exsolution

CONT: Lorsque la température retombera, la solution solide deviendra instable, il y aura précipitation d'un autre composé : exsolution.
CONT: [...] des phénomènes d'exsolution, marquant en principe, une certaine contemporanéité des cristallisations, peuvent se traduire par la formation concomitante de cristaux automorphes et xénomorphes.

CONT: ... segregations of relatively Na-rich feldspar develop within a relatively K-rich phase (or vice versa, depending on bulk composition). If equilibrium cooling proceeds far below the critical temperature, the segregations become progressively more Na-rich and the host more K-rich. This exsolving process of Na-feldspar from K-feldspar produces the group of alkali feldspars known as ""perthite."" ... Although most perthites probably form by exsolution, replacement and simultaneous crystallization have also been advanced as modes of perthite development.
OBS: ... the relationship between the exsolution process and the onset of ordering is not understood and some lines of evidence suggest that ordering preceded exsolution.