Humanity's tech tree has finally unlocked alchemy.

Throughout the long history of humanity, the myth of "turning stone into gold" has always been one of the most fascinating ultimate fantasies.

From the smoke-shrouded underground chambers of medieval Europe to the alchemy furnaces sought across the realm by ancient Eastern emperors, countless alchemists and scientific giants — including Isaac Newton, the father of modern physics — were obsessed with alchemy, attempting to extract shining gold from cheap lead or mercury. However, over thousands of years, none of these attempts ended in success.

With the establishment of the modern chemistry system, humanity finally realized that chemical reactions can only operate on the electron clouds outside atoms, and cannot change the number of protons inside the atomic nucleus. The "gap of one single proton" between element 79 gold (Au) and element 80 mercury (Hg) is an insurmountable natural moat at the chemical level.

For this very reason, in the common sense of modern finance and physics, gold has always been regarded as the ultimate scarce resource that is constant in nature and cannot be artificially counterfeited — every gram of gold on Earth comes from cosmic cataclysms such as supernova explosions or neutron star collisions billions of years ago. The reason why gold has become the cornerstone of hard currency and value storage spanning thousands of years is precisely built on this iron law of "physically impossible to increase supply".

However, this underlying logic that has lasted for thousands of years is facing unprecedented impact in a laboratory in downtown San Francisco.

On October 22, Marathon Fusion, a Silicon Valley nuclear fusion startup, made a high-profile announcement that it has demonstrated a high-rate modern version of "alchemy" — using the high-energy neutron flow generated by nuclear fusion, it successfully converted mercury into real, stable gold, and the conversion rate has broken the record set by CERN in 2025 by a full 10 times.

Where did Marathon Fusion come from? Is the so-called "turning mercury into gold" really scientifically grounded? When "alchemy" becomes reality, will the narrative of gold's scarcity be rewritten? All the answers start from the rebellious technical route of this Silicon Valley hard-tech startup.

Marathon Fusion's Ambition: From "Turning Mercury Into Gold" To A Commercial Empire Of Nuclear Transmutation

Marathon Fusion was founded in San Francisco in 2023. Its two co-founders are Kyle Schiller (CEO), who previously served as a science policy researcher at Schmidt Futures, the foundation under former Google CEO Eric Schmidt, and Adam Rutkowski (CTO), a former SpaceX propulsion engineer with a background in Princeton plasma physics.

At the initial stage of its establishment, Marathon Fusion received approximately $4 million in grants from the U.S. government, and also completed a $5.9 million seed round of financing. The company originally focused on solving the most difficult underlying problem of "tritium fuel cycle and separation" for nuclear fusion reactors. However, during its R&D in 2025, the team accidentally calculated a disruptive economic account — instead of waiting decades to make money selling electricity from nuclear fusion, it is better to use the high-energy neutron flow generated by fusion to start "Nuclear Transmutation" (which refers to directly changing the structure of the atomic nucleus through nuclear reactions to convert one element into another), and achieve commercial closed-loop in advance by co-producing gold and sky-high medical isotopes. Today, this hardware engineering team of only 28 people, with less than one fifth of them holding doctorates, is trying to build a full-stack nuclear fusion device from scratch.

A careful breakdown of the technical route and experimental video disclosed by Marathon Fusion shows that its promoted "turning mercury into gold" is by no means a simple eye-catching scientific magic trick, but a key link in its huge commercial blueprint of "Scalable Transmutation".

Core Architecture: Reviving The Classic Solution From The 1980s

Different from the vast majority of nuclear fusion companies that pursue large-scale power generation, Marathon Fusion has taken an extremely pragmatic engineering shortcut for its first-generation commercial reactor — Beam-Driven Fusion.

In the officially released technical video, the working principle of its first-generation reactor is very clear. First, melt and evaporate metallic lithium to attach it to a solid copper plate, then let this layer of lithium adsorb saturated hydrogen isotope (tritium) to form a solid target; then, ionize deuterium gas and accelerate it through a high-voltage electric field, and use a high-energy deuterium ion beam to directly bombard the target, thus triggering deuterium-tritium (D-T) nuclear fusion.

This architecture is not fabricated out of thin air. As early as the 1980s, Lawrence Livermore National Laboratory (LLNL) in the United States used a similar rotating tritium target neutron source (RTNS-II) to operate stably for more than 25,000 hours at high fusion power density.

Marathon Fusion combines modern molten lithium processing, radio frequency ion generation and plasma centrifuge technology — just last week, it broke the plasma centrifuge isotope enrichment record that the Soviet Union had kept for 40 years — to re-commercialize this classic architecture. Marathon Fusion's goal is to continuously bombard one trillion high-energy neutrons per second on a target with a diameter of only 1 centimeter, and achieve "doubling the fusion power density every month" within the next year, and it is expected to deliver the first generation of commercial reactors to the first batch of partners in 2027.

How is "turning mercury into gold" achieved?

Since gold cannot be produced by chemical methods, how can nuclear physics do it? The answer lies in the 14.1 MeV (mega-electron volt) high-energy fusion neutrons.

Every deuterium-tritium fusion reaction will eject a neutron with an energy as high as 14.1 MeV at an extremely high speed. When this "super bullet" bombards the stable isotope mercury-198 that exists in nature, a (n, 2n) nuclear reaction will occur — that is, one neutron crashes in, knocks out another neutron in the original atomic nucleus, and a total of two neutrons fly out.

At this time, mercury-198 that has lost a neutron becomes an unstable radioactive isotope mercury-197. After several days of half-life decay (electron capture), one proton in the mercury-197 nucleus is converted into a neutron, and element 80 mercury naturally decays into element 79 — gold-197, which is also the only stable gold isotope in nature.

