3.1.2. BSE Map

Several fields of the BSE map from Boliden AB showed a shift in brightness and contrast to the surrounding fields which was not observed in the CSM map (Figure 5). This potentially indicates a poor vacuum condition in the SEM chamber during measurement, or beam fluctuation; however, no impact on the mineral map was observed.

**Figure 5.** BSE image and corresponding mineral map of a part of the thin section analyzed in this study for CSM (left) and Boliden AB (right). A grey-level shift in the BSE image of Boliden AB can be observed (indicated by arrows). This shift was not observed for CSM and is not reflected in the mineral map.
