It's part of the waste from phosphate production, for one, about 1/3 of the supply of apatite, which is basically calcium phosphate, is calcium fluoro-phosphate, called "fluorapatite". Gypsum is the main byproduct, but when this fluoride containing variant of the mineral is used, the gypsum contains fluoride, and it is easily isolated then by adding sodium carbonate/hydroxide.
There may be other waste sources too, I'm not sure, I think it is also found often with uranium ores too. I'm pretty sure that it also comes a long in trace amounts in the fluoride, yay, uranium.
I don't think Al, as in aluminium, has anything to do with it though. The connection to aluminium is that fluoride and aluminium are synergistic together in our bodies, accelerating the damage caused by the aluminium.
oh, here it is:
After separation of the residue by filtering, pure gibbsite is precipitated when the liquid is cooled, and then seeded with fine-grained aluminium hydroxide. The gibbsite is usually converted into aluminium oxide, Al2O3, by heating in rotary kilns or fluid flash calciners to a temperature in excess of 1,000 °C (1,830 °F). This aluminium oxide is dissolved at a temperature of about 960 °C (1,760 °F) in molten cryolite.
https://en.wikipedia.org/wiki/Bauxite
It's related to Cryolite:
https://en.wikipedia.org/wiki/Cryolite
Cryolite (Na3AlF6, sodium hexafluoroaluminate) is an uncommon mineral identified with the once-large deposit at Ivittuut on the west coast of Greenland, mined commercially until 1987.[8]
Uses
Molten cryolite is used as a solvent for aluminium oxide (Al2O3) in the Hall–Héroult process, used in the refining of aluminium. It decreases the melting point of aluminium oxide from 2000 to 2500 °C to 900–1000 °C, and increases its conductivity[16] thus making the extraction of aluminium more economical.[17]
Cryolite is used as an insecticide and a pesticide.[18] It is also used to give fireworks a yellow color.[19]
There you go. Cryolite powder is dusted on grapes, and some other fruit I believe. This makes all forms of grape juice, including wine, quite rich sources of fluoride and aluminium.