The reason why this process must rely on nuclear fusion is that the energy threshold to trigger this reaction is above about 6 MeV. The neutrons generated by traditional nuclear fission power plants are too low in energy to move the mercury atomic nucleus at all; and each ignition of the fusion reactor can accurately produce such high-energy neutrons. More importantly, in Marathon Fusion's reactor design, the two neutrons knocked out from mercury-198 will not be wasted. They will continue to bombard lithium-6 in the cladding, split to produce the reactor's required fuel tritium and helium-4, thus achieving the three goals of "power generation + fuel breeding + gold making" in one move in the future.

The Real Money Printer: There Are Things A Billion Times More Expensive Than Gold

Although "making gold" sounds attractive enough, at the current stage, Marathon Fusion's real commercial core is actually rare medical isotopes.

The so-called medical isotopes can be called the "biological nuclear missile" in the field of modern precision medicine — after combining them with specific targeting molecules and injecting them into the patient's body, they can accurately lock the tumor, and use the rays released by their own decay to eliminate cancer cells from a fixed point inside, without harming the surrounding healthy tissues. However, most of these isotopes have extremely short half-lives (they cannot be stored for a long time, and must be produced and used immediately), and the remaining few old fission research reactors in the world have long been on the verge of capacity limits. The extreme imbalance between supply and demand makes them often priced by "microgram" or even "millicurie" in the pharmaceutical market. Converted to gram weight, their unit price is as high as tens of millions to tens of billions of US dollars, making them one of the most valuable substances per unit value on Earth.

In recent years, Targeted Radiotherapy has seen exponential explosive growth in the field of cancer treatment. Novartis' prostate cancer nuclear drug Pluvicto has a unit price as high as $42,500, with sales of $1.9 billion last year, and even had to suspend accepting new patients for a time due to the interruption of upstream isotope supply. Pharmaceutical giants such as Eli Lilly and Bristol-Myers Squibb have invested billions of dollars in crazy acquisitions of nuclear drug assets.

If the mercury target in the Marathon Fusion reactor is replaced with other metals, it will generate different medical isotopes through transmutation, turning into a real money printer:

In the latest experiment, Marathon Fusion has successfully used fusion neutrons to bombard zinc (Zn) to transmute radioactive copper isotopes used for cancer diagnosis and cutting-edge therapies;

The official demo video also shows the path of bombarding europium-151 to finally generate terbium-149, which is urgently needed for anti-cancer treatments;

If the target material is replaced with radium-226, the same (n, 2n) reaction can generate the extremely scarce actinium-225 — the core raw material of Novartis' next-generation anti-cancer wonder drug, whose global annual output is only enough for several thousand patients.

As Marathon Fusion said in its promotional video — in the 20th century, humanity invented synthetic ammonia fertilizers, silicon semiconductors and aspirin that feed half of the population by "designing molecules" (synthetic chemistry); and now, they are opening an industrial revolution of "large-scale nuclear transmutation" by directly manipulating atomic nuclei.

Market Discussion: Neutrons Can Also Be Priced Explicitly, Gold Faces "Quantum Crisis"

Marathon Fusion's major official announcement quickly triggered cross-border discussions in the Silicon Valley tech circle, the nuclear energy industry, as well as Wall Street and the crypto finance circle. The focus of everyone's discussion is mainly on the following dimensions: Is nuclear transmutation gold making really profitable? How is this account calculated? What impact will it have on the pricing of gold and macro assets?

Calculating an economic account: Why shouldn't nuclear fusion companies only focus on "selling electricity"?

Aakash Gupta, a Silicon Valley AI research guru, made a wonderful financial breakdown of Marathon Fusion's paper data, directly revealing the secret of this company subverting the logic of the nuclear fusion industry — putting an explicit dollar price on every fusion neutron.

If we mark a dollar price for each Single Fusion Neutron emitted by the reactor according to the value it generates:

Used for power generation, one neutron is worth only about 3 × 10⁻²⁰ US dollars;

Used for gold making, one neutron is worth about 2.6 × 10⁻²⁰ US dollars (basically the same as power generation);

Used to produce molybdenum-99, which accounts for 80% of the share in nuclear medical scans, the value of one neutron jumps to 2.6 × 10⁻¹⁷ US dollars (nearly a thousand times that of power generation);

Used to produce actinium-225, the raw material of the anti-cancer wonder drug, converted into grams at the unit price of 1200 to 2500 US dollars per millicurie, its unit price is as high as tens of billions of US dollars per gram. This means that every neutron hitting the target is worth about 10⁻¹⁰ US dollars — a full 3 billion times the value of using it for power generation!

This account completely reconstructs the commercialization threshold of nuclear fusion. Aakash pointed out that traditional nuclear fusion companies are all striving for grid-connected power generation, but if selling electricity wants to break even, the ratio of plasma output energy to input heating energy must reach 10 to 22 times, while the best result of the world's top tokamak device (JET in the UK) is only about 0.33 times. If we follow Marathon Fusion's method, adding "gold making" as a by-product in the power generation cladding to subsidize costs, the break-even point is directly reduced to 3 times; if it is specially used to produce the medical isotope molybdenum-99, the break-even point plummets to 0.001 times!

In other words, even if the output energy of a fusion machine is only one thousandth of the input energy (which means it loses terribly in the sense of power generation), as long as its neutrons hit the right metal target, it can make money immediately now. A small machine with a power of only 3 megawatts (MW) is enough to cover all global supply of molybdenum-99.

And gold, as a huge market of about 700 billion US dollars a year, is enough to absorb up to 2 terawatts (TW,