“Last month, we demonstrated high-rate alchemy: turning mercury into real, stable gold, beating CERN’s record by a factor of 10,” the startup said in a social media post on October 21. San Francisco startup Marathon Fusion claims it has turned mercury into real, stable gold.
The company said its production rate was 10 times a benchmark set by CERN in 2025, although it did not disclose how much gold it made. In the post on X on October 21, Marathon Fusion wrote, “We’ve reduced alchemy to a series of difficult but tractable engineering problems. The company shared gamma-ray measurements that it said showed the presence of mercury-197 and gold-197 after irradiation. These neutrons interact with mercury-198, a naturally occurring stable isotope, to produce radioactive mercury-197. The mercury-197 then decays into gold-197, the stable isotope of gold . (Also read: Norwegians fall for wild investment scam: Buying gold and leaving it in the forest ) In a 2025 paper, Marathon Fusion proposed placing mercury in a blanket surrounding a fusion reactor’s core.
The company’s proposed process uses high-energy neutrons produced by deuterium-tritium fusion. The company estimated that a plant producing one gigawatt of thermal power could generate around two tonnes of gold annually. It argued that selling the gold could significantly increase the plant’s revenue without reducing electricity production or the reactor’s ability to produce tritium, a fuel used in fusion reactions.
