The compound is a colorless to white crystalline salt and is transparent over a wide range of wavelengths, with commercial uses in optics that are also used in space telescopes.

Magnesium fluoride is prepared from magnesium oxide with sources of hydrogen fluoride such as ammonium bifluoride, by the breakdown of it: Related metathesis reactions are also feasible: The compound crystallizes as tetragonal birefringent crystals.

The structure of the magnesium fluoride is similar to that of rutile,[4][5] featuring octahedral Mg2+ cations and 3-coordinate F− anions.

[citation needed] Magnesium fluoride is tough and polishes well but is slightly birefringent and should therefore be cut with the optic axis perpendicular to the plane of the window or lens.

[6] Due to its suitable refractive index of 1.37, magnesium fluoride is commonly applied in thin layers to the surfaces of optical elements as an inexpensive anti-reflective coating.