It was the morning of 24 September 2023 when a returning space capsule appeared in the skies over the US Department of Defense’s Utah Test and Training Range. Floating down to Earth under a parachute was a single canister containing 121g (4.3oz) of material from the surface of an asteroid called Bennu.
Collected by NASA’s OSIRIS-REx mission, it’s a taste of things to come. For decades now, since the Apollo astronauts returned Moon rocks for analysis, astronomers and planetary scientists have been keen to get their hands on samples from other celestial bodies. But only in the last few years has technology been able to allow them to do it.
A little over a year on from OSIRIS-REx touching down and we now know that the Bennu samples contain both carbon-rich compounds and water-rich minerals. In January 2025, scientists confirmed that the asteroid even has a richer variety of organic matter than we have on Earth and contains all of the ingredients that make up DNA.
This indicates that asteroids like Bennu, which are remnants of a much earlier time in the Solar System, could have delivered the essential chemical building blocks of life to Earth in its earliest days.
Such insights come at a cost, however. The OSIRIS-REx samples are now one of the most expensive substances on Earth, clocking up an extraordinary price tag of $9.6 million (approx. £7.9 million) per gram.
But this sample isn’t the only material garnering a huge price tag. Many other incredibly rare and expensive materials far exceed what the asteroid sample cost to procure.
These are the world’s seven most expensive materials – though it’s worth noting that, since many of the substances here aren’t traded as common commodities, price estimates can vary widely. So, take all of the following with a pinch of salt (around $0.0011 per gram).
7. Helium-3 - $96,000 (approx. £79,000) per gram
Future valuation: $3 million (approx. £2.5 million) per gram
Helium-3 is a light isotope of helium, meaning it’s missing the second neutron found in common varieties of the gas. It’s scarce in Earth’s atmosphere and most of it comes from the radioactive decay of the hydrogen isotope tritium, which is also a rare substance.
Tritium, valued at around $29,000 (approx. £24,000) per gram, is used in nuclear weapons and some types of nuclear reactors. With a half-life of just over 12 years, it’s constantly producing helium-3, yet the world’s annual production is only between 10–20kg (22–44lbs).
Most of this production is managed in special governmental facilities such as those controlled by the US Department of Energy, which then make it available for commercial and research purposes.
The isotope is highly sought after for nuclear inspection tools due to its ability to detect stray neutrons. It can also be used in the advanced cryogenic (cooling) systems needed for quantum computers and superconducting devices.
In the future, it could serve as a clean fuel for nuclear fusion reactors, but here the demand would clearly outstrip the current supply. However, the lunar surface is thought to have soaked up helium-3 atoms during the entirety of its four-billion-year existence and so the isotope could – in theory – be mined there and shipped back to Earth.
The cost of such an extraterrestrial operation, combined with the isotope’s value in providing clean energy to the world, could drive the price to $3 million (approx. £2.5 million) per gram.
6. Emeralds, rubies and sapphires - $483,000 (approx. £395,000) per gram
As anyone who likes to wear sparkling things will tell you, these gemstones are highly prized for use in jewellery. Their value derives from their natural rarity and their beauty after the raw stone has been worked into a dazzling jewel by a skilled craftsperson.
Emeralds are rarer than ordinary diamonds, gaining their unique colour from the elements chromium and vanadium inside them. Rubies also get their deep-red colour from chromium. Sapphires are famously blue, but can actually occur in other colours depending on what metal is present.
Four factors influence the price of a gemstone. Known as the four Cs, they are: colour, with vivid hues being the rarest; clarity, with fewer imperfections hiking prices; cut, revealing the craftsperson’s ability; and carats, with larger stones being much rarer and therefore more valuable. (Also a measure of the purity of gold, carats are a unit of weight for precious stones. 1 carat is 0.2g, or 0.007oz).
