In this study, we define accuracy as the degree of similarity between the measured ages and the expected ages, quantified as the relative deviation in percentage. For all mica RM investigated in this study, high-precision ID-TIMS data is available (Table ), providing reliable expected ages. In all spot ablation sessions, an improved accuracy of < 3.0 % is obtained for dating of Harvard 98987 muscovite (-0.1 -2.9 %) and SagaB biotite by applying a Phalaborwa biotitebased MCF (Fig. , Table ) compared to the accuracy obtained for non-matrix matched ages (-3.7 % to -11.05 %). In the case of MicaMg-pressed nanopowder, the matrix correction has the opposite effect and leads to a decrease in accuracy from < 2.6 % (without matrix correction) to < 9.1 % (with Phalaborwa-based matrix correction). This observation supports earlier conclusions on the general matrix mismatch between crystalline mica and pressed mica nanopowders. For line scan ablation-based age determinations, application of a Phalaborwa biotite-based MCF leads to a good accuracy for SagaB biotite (-0.8 -1.4 %, Fig. , Table ), whereas for Harvard 98973 muscovite, the accuracy even decreases compared to the non-matrix corrected ages (from 2.7-3.7 % to 11.3.-11.4 %). This implies that both a structural AND a chemical matrix match between the secondary mica RM and unknown sample material are crucial to somehow different to spot mode ablation, where accurate ages seem to mainly rely on a structural matrix match, i.e. muscovite secondary RM can be equally well used for matrix correction of biotites (Fig. ).