Marathon Fusion says its laboratory experiment beat CERN’s gold-production benchmark by a factor of 10, but the company has yet to disclose how much gold it actually made.
The San Francisco startup announced on Wednesday that it had converted mercury into stable gold using fusion neutrons during an experiment the previous month. It also reported producing radioactive copper isotopes from zinc.
Both are company-reported results, with no independently validated experimental yield available in the material reviewed.
CERN provided a more explicit comparison in May 2025. Its ALICE collaboration measured a maximum production rate of approximately 89,000 gold nuclei per second during lead-ion collisions. Across four Large Hadron Collider experiments between 2015 and 2018, an estimated 86 billion gold nuclei were produced, equivalent to just 29 picograms.
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Those nuclei fragmented almost immediately. Marathon claims to have produced stable gold-197 instead, through a different process that converts mercury-198 into mercury-197 before radioactive decay creates gold.
The commercial stakes are larger than the laboratory record. On its website, Marathon models annual revenue of $223 million from electricity alone at a gigawatt-scale fusion plant, rising to $482 million when gold production is included. The implied $259 million increase depends on assumptions about output, prices, and the feasibility of operating a commercial reactor.
Its July 2025 research projected roughly two metric tonnes of gold annually per gigawatt of thermal fusion power.
The missing data from October’s demonstration include a measured gold mass, isotope purity, recovery efficiency, and cost per gram. Without those figures, the reported experiment cannot establish whether artificial gold is a viable source of revenue, much less whether it could affect conventional gold supply.
Marathon’s nearer-term business is aimed at medical isotopes. It says its neutron experiments have already produced radioactive copper from zinc, while research published in December 2025 modeled ways to manufacture molybdenum-99 using small fusion systems operating below energy breakeven.
The company’s February 2026 paper estimated value per fusion neutron at around $10^-20 for gold or electricity and approximately $10^-10 for actinium-225, an isotope being developed for targeted cancer treatments. Those are modeled valuations, not realized sales or margins.
Marathon joined the Canadian Nuclear Isotope Council in July, connecting it with an established medical-isotope industry.
For now, the company’s most relevant proof point is not whether gold can be created. It is whether its reported transmutation results can be converted into measurable, recoverable output at a cost customers can justify.
