If you need to ask, you probably can't.
Californium is an extremely rare element produced in "atom smashers". If that doesn't suggest some possible sources to you, you don't have any business having any.
Not californium, but neutrons emitted by californium.
All the isotopes of californium are radioactive, artificial and unstable.
Californium is radioactive and a strong neutrons emitter; californium can be lethal.
Californium has 98 protons.
Californium is a metal.
Californium is not flammable.
Californium is a metal.
Californium is not crucial.
Californium is not flammable.
Californium is not flammable, as it is a radioactive metal that does not support combustion.
Californium is a soft metal.
Californium is a metal !