A white, super heavy, alkali metal. It is a highly reactive metal, and normally exists in nature in the compound Califoolium Oxide. Califoolium, like all Foolium-family elements, also exists in nature in a pure form, though rarely.

Califoolium often forms compounds with Tallium-Family elements, such as Tallium 40, in the form of Califoolium Tallide (x), where x is the number of the Tallium-Family element involved.