Why the moisturiser cream is grainy?

Why the moisturiser cream is grainy?
Shea butter is one of ingredients of the moisturiser cream. Sometime, as we melt Shea butter the linolenic, arachidic and linoleic acids melt very quickly. They are actually responsible for the slightly ‘moist’ quality of the butter. You can imagine if they all melt at different rates. So the butter also solidify at different rates as it cooled. As result when is the butter slowly cool these fractions stay separate causing the cream to go grainy.