Magnesium Fluoride

Magnesium Fluoride is a white or colorless inorganic chemical compound that is soluble in nitric acid and insoluble in alcohol and water. This material can be found in nature as the mineral sellaite.

Glass, Optical
As an optical material, magnesium fluoride exhibits transparency across a very wide range of wavelengths and has a low refractive index just below that of lithium fluoride.
Used in the production of optical coatings, glass, lenses, cathode ray fluorescent screen material, and other optical components.

Additional Notes:
*Along with lithium fluoride, magnesium fluoride is one of the materials that will transmit in the vacuum ultra violet range.
*This is a birefringence material, which means that its refractive index is dependent on the polarization and propagation direction of light.
*Magnesium fluoride is used to make telescope lenses.