The most expensive thing in the world is the chemical element rubidium. The American Atomic Energy Association began to sell californium-252 isotopes to industrial and medical institutions in the early 1970s. It is precisely because this element is extremely small that the price is very expensive.

From 1970 to 1990, 150 micrograms of californium-252 was sold every year. Haire and Baybarz reduced californium (III) oxide with lanthanum metal in 1974, and made californium metal flakes with a thickness less than 1 micron for the first time.

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There is a very small amount of californium on the earth, which mainly occurs in uranium mines with high uranium content. Uranium undergoes beta decay after capturing neutrons, thus forming californium. Californium can also be found near facilities where it is used for prospecting or medical treatment. Californium is insoluble in water, but it will stick to the soil, so the concentration of californium in the soil can be 500 times higher than that in the water around the soil particles.

Before 1980, radioactive fallout from atmospheric nuclear tests was scattered in the environment, which contained a small amount of californium. The fallout from nuclear explosion radiation collected from the air has been found to contain californium isotopes with mass numbers of 249, 252, 253 and 254.

Scientists once thought that supernovae would produce californium, because the decay of supernova material accords with Cf's 60-day half-life. However, the following research failed to detect the californium spectral line, and it is generally believed that the light curve of supernova accords with the characteristics of nickel -56.