Another significant factor is the gemstone’s cultural, historic and symbolic meaning. Coveted by royalty as emblems of status and transformed into talismans of love and affection by the jewellery trade, these rare natural treasures are also prized by investors.
In recent years, the newly discovered mineral painite has established a place for itself in the jewellery trade. Found only in Myanmar, it’s a rare borate mineral whose chromium and vanadium inclusions give it a red colour. Not (yet) as expensive as emeralds, rubies and sapphires, its value lies around $289,000 (approx. £237,000) per gram.
5. Red diamonds - $4.7 million (approx. £3.9 million) per gram
The value of red diamonds comes from their extreme rarity, with fewer than 30 known to exist across the world. They’re found in only a few diamond mines in Australia, Brazil and South Africa, and most of them originate from one place in particular: the Argyle Diamond Mine in Western Australia.
Mining operations were in full swing at Argyle by the mid-1980s after a single ore pipe was discovered in 1979. But, in 2020, Argyle was closed by its owners because – after 865 million carats of rough diamonds were hewed from the rocks – the pipe was reaching exhaustion. Red diamonds only made up a vanishing fraction of this total.
Coloured diamonds, more generally, aren’t uncommon, including orange, blue and yellow diamonds. Often these occur because of impurities in the form of other elements – such as nitrogen in the case of the yellow diamonds and boron in the case of the blue ones.
Yet the mystery behind the colour of red diamonds remains unsolved, as there aren’t any impurities in them. Instead, scientists think the diamond’s crystalline lattice structure may somehow be contorted during its formation. If this is the case, it’s the way light interacts with the diamond that creates the colour.
Most red diamonds are small, weighing in at less than a carat. The largest example wasn’t found in Australia, but in Brazil – weighing 13.9 carats (2.8g, or 0.1oz) as a rough stone, and 5.11 carats (1g, or 0.04oz) when cut into a jewel.
It’s now known as the Moussaieff Red Diamond, named after the jeweller who bought it in around 2001 for an undisclosed sum.
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4. Samples of asteroid Bennu - $9.6 million (approx. £7.9 million) per gram
This is where the OSIRIS-REx samples come in. Standing for Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer, the OSIRIS-REx mission targeted asteroid Bennu because it was thought to be a special type of asteroid: one that’s rich in organic molecules.
As such, it could contain unprecedented insights into the way life started on our planet.
The samples will also provide scientific insights into how we might be able to deflect an asteroid spotted on a collision course with Earth, as well as clues about the future of advanced space exploration – like which materials we could mine from asteroids.
The cost of the sample is calculated surprisingly simply: by dividing the cost of the mission by the quantity of material it returned. In the case of OSIRIS-REx, the design, launch and operation came in at around $1.1 billion (approx. £950 million).
If everything had gone as expected, the cost per gram would have been roughly double because the mission was only expected to capture around 60g. But at a total of 121g (4.3oz) of asteroid, the sample turned out to be less scarce – and therefore less valuable.
A previous asteroid sample-return mission, Japan’s Hyabusa-2, delivered samples of asteroid Ryugu in 2020. Based on a similar method of calculation, these samples cost around $10.7 million (approx. £8.8 million) per gram. Although it only returned a scarce 5g (0.18oz), the mission was cheaper than OSIRIS-REx – making Ryugu’s cosmic contents less desirable.
3. Californium-252 - $25.6 million (approx. £21 million) per gram
Californium-252 (Cf-252) is a radioactive isotope that’s not found in nature and can only be made in nuclear reactors or particle accelerators. As suggested by its name, it was first made at the University of California’s radiation laboratory, in 1950.
Californium-252’s value comes from the fact that it’s a colossal source of neutrons. A single microgram of the isotope can produce around 139 million neutrons per minute. This makes it highly lethal, but crucial to certain applications – one being in nuclear reactors, where the isotope is used to jump-start the chain reactions that produce energy.
