Marathon Fusion Says It Turned Mercury Into Gold With Fusion Neutrons

On October 21, 2026, fusion-energy startup Marathon Fusion announced on the social platform X that it had converted mercury into stable gold using neutrons produced by nuclear fusion. The San Francisco-based company said the achievement came at a production rate ten times higher than CERN's 2025 record, according to Glitchwire's review of the company's post.

In its post, Marathon Fusion described the result as turning mercury into real, stable gold at a rate ten times faster than CERN's 2025 figure, Glitchwire reported after reviewing the announcement. The company did not publish supporting data alongside the claim.

How the mercury-to-gold process is supposed to work

According to Glitchwire's review of the claim, the method starts with mercury-198, an abundant stable isotope. Fast neutrons generated by deuterium-tritium fusion strike the mercury and knock out a neutron, turning it into mercury-197. That isotope then decays into stable gold-197, with a half-life of roughly 64 hours, Glitchwire reported. The Conversation added that neutrons above 6 million electron volts are needed to trigger the transformation.

Euronews reported that, according to the company's own study, gold made this way would initially be radioactive and would need to be stored for up to 18 years before it could be sold safely.

Comparing the claim with CERN's gold

What the company has not shown

• No independent, peer-reviewed confirmation of the October claim has been published, according to The Conversation and Glitchwire.
• Marathon has not disclosed the total amount of gold produced, its isotopic purity or the efficiency of the conversion process, Glitchwire reported after reviewing the company's announcement.
• No commercial fusion power plant exists anywhere to test whether the economics in Marathon's modeling would hold up in practice, The Conversation noted.
• The company's planned test reactor in San Francisco is rated at about 1 kilowatt of fusion power, a small fraction of the gigawatt scale used in its commercial projections, according to Glitchwire.

Why transmuting gold has long been difficult

The Conversation noted that at CERN's rate of about 29 picograms of gold over four years from lead-ion collisions, producing a single troy ounce would take roughly hundreds of times the current age of the universe. Fusion neutrons are considered a more promising route than particle collisions because they can trigger the needed decay sequence in mercury more efficiently, but doing so still requires neutron fluxes and reactor conditions that have not yet been demonstrated commercially, the outlet reported.

Who is behind Marathon Fusion

Marathon Fusion was founded in 2023, according to Glitchwire. The company raised at least $6 million in seed funding, with investors including the 1517 Fund, mining company Anglo American and Breakthrough Energy, Glitchwire reported. Glitchwire added that the U.S. Department of Energy's ARPA-E program provided $449,065 for related fuel-cycle research between 2023 and 2025.

Could lab-made gold affect prices?

Euronews drew a comparison to the market for lab-grown diamonds, whose wholesale prices fell 90–95% from 2015 levels once synthetic stones reached volume production. Unlike diamonds, the outlet noted, fusion-made gold would be chemically indistinguishable from mined gold once its radioactivity decays. However, Euronews also reported that no commercial fusion plants currently exist, meaning any effect on gold markets remains theoretical for now.