Californium — USD27 juta atau Rp355 miliar/gram.
The most expensive chemical element ever synthesized only once since its discovery in 1950. Californium 252 is one of the most commonly used radioactive substances to produce gamma radiation. In the military field, Californimum 252 is usually used for explosives detection devices, mines, and unexploded cannon balls. Other uses of the gamma radiation of Californium 252 are as nuclear reactors