Variation in isotopic composition and atomic weight of magnesium in selected magnesium-bearing materials (modified from [23, 43]). The δ26/24Mg measurements are expressed relative to the reference material DSM3 because many materials were measured relative to it . However, DSM3 is not recommended as the international measurement standard for the δ26/24Mg scale because the supply is exhausted. The δ26/24Mg scale and 26Mg amount-fraction scales were matched using data from . The expanded uncertainty in matching the atomic-weight and 26Mg amount-fraction scales with the δ26/24Mg scale is equivalent to 1.1‰.