Neutrons can also be used to look inside solid structures, making Cf-252 highly sought-after for industrial imaging devices. Neutron radiography, as this technique is known, can help to detect internal corrosion, cracking or bad welds in many otherwise impenetrable machine components.
Another of its critical uses is in medicine, specifically as part of cancer treatments. The fact that the neutrons from Cf-252 are lethal to living cells means that they can be highly effective in tightly targeted radiation therapies against cancer cells.
That’s why, despite its great cost, Cf-252 is available commercially. In the US, it’s produced by the Oak Ridge National Laboratory, in Tennessee. In Russia, it’s synthesised at the Research Institute of Atomic Reactors, in Dimitrovgrad. Both produce less than a gram per year.
Contributing to its huge cost is the fact that even these tiny quantities need large, well-shielded containers to transport the deadly substance safely.
2. Nitrogen atom-based endohedral fullerenes - $134 million (approx. £110 million) per gram
Metamaterials are engineered substances with properties that are either rare or not found in nature at all. One example is carbon nanotubes – tiny cylindrical structures that can be just a few nanometres (a billionth of a metre) wide.
Despite their complexity, however, they’re now widely used in electronics and for creating strong, lightweight materials, especially in aerospace engineering. Relatively speaking, they’re dirt cheap, at around $482 (approx. £395) per gram, but at the cutting edge of the discipline things are very different.
Scientists at Designer Carbon Materials, a company with ties to the University of Oxford, have created a new substance called nitrogen atom-based endohedral fullerene that recently sold for the equivalent of $134 million (approx. £110 million) per gram.
A fullerene is a mostly manufactured molecule that contains 60 carbon atoms arranged in a closed structure that resembles a football with pentagonal and hexagonal panels. This similarity led to this fullerene being nicknamed ‘buckyballs’ after its first generation in a lab in the 1980s.
In effect, the carbon atoms form a cage-like structure that Designer Carbon Materials cleverly thought to trap a nitrogen atom inside.
Nitrogen is special because the magnetic field generated by the atom’s nucleus interacts with the one generated by its electrons. This causes the electrons to transition between energy levels, producing the equivalent of a ‘tick’ in a clock.
So, in principle, nitrogen atom-based endohedral fullerene could be used to create minuscule atomic clocks – which, among other things, are the very basis of satellite navigation.
At present, the atomic clocks in navigation satellites are about the size of shoeboxes. But using this particular fullerene could make them fit inside a mobile phone.
1. Antimatter - $59.8 trillion (approx. £49 trillion) per gram
Well known to science-fiction fans as the power source that keeps Star Trek’s starship USS Enterprise hurtling along at warp speed, antimatter was theorised to exist by English mathematician Paul Dirac in 1928 and discovered in reality by Carl Anderson in 1932.
When antimatter and matter come into contact, they annihilate each other and convert into pure energy. In fact, this process is the most efficient known way to liberate energy in the Universe.
To harness antimatter as a fuel source would revolutionise everything. It would solve our power needs on Earth and provide so much energy that it could make interstellar travel practical by propelling our spacecraft to unprecedented speed (even if warp drive remains a figment of the imagination).
The reason for its astronomical cost stems from how it’s made. Currently, antimatter has to be manufactured artificially in particle accelerators such as CERN’s Large Hadron Collider (LHC), located underground along the French-Swiss border.
The antimatter produced by the LHC is a by-product of its experiments exploring the nature of matter. In other words: scientists aren’t farming it, as such. To harvest it would involve the use of complex magnetic ‘bottles’, also known as Penning traps, which prevent the antimatter from touching the container walls and causing an explosion.
Even if that were possible, the cost of producing antimatter is truly astronomical. The LHC cost around $5.49 billion (approx. £4.5 billion) just to build, and comes to around $977,000 (approx. £800,000) per year to operate. Each year, it produces less than a nanogram of antimatter.
So, unless we have a miraculous technological breakthrough, antimatter will remain a tantalising yet elusive substance.
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