  We study crystalline fluoride microresonators for mid-infrared applications.
Whispering gallery mode resonators were fabricated with BaF$_2$, CaF$_2$ and
MgF$_2$ crystals. The quality factors were measured at wavelengths of 1.56
{\mu}m and 4.58 {\mu}m. The impacts of fabrication technique, impurities,
multiphonon absorption and surface water are investigated. It is found that
MgF2 resonators have room temperature Q factor of $8.3\times 10^6$ at
wavelength of 4.58 {\mu}m, limited by multiphonon absorption.
