Honeys over time will crystallise, process where the honey appears to be thickened, become lumpy and grainy. Often referred to as granulation. Its a natural phenomenon by which honey turns from a liquid to semi-solid state.

Crystallization by no means changes the quality of your raw honey, or mean it is off. It only affects the colour and the texture (slightly grainy). Crystallization of your honey is an attribute of pure natural honey.

Raw honey is highly concentrated sugar, meaning that water in your honey contains much greater amount of sugars than it can naturally dissolve. Crystallization is an absolutely natural phenomenon which occurs when glucose separates from water, , after which glucose remains in the form of crystals.
There are two main types of sugars in the carbohydrate composition of honey, these are fructose and glucose. Generally, fructose ranges from 30 to 44%, and glucose from 25% to 40%. Glucose is the underlying cause of crystallization as its lower solubility compared with that of fructose.