“A San Francisco startup says it has pulled off the alchemist’s oldest dream: turning mercury into real, stable gold.

Marathon Fusion says it did it in September with fusion neutrons, at ten times a record CERN set in 2025.

Here’s the trick. Deuterium-tritium fusion fires out fast neutrons. When one slams into mercury-198, it knocks a neutron loose, leaving mercury-197.

That’s unstable, and over a few days it decays into gold-197, the only stable form of gold.

Marathon posted a gamma-ray readout showing mercury-197’s fingerprint, the gold on its way.

But here’s the catch. The company hasn’t said how much gold it made, and nobody outside has checked the data.

For scale, CERN’s collider made about 29 trillionths of a gram of gold in four years. Ten times tiny is still tiny.

The real goal is scale. Marathon’s 2025 paper, still not peer reviewed, says a big fusion plant could make tonnes of gold a year, roughly doubling its revenue.”

From Interesting Engineering.