The data are magnesium (Mg) isotope composition, i.e. the relative difference of isotope ratios as defined in Coplen (2011, doi: 10.1002/rcm.5129). The reference was DSM-3 (see Galy et al., 2003, doi: 10.1039/b309273a) and data are given in per mil. Samples consisted of terrestrial peridotites and basalts as well as a suite of meteorites including chondrites, shergottites, diogenites and one angrite. A large portion of the data have been published in Hin et al. (2017, doi: 10.1038/nature23899).