**6. Conclusions**

This study has demonstrated the potential of both SEM- and Raman-based mineralogical imaging for the characterization of iron oxide apatite deposits (IOA). In polished sections of IOA, magnetite, hematite, apatite, carbonates, and silicates were easily detected and mapped. The discrimination of magnetite and hematite, however, is strongly dependent on operating conditions in SEM-MLA. Raman imaging shows a major advantage due to distinct Raman spectra that enable in situ identification. Raman spectroscopy allows the determination of mineral composition and can detect contaminants in iron oxides, further advancing iron ore characterization. However, the main "struggles" of Raman are the time demands, especially when it comes to large volume or bulk analysis of iron ