Marathon Fusion Claims It Turned Mercury Into Stable Gold Using Fusion Technology

San Francisco-based fusion startup Marathon Fusion says it has successfully transformed mercury into stable gold atoms using fusion-generated neutrons. The company announced the claimed experimental breakthrough on October 21, 2026, describing the result as “high-rate alchemy” and claiming a production rate 10 times the record reported by CERN in 2025. However, Marathon has not publicly disclosed the quantity of gold produced, and the result has not been independently verified.

The announcement builds on research Marathon published in 2025 proposing a way to produce gold inside future fusion power plants. The method uses nuclear transmutation to convert mercury into a radioactive isotope that subsequently decays into stable gold. If the process can eventually be engineered at industrial scale, it could create a valuable byproduct for fusion reactors. For now, the reported experiment is a claimed scientific milestone, not proof that commercially viable gold production is possible.

Key Takeaways

• Experimental claim: Marathon Fusion says it converted mercury into stable gold using fusion-generated neutrons.
• 10-times comparison: The startup claims its production rate exceeded CERN’s 2025 gold-production record by a factor of 10, although the two results have not been independently shown to be directly comparable.
• Nuclear transmutation: The proposed process converts mercury-198 into mercury-197, which decays into stable gold-197.
• Commercial potential: Marathon’s earlier research estimated that a future fusion plant could produce tonnes of gold annually, but those projections are not demonstrated commercial output.
• Major limitations: The quantity produced, production efficiency, operating costs and independent verification remain outstanding questions.
• Broader ambition: Marathon is developing fusion technology and exploring the production of medical isotopes alongside electricity generation.

What Did Marathon Fusion Announce?

On October 21, Marathon Fusion said it had demonstrated a process for turning mercury into stable gold. The startup also reported progress in isotope enrichment using a plasma centrifuge and said it was building a fusion reactor in San Francisco.

The announcement attracted attention because producing gold from another element has been a longstanding scientific and historical ambition. Unlike conventional chemical processes, which rearrange electrons and chemical bonds, the process described by Marathon changes an atom’s nucleus.

However, the company did not disclose how much gold its experiment produced or publish a complete set of detailed experimental results alongside the announcement. Its claim that the production rate exceeded CERN’s record by 10 times therefore requires careful interpretation.

CERN’s 2025 result involved gold nuclei produced during collisions involving lead nuclei in the Large Hadron Collider. Marathon describes a different process involving fusion-generated neutrons and claims to have produced stable gold. Without sufficiently detailed and independently verified measurements, the two results should not be treated as a straightforward comparison of commercially usable gold output.

How Can Mercury Be Turned Into Gold?

The process is called nuclear transmutation. An element’s identity depends on the number of protons in its nucleus. Changing the nucleus through a nuclear reaction can therefore transform one element into another.

Marathon’s proposed method follows a specific sequence:

1. Start with mercury-198: The process uses the mercury isotope mercury-198 as its starting material.
2. Expose it to high-energy neutrons: Neutrons generated by deuterium-tritium fusion reactions interact with the mercury nuclei.
3. Produce mercury-197: A nuclear reaction converts mercury-198 into mercury-197 by removing two neutrons.
4. Allow radioactive decay: Mercury-197 undergoes electron capture and becomes gold-197.
5. Process the material: Any resulting impurities or radioactive isotopes must be assessed and managed before the material can be used commercially.

Gold-197 is the only stable naturally occurring isotope of gold. The underlying nuclear physics is established, but using the process to manufacture meaningful quantities economically presents a much more difficult engineering challenge.

How Does This Compare With CERN’s Gold Production?

In 2025, CERN reported that its Large Hadron Collider had produced gold nuclei during high-energy collisions involving lead. According to reporting on the ALICE experiment, the total was approximately 29 picograms over the collider’s 2015–2018 operating period.

That quantity is extraordinarily small. The gold nuclei existed only briefly before being destroyed in subsequent collisions with accelerator equipment or other interactions.

Marathon claims its fusion-based approach can produce gold at a rate 10 times higher than CERN’s record. But the comparison needs context: the experiments use different mechanisms, and the company has not disclosed enough information to establish how much stable gold it produced or whether the claimed rate is comparable under equivalent measurement conditions.

Factor	CERN’s reported result	Marathon Fusion’s claim
Method	High-energy lead-ion collisions	Fusion-generated neutrons acting on mercury
Gold production	Tiny quantities of gold nuclei	Experimental conversion into stable gold claimed
Reported scale	Approximately 29 picograms across the cited collider run	Total quantity not publicly disclosed
Verification	Reported through CERN’s ALICE experiment	Independent verification outstanding
Commercial production	Not intended as a gold-manufacturing process	Future industrial application remains unproven

The comparison is scientifically interesting, but it does not establish that Marathon can produce gold at a commercially competitive price.

Could Fusion Reactors Produce Tonnes of Gold?

Marathon’s 2025 research paper, titled Scalable Chrysopoeia via (n, 2n) Reactions Driven by Deuterium-Tritium Fusion Neutrons, proposed integrating mercury into a fusion reactor’s neutron-multiplying blanket.

