US start-up claims it turned Mercury into Gold, beats CERN’s 2025 record

Marathon Fusion, a San Francisco-based fusion start-up, claims to have turned mercury into stable gold using fusion-generated neutrons. The method turned the production rate 10 times higher than the record set by CERN in 2025. However, the company has not yet revealed the amount of gold produced during the experiment.

The company's latest claim couldn't be verified in the available information, and Marathon Fusion has also not shown a process that could produce gold economically. In addition, the company is also planning to come up with another application for its technology, including producing medical isotopes used in cancer diagnosis and treatment.

How mercury turned into gold?

In the nuclear transmutation process, an atom's nucleus is changed to produce a different element or isotope. Unlike a chemical reactions simply rearranges atoms, leaving their nuclei untouched, nuclear transmutation goes further, it alters the nucleus itself.

Marathon Fusion’s approach relies on high-energy neutrons produced by a deuterium-tritium fusion reaction to convert mercury-198 into mercury-197, an unstable isotope. That radioactive mercury-197 then undergoes electron capture, decaying into gold-197, gold’s only stable isotope.

The process unfolds in three stages. It begins with mercury-198, a stable isotope found in nature, as the raw material. Then next, Neutrons generated through fusion are then used to trigger the nuclear reaction that turns this into mercury-197. Finally, the mercury-197 decays into stable gold-197, though the method still has to contend with radioactive byproducts generated along the way.

Back in May 2025, scientists at CERN’s Large Hadron Collider confirmed they had generated gold nuclei by colliding lead nuclei. According to estimates from CERN’s ALICE experiment, around 86 billion gold nuclei, amounting to roughly 29 picograms of gold, were created across four major experiments during the collider’s run between 2015 and 2018. However, these nuclei survived for only a fleeting moment before disintegrating.

Marathon Fusion is taking a different route. Rather than relying on lead-ion collisions as CERN did, the company plans to harness neutrons generated through fusion to produce gold, using a method intended to scale up output significantly.