Fig. 3

a, b STEM-BF image and chemical distribution maps for Fe (green), Pb (blue) and Si (red) of an alteration halo containing dendritic growth/dissolution features; c TEM image of latches of Zn-rich magnetite within the branches of the dendrites; the location of the crystal shown in d is encircled; d high-resolution TEM image of a Zn-rich magnetite crystal; a predominant crystal face and the direction of growth are labelled accordingly; e remnants of a micrometer size Zn-rich magnetite crystal along the surface of the FIB towards the Pt-glue; the area shown in f is indicated with a black square; f agglomeration of spherical Zn-rich magnetite nanoparticles along the rims of the latter crystal; orientation of the lattice fringes parallel to (311) are highlighted with white lines