On the basis of modern colloidal geoechemistry and taking into account the foundations of the physical chemistry of surfaces, a new theory of the origin of the Earth's continental crust is proposed. According to this theory, the formation of the sialic crust of the Earth involved a creaming process ensuing from the spontaneous emulsification of the "truly primitive" basic magma. In this theory the basic magma is considered as an initially simple and homogeneous fluid characterized by density fluctuations in critical conditions. Under certain circumstances immiscible nuclei of a new phase originate in the primitive magma ocean. This new liquid phase has a more acidic composition than the surrounding basic magma. As the phase separation proceeds the magma will comprise immiscible sialic portions in a state of dispersion. Under a decreasing shear rate, these portions progressively aggregate between themselves by coalescence to form larger blobs and successively these blobs, by coalescence, give origin to larger spherical bodies and so on, up to obtain, hierarchically, large enough dimensions. When the differentiated phase is very concentrated, the sialic blobs first distort, then markedly elongate and neck in to give an inverted layer: the segregated matter is forced out as a gel phase and forms the stable sialic protocrust. The rheologic behaviour of the differentiated portions is here illustrated by a model of three types of particles: primary tactoids, spherical clusters and aggregates. In addition, the general form of the curve of potential energy as a function of interparticle separation is used to illustrate the sequence of the events which in time led, as a result of cooling, to the formation of the earliest continental crust: stable magma emulsion → phase separation → metastable immiscibility → phase inversion → stable segregate → close packing → syneresis and accretion → crystallization.