Reviewed August 2026 against Sotheby’s auction records, Johnson Matthey PGM base prices and the USGS Mineral Commodity Summaries.

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Most Expensive Mineral: What Actually Holds the Record

By verified transaction price, the most expensive mineral in the world is gem-quality diamond, and the record has a receipt attached: the 11.15-carat Williamson Pink Star sold at Sotheby’s Hong Kong on 7 October 2022 for US$57,736,078 — US$5,178,124 per carat, which Sotheby’s confirmed as a world record price per carat for any diamond or gemstone. Measure by bulk weight instead and the answer flips entirely: rhodium, iridium and ruthenium are the priciest routinely mined materials, quoted in dollars per troy ounce rather than per carat. Nearly every “most expensive mineral” list online mixes those two units without saying so, and most add californium-252 — which is not a mineral at all.

This page does three things a summary cannot: it gives you the verified numbers with their dates and sources, it gives you a test for deciding which claim is actually true, and it gives you the exact pages where you can pull a fresher price than ours in about four minutes.

Table of Contents

The four-question test for any “most expensive mineral” claim

Ranked lists of expensive minerals disagree wildly because they answer different questions without admitting it. Run any claim through these four questions and the disagreement disappears. This test does not expire when the prices move.

1. Is it a mineral? A mineral is naturally occurring, inorganic, solid, with a defined chemical composition and an ordered crystal structure. Diamond, jadeite, painite and red beryl pass. Refined rhodium sponge is a manufactured product from a mineral; californium-252 is made in a reactor and fails outright.
2. Per what unit? Gemstones trade per carat (0.2 grams). Platinum-group metals trade per troy ounce (31.1035 grams) — 155.5 carats. A price quoted per carat is inflated 155-fold against one quoted per ounce before you compare anything.
3. Was it transacted, or estimated? An auction hammer price with a lot number is evidence. “Valued at $12.8 million” for a stone nobody has sold is not. Insist on a named sale, a named house and a date.
4. Is the material fungible? Rhodium is rhodium; any two ounces of 99.9% sponge substitute for each other, so one price governs the market. Every fancy red diamond is a unique object, so a per-carat record describes one stone, not a market you can buy into.

Apply the test and the honest answer becomes two answers rather than one, which is exactly why this question survives so much argument.

The contenders, side by side, with sources and dates

Every row below carries the unit it was quoted in, the source, and when that figure was set. Nothing here is normalised for you — normalising is the trick that produces misleading rankings, and the calculator further down lets you do it yourself with your own numbers.

Two things in that table are worth pausing on. First, the platinum and palladium figures come from the London Platinum and Palladium Market, which publishes reference prices for those two metals only. Rhodium, iridium, ruthenium and osmium have no exchange fixing at all — they trade over the counter against dealer assessments, which is a structural reason their prices swing harder than gold’s. Second, the californium row is deliberately empty of a number: the DOE’s National Isotope Development Center lists Cf-249 and Cf-252 in microgram quantities on a request-a-quote basis and does not publish a price. The “$27 million per gram” figure circulating online is not sourced to that catalogue.

The gemstone case: fancy red and pink diamonds

If the question is “what is the most expensive mineral in the world” and you accept a per-carat basis, the contest is between coloured diamonds and it is not close. The Gemmological Association of Great Britain puts the population of unmodified red diamonds at fewer than 30 known stones, noting that depending on grading criteria the figure could reach the low hundreds. Fancy-coloured diamonds of any hue account for roughly one in 10,000 diamonds, and blue stones make up about 0.3% of those.

The largest known red diamond is the Moussaieff Red at 5.11 carats, from rough found in Brazil in the 1990s. The Kazanjian Red is 5.05 carats and the DeYoung Red 5.03 carats. The benchmark transaction remains the Hancock Red, 0.95 carats, sold in 1987 for $880,000 — $926,316 per carat in 1987 dollars, a number that startled the trade at the time. All of these figures come from Gem-A’s analysis published 25 April 2024, which also explains the cause: red colour comes from plastic deformation of the crystal lattice during continental collision, concentrating along glide planes rather than from a trace element.

The supply side changed permanently in November 2020. Rio Tinto confirms it closed the Argyle mine in Western Australia that month after 37 years and more than 865 million carats of rough production, and that pink stones were only “a tiny proportion” of that output. Rio Tinto’s only remaining diamond operation is Diavik in Canada’s Northwest Territories, about 200 km south of the Arctic Circle, which yields large white gem-quality stones and under 1% yellows. There is no replacement source of pink and red rough at Argyle’s scale, and the per-carat record moved almost two years after the closure.

