δ-MgCl2 has relevant applications in the field of electrochemical energy storage and Ziegler–Natta catalysis. Here, we clarify the short-range structural peculiarities that make the disordered phase δ-MgCl2 extremely chemically active relative to the higher lattice energy phases, α-MgCl2 and β-MgCl2. X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and nuclear magnetic resonance (NMR) results are included. These findings, demonstrate the existence of [MgCl2] n nanoribbons and active nanosurfaces in δ-MgCl2 and provide new insight about the nature of the bonding in the allotropic forms of MgCl2.