Thin section image of a classic layered sequence from the Rum layered Intrusion. The way up is peridotite (multicoloured) at the top and anorthosite at the bottom. The band of opaque phase crossing the center of the sample is a chromitite band. Injection of a slug of picritic magma, plus magma mixing or incorporation of more silicic rock pushed the magma composition into the chromite stability field and casused precipitation of the chromitite layer.