What is a key example of secondary differentiation happening within the core over billions of years?

Answer

Lighter elements dissolved in the liquid outer core precipitate out onto the solid inner core

Secondary differentiation involves slow changes within established layers. In the core, this includes the precipitation of lighter elements onto the inner core, gradually purifying it over geological timescales.

What is a key example of secondary differentiation happening within the core over billions of years?
compositionlayerprocessdensityplanet