This alloy is typical of many copper based alloy systems. The dendrite structure shows coring (variation in solute concentration). The light areas are rich in nickel and the darker areas are low in nickel. Chill casting extracts heat quickly enough to prevent significant solid state diffusion, resulting in cored dendrites. The centres of the dendrites that cool near the liquidus temperature, are nickel rich compared to the outer layers that solidify at progressively lower temperatures. Because the partition coefficient is positive the outer layers solidify with progressively lower nickel concentrations. The observed pattern results from the intersection of the plane of polish and the randomly orientated regions of equal solute concentration.