Honey has a natural trend to crystallize. The crystallization of honey has nothing to do with its quality. In a jar full of honey, crystals begin to form first at the bottom and then at the rest of the vase. New crystals will be added daily and that gives a non-pleasant look to the honey. Crystallization makes honey difficult to use, as well. But, crystallized honey keeps all its properties.
In case that your favorite honey crystallizes, do not worry! On the contrary, you should be glad that you have bought an excellent honey (impure honey does not crystallize). Crystallized honey can be reset to its original state by using a moderate heated bain-marie. Just heat up the honey and it will be th same as when you bought it. One may also leave the honey vase to heat up on a heating radiator for a few minutes, it will be fine.