Why is fluorine not found freely in nature?

Fluorine is not found in its free state in nature because it is the most electronegative and powerfully oxidizing element known. Because of its extreme chemical reactivity, no other substance in the natural environment is capable of oxidizing the fluoride anion back into the free element.12

Instead, fluorine exists exclusively in the form of chemical compounds, such as fluorite, cryolite, and fluoroapatite. While trace amounts of the free element can occasionally be found in fluorspar that has been subjected to radiation from radium, these are rare exceptions. Due to its high reactivity, fluorine readily combines with almost all other elements to form stable ionic or covalent fluorides.31