When Fe-containing Al–7Si–xMg alloys are solution-treated, usually as the initial stage of a T6 heat treatment, some of the π-Al 9 Mg 3 FeSi 5 phase present in the as-cast alloy transforms into fine needle-like intermetallic particles (as seen on a polished surface). These precipitated needles, speculated to be β-Al 5 FeSi phase, have not been definitively characterised to date. In this work, electron microscopy characterisation by various techniques was conducted to assess the nature (i.e. the composition, morphology and crystallography) of these particles to verify or otherwise the validity of the above hypothesis. It is found that the particles are indeed β phase platelets, of the same Al 5 FeSi or Al 4.5 FeSi stoichiometry as particles formed during solidification. Close observation of their crystallographic structure suggests fine-scale internal complexities in some of the particles.