Why californium is worth more than gold: The science behind this million-dollar element

At today’s prices, one gramme of californium-252 can be valued at around $27 million, a figure that can exceed the value of roughly 200 kg of gold depending on where gold is trading. That headline comparison sounds like internet trivia, but the reason is straightforward: gold is mined at scale, while californium is manufactured in microscopic quantities inside nuclear reactors, for a handful of specialised uses that few other materials can match.

Gold is expensive because it is scarce, globally traded, and widely demanded. But it is still a natural commodity with a mature supply chain. Californium is different. There is no natural deposit you can mine. To obtain it, you have to make it.

The isotope most often discussed in price comparisons is californium-252 (CF-252). It is produced by irradiating heavier elements (typically starting from curium) in a high-flux nuclear reactor so they capture neutrons over time. This is not a one-step process. It can take months of reactor time, and then the material has to be chemically separated and purified from intensely radioactive mixtures. The yield is tiny, which is why global production is usually measured in milligrams, not grammes or kilogrammes.

That supply bottleneck is a major driver of cost, but it is not the only one. CF-252 also has a rare physical property: it is a compact, portable neutron source. It undergoes spontaneous fission and releases a strong neutron flux without needing a reactor to be running. That matters because neutrons are hard to generate conveniently. If you need them in a small device, in the field, or in an industrial setting, options are limited.