The metals case: rhodium, iridium, ruthenium, osmium

Ask an industrial buyer what the most expensive mineral is and you will get a platinum-group metal, because that is what actually shows up on a purchase order. Johnson Matthey publishes Base Prices in US dollars per troy ounce for six metals — platinum, palladium, rhodium, iridium, ruthenium and osmium — and those quotes are the reference the trade uses. The prices apply to sponge at minimum purities of 99.95% for platinum and palladium and 99.9% for rhodium, iridium and ruthenium. That purity specification matters: an off-spec lot does not fetch the quoted number.

For a producer’s-eye view of what the complex actually earned, Valterra Platinum (formerly Anglo American Platinum) reported a realised PGM basket price of US$1,852 per ounce for the 2025 financial year, 26% above 2024, in its Integrated Report 2025. A basket price blends every metal a mine ships, so it is not a rhodium price — it is the useful figure for judging whether the sector as a whole is being paid more or less.

On direction of travel, the clearest published guidance comes from Johnson Matthey’s PGM Market Report. In its 2026 edition the company states that every PGM was in deficit during 2025, that platinum reached an all-time high in January 2026, and forecasts for 2026 that platinum demand falls 8%, palladium 9%, rhodium 6% and ruthenium 6%, while iridium demand could edge higher. Johnson Matthey expects further shortfalls in platinum, ruthenium and iridium during 2026 with small surpluses possible in palladium and rhodium. Market Research Director Rupen Raithatha is quoted saying PGM consumption in industrial applications is forecast to be robust, despite ongoing geopolitical uncertainty. Those are company forecasts for calendar 2026, not outcomes — treat them as such.

Calculator: carats vs troy ounces on one scale

Put a gemstone price and a metal price into the same unit and the comparison finally means something.

"Most expensive item on earth" — the adjacent question

Search traffic for the most expensive mineral overlaps heavily with the most expensive item on earth, and they have different answers. No mineral specimen comes near a large engineered object. The US Government Accountability Office, in testimony GAO-08-581T dated 24 April 2008, put NASA's expected final construction cost for the International Space Station at $31 billion with a further $11 billion in sustainment through the then-planned retirement in fiscal year 2016 — a combined $42 billion US investment, and that excludes international partner contributions and later extensions. Higher totals you will see quoted include shuttle launch costs and post-2016 operations, so always check what a headline figure contains before comparing it to anything.

Why californium-252 keeps appearing, and why it does not count

Californium-252 dominates "most expensive substance" lists because the per-gram figure is spectacular. It fails question one of the test outright. Cf-252 is produced by irradiating curium targets in high-flux reactors, it has a half-life of about 2.6 years, and it exists in milligram quantities worldwide. It is not naturally occurring, not crystalline in any mineable form, and there is no deposit of it anywhere on Earth. Calling it the most expensive mineral is a category error, not a close call.

The DOE's National Isotope Development Center catalogue is the authoritative US source for what Cf-252 actually costs a buyer, and it is quote-based rather than list-priced. If you need a defensible figure for a procurement document, request a quote through that catalogue rather than repeating a number from an aggregator. The same discipline applies to any exotic-material price you are asked to justify.

How to check every one of these prices yourself

Prices on this page carry their date because they will move. Here is the refresh path for each, so you can always get a fresher number than ours.

1. Rhodium, iridium, ruthenium, osmium, platinum, palladium. Johnson Matthey's Base Price page quotes all six in US$ per troy ounce and updates on trading days. Read the purity footnote before you use a number in a contract.
2. Platinum and palladium reference prices. The LPPM publishes those two only. If a source claims an exchange fixing for rhodium or iridium, it is wrong.
3. Supply and demand by metal. Johnson Matthey's PGM market data downloads run from 1975 onward by region for platinum, palladium, rhodium, ruthenium and iridium, with the file set refreshed periodically — the release available when we checked was dated May 2026.
4. US production, imports, reserves and import reliance. The USGS Mineral Commodity Summaries, published 6 February 2026 for the 2026 edition, is the earliest comprehensive source of prior-year world production data and is reissued annually in late January or February.
5. Gemstone records. Only accept a lot-level figure from the auction house's own press release, with carat weight, hammer total and the per-carat arithmetic shown. Sotheby's and Christie's both publish these.
6. Producer economics. Listed miners disclose realised prices in annual and interim results. Valterra Platinum, Sibanye-Stillwater and Impala Platinum all publish them, and a realised price tells you what was actually banked rather than what was quoted.

