Pigeonitic submicroscogic laminar (100) intergrowths, less than 1 thin, in a salite of composition En,,w~,,Fe,~ have been identified by electron microscopy and electron diffraction techniques. The parametres of the pigeonitic intergrowth were obtained from calibrated electron diffraction patterns, by wmparing the X-ray refined parameters of salite with those given by the electron diffraction patterns. We discuss the nucleation and growth mechanism of pigeonitic lamellae, and the thermal history of the whole rock, on the basis of these data and the images obtained by electron microscopy.