Californium was first made in 1950 at Berkeley by Stanley Thompson, Kenneth Street, Albert Ghiorso and Glenn Seaborg, by bombarding curium with alpha particles. It was named after the state and university of California. Californium is a silvery, radioactive metal and a prodigious emitter of neutrons, a property that gives it real practical uses in starting nuclear reactors, in detecting gold and oil in boreholes, and in a form of cancer radiotherapy. A single microgram of californium-252 is an intense neutron source, so that this vanishingly rare, laboratory-born metal earns a genuine place in industry and medicine, and it also serves as a target for attempts to synthesise still heavier elements.
A single gram of californium-252 has been priced at tens of millions of dollars, making it among the most valuable materials by weight ever produced, though in practice only microgram quantities are made at a time. Its intense, steady stream of neutrons is used to activate oil-bearing rock in borehole logging, revealing the presence of hydrocarbons and moisture from the pattern of radiation the rock reflects back. The same neutron-rich property also makes small californium sources useful for starting up nuclear reactors, providing a reliable initial burst of neutrons to begin the chain reaction cleanly.