Using nuclear simulations, the researchers estimated that a suitable system could produce more than two tonnes of gold per gigawatt of thermal power annually. The company’s earlier public estimates also described potential production of around five tonnes per gigawatt of electrical capacity per year under a proposed plant configuration.

These are model-based projections, not evidence that an operating commercial fusion reactor can produce those quantities.

Several engineering challenges remain:

• Fusion power: The approach depends on developing a functioning fusion system capable of operating at commercial scale.
• Isotope purity: The starting material and resulting reactions affect the isotopes produced and the potential for radioactive contamination.
• Radiation management: The material may require processing, monitoring and storage before it meets safety requirements.
• Economic feasibility: Producing gold is useful only if the combined costs of the reactor, materials, separation and processing make financial sense.
• Independent validation: Experimental measurements must establish production rates, purity and efficiency.

The proposal is therefore best understood as a potential additional revenue stream for future fusion plants, rather than an imminent alternative to conventional gold mining.

Why Marathon Fusion Is Also Interested in Medical Isotopes

Gold is not the startup’s only interest. Marathon has also discussed producing medical isotopes that could support imaging and targeted cancer treatments.

Its research and development work includes methods for producing isotopes such as copper-64 and copper-67 from zinc through neutron irradiation. These isotopes have applications in medical imaging, radiopharmaceutical research and the development of targeted therapies.

The company has also described work involving actinium-225, a radioactive isotope being investigated and used in targeted alpha therapies for certain cancers. Such applications could be valuable because supplies of some medical isotopes are limited by the specialized infrastructure and processes required to produce them.

Medical-isotope production is a separate technical and commercial challenge from gold transmutation. Each isotope has its own production requirements, safety considerations, processing needs and regulatory pathway. Marathon’s broader strategy is to explore whether fusion-related neutron technology can produce valuable materials alongside its longer-term power-generation ambitions.

Could Lab-Made Gold Affect Gold Prices?

Not in the immediate future based on the evidence currently available.

Even if Marathon’s experimental claim is validated, the company would still need to demonstrate that its process can produce meaningful quantities safely, reliably and economically. Its earlier estimates depend on future fusion infrastructure that has not yet been demonstrated at commercial scale.

Gold’s market value is influenced by factors including investment demand, central-bank purchases, jewellery consumption, industrial uses, mining supply and recycling. A new production method could eventually affect supply, but only if output becomes sufficiently large and economically competitive.

The ability to manufacture an element is not the same as the ability to manufacture it cheaply. Scientists have produced gold through nuclear reactions before, but previous methods have not provided a commercially viable alternative to mining.

Marathon’s claim could become significant if its method proves scalable and compatible with a commercially successful fusion reactor. Until then, predictions that lab-made gold will disrupt bullion prices are speculative.

The Bigger Picture

Marathon Fusion’s announcement brings together two ambitious scientific goals: developing commercial fusion energy and using nuclear reactions to manufacture valuable isotopes. The company’s proposed approach is notable because the same neutron environment that a fusion reactor needs could potentially be used to produce additional materials, creating another possible source of revenue.

But the distinction between a claimed experiment, a validated production process and a commercially viable industrial system remains crucial. Independent confirmation, transparent measurements and evidence of practical scalability will determine whether the latest announcement represents a major advance or an early step toward a much longer engineering challenge.

FAQs

1. Has Marathon Fusion really turned mercury into gold?

The company says it demonstrated the conversion experimentally in an announcement dated October 21, 2026. However, the amount of gold produced has not been disclosed, and independent verification remains outstanding.

2. How does mercury become gold?

Marathon’s proposed process uses high-energy fusion neutrons to convert mercury-198 into radioactive mercury-197. That isotope subsequently decays into stable gold-197.

3. Did Marathon Fusion beat CERN’s gold-production record?

Marathon claims its production rate was 10 times CERN’s 2025 record. However, the methods differ, and publicly available information does not yet establish a directly comparable, independently verified production rate.

4. Could fusion reactors produce tonnes of gold every year?

Marathon’s research simulations suggest that a suitably designed future fusion plant could produce tonnes annually. This remains a projection rather than demonstrated commercial output, and the technology faces substantial engineering and economic challenges.

5. Will this breakthrough make gold cheaper?

There is no evidence that the announcement will materially affect gold prices in the near term. Commercial production would require reliable, large-scale output at a competitive cost, and no such capability has been established.

Looking Ahead

The next important milestone will be the release of detailed experimental evidence and independent scientific validation of Marathon Fusion’s reported results. Data on the quantity of gold produced, isotope composition, production efficiency and radioactive byproducts will help researchers assess the significance of the claimed breakthrough.

Over the longer term, the company will need to demonstrate that its technology can be integrated into a functioning fusion system and operate economically at scale. If those challenges can be overcome, transmutation could become a valuable complement to fusion electricity and medical-isotope production. Until then, turning mercury into gold remains a scientifically plausible nuclear process with an unproven commercial future.