The Earth’s earliest continental lithosphere comprises two components: a dominantly felsic continental crust and a cratonic lithospheric mantle. However, whether those result from a process of differentiation from the primitive mantle or are two distinct components deposited, possibly hundreds of millions of years later, is still unknown. Metal stable isotope ratios are sensitive to magmatic processes but compared to radiogenic isotope ratios that have been widely used for the past decades to track crust-mantle differentiation, stable isotopes do not evolve with time. As such, metal isotope ratios do not require a priori knowledge of the ages of the different terrestrial reservoirs and are direct witnesses of geological processes. They can be used for direct comparison between the mantle and the continental crust without age correction.