In both line and spot mode acquisition, the NIST610 calibrated ages of the mica RM were offset with respect to their expected ages by up to ~11 % (Fig. , Table ). This bias is in the order of magnitude that has been observed in other studies, where it is ascribed to matrix effects resulting from the use of a non-matrix matched primary reference material (e.g. NIST610 glass or pressed nanopowder Mica-Mg). It has been suggested to correct for that matrix-induced bias by co-analyzing a matrix-matched, i.e. crystalline mica with known age. We adapted this approach by calculating matrix correction factors (MCF):