According to Google..............

    What makes honey crystallize is due to the type of flower the honey bee visited when she gathered the blossom's nectar. The floral source determines whether the honey will turn into a solid form more quickly or not. Some honeys while raw will stay in a liquid form for quite a while. Other honeys will turn to a solid form with in a few weeks. This is due to how stable the sugar crystal is in the nectar.  Honey doesn't need to be stored in the refrigerator. This speeds up the crystal formation. 
    Storing your honey at room temperature will deter crystallization. Crystallization occurs most rapidly at cool temperatures (40º - 57ºF) therefore honey should never be stored in the refrigerator.
    Honey crystallization or granulation is its natural conversion from liquid state into crystalline solid without deterioration of its properties. The process of honey granulation can be explained by the fact that one of honey sugars-glucose is oversaturated. Honey fructose as a more soluble substance crystallizes slower.