Fractional crystallization

Fractional crystallization changes a residual geological melt by removing crystals as they form. Different minerals accept different elements into their structures, so the removed solid generally has a different composition from the remaining liquid. Successive removal can progressively enrich components that enter the early crystals weakly.

Settling, flotation or flow through a crystal-rich region can separate the phases. The resulting cumulate rock and residual melt need not have the same bulk chemistry. This is a cooling and separation process; partial melting instead starts by producing liquid from an incompletely melted rock.