-grown versus natural diamonds compared, and for the wider gem picture, the difference between natural, synthetic and simulant gems.

Why does a grading report matter for a natural diamond's long-term value?

If you ever sell, insure or pass on a natural diamond, the first thing anyone asks for is the grading report. A report from an independent laboratory such as GIA or IGI records the measurements, colour, clarity and cut, and states that the diamond is natural. Without one, a buyer has to pay for testing or will simply offer less.

The report also discloses treatments, which affect value a great deal. Some natural diamonds are put through high-pressure, high-temperature processing to improve their colour; this is covered in HPHT-treated natural diamonds. Others are laser-drilled or fracture-filled to hide inclusions. A treated natural diamond is still natural, but it is normally worth less than an untreated stone of the same grades.

Reports for natural and lab-grown stones look similar but say different things; how natural and lab-grown reports differ shows what to look for, and a line-by-line walk through an IGI natural report decodes each field. Keep the original report with the ring, and a copy somewhere separate.

What happens to a natural diamond over generations?

Physically, very little. A natural diamond does not fade, cloud or wear out. It can chip if a thin edge takes a hard knock, and it can look dull when skin oils and soap build up underneath, but a clean and a check of the claws usually brings it back. A chip can often be removed by re-polishing, at the cost of a small amount of weight.

That durability is where a natural diamond keeps its value for most families: not as a price on a screen, but as a stone that can be reset again and again. A diamond from a grandparent's ring can move into a new engagement ring, a pendant or a pair of earrings, keeping its history while the setting changes with the times.

How should you weigh value when buying a natural diamond? Step by step

If you are deciding between natural and lab-grown, or between gemstones, natural and lab-grown options for engagement rings sets out the trade-offs. Then work through these steps.

1. Decide why you want natural. Rarity, age and origin are good reasons. Expecting it to make money is not.
2. Get an independent report. Make sure it confirms natural origin and lists any treatment.
3. Compare prices across grades. Small drops in colour or clarity can save a lot without a visible difference.
4. Ask about resale and replacement. Understand both numbers before you commit.
5. Insure it at replacement value. Get a written valuation and update it every two to three years.
6. Keep the paperwork together. Report, valuation and receipt make any future sale, claim or remodel far easier.