That six-step routine is the durable part of this page. Whatever the numbers do, the sources stay the same.

Where satellite mineral detection fits

Nothing on this page changes the physics of exploration: you still need ground truth before you can call anything a deposit. What earth observation changes is the cost of the first filter. Farmonaut analyses multispectral and hyperspectral reflectance to map spectral signatures across large, remote areas, so that field budgets go to a shortlist rather than a region. For the metals discussed above — where output is measured in tonnes per year and a single new source moves the market — that filtering step is where most of the leverage sits.

• Screen before you fly. Assess wide areas from orbit and rank targets before committing to airborne or ground crews.
• No ground disturbance at the screening stage, which matters for permitting timelines and community consent.
• Georeferenced outputs delivered as PDF and GIS layers so they drop straight into an existing exploration workflow.
• Jump to the calculator

Deliverables include a Premium mineral intelligence report for early-stage assessment, and TargetMax™ Drilling Intelligence with 3D subsurface modelling for teams moving from detection towards a drill programme. Procurement teams pairing exploration intelligence with structured risk management for mining get a fuller picture than either gives alone.

Frequently asked questions

What is the most expensive mineral in the world?

On a per-carat basis, gem-quality diamond, and the highest verified figure is US$5,178,124 per carat for the 11.15-carat Williamson Pink Star at Sotheby's Hong Kong on 7 October 2022. On a bulk-weight basis, platinum-group metals lead, with rhodium historically the dearest of the six quoted by Johnson Matthey. Both statements are true; they answer different questions.

Is rhodium more expensive than diamond?

Per gram, no — and it is not close. Convert the Williamson Pink Star record and you get roughly $25.9 million per gram of stone. Put any plausible rhodium quote into the calculator above and the gap runs to five or six orders of magnitude. Per tonne of tradeable market, rhodium is far larger, because there is no market in fancy red diamonds at scale.

Which mineral is rarest rather than most expensive?

Rarity and price are not the same variable. Gem-A counts fewer than 30 known unmodified red diamonds, which makes red diamond among the scarcest gem materials in existence — yet the highest per-carat auction figure belongs to a pink stone, because bidders competed for it in an open room. Several minerals known from only a handful of grains worldwide have no price at all, because none has ever been offered for sale.

Why did coloured diamond prices rise after 2020?

The Argyle mine in Western Australia closed in November 2020 after 37 years and more than 865 million carats of rough, per Rio Tinto, and it was the dominant source of pink rough. Rio Tinto's remaining diamond mine, Diavik in Canada, produces predominantly large white gem-quality stones. The Williamson Pink Star record followed in October 2022. Supply withdrawal is a plausible contributing factor; a single auction result is not proof of a market-wide shift, so watch subsequent tender and auction results rather than one lot.

What would change the answer on this page?

Three things. A new per-carat auction record above $5,178,124 would move the gemstone answer. A sustained rhodium or iridium move would reorder the metals table — Johnson Matthey forecasts small surpluses in palladium and rhodium during 2026 alongside continued shortfalls in platinum, ruthenium and iridium, which points to divergence rather than a uniform trend. And a discovery of a pink or red diamond source at Argyle's scale would reset the gem side entirely; none has been announced.

Where do I get an official US figure for production and reserves?

The USGS Mineral Commodity Summaries, published annually by the National Minerals Information Center; the 2026 edition was released on 6 February 2026 and carries prior-year world production, reserves and US net import reliance for more than 90 commodities. It is the standard citation for any US procurement or policy document.

The bottom line

"Most expensive mineral" is not one question. Ask it per carat and the answer is a coloured diamond with a documented $5,178,124-per-carat auction record. Ask it per ounce and the answer is a platinum-group metal you can price on a Johnson Matthey page in under a minute. Ask it about materials generally and californium-252 enters, and immediately fails the definition of a mineral. Ask about the most expensive item on Earth and you leave minerals altogether for a $42 billion orbital laboratory.

Keep the four-question test and the six-source refresh routine, and you will be able to answer this correctly whatever the numbers do. For teams whose interest in expensive minerals is operational rather than academic, the practical starting point is narrowing where to look: satellite-based mineral intelligence is built to do exactly that before the drill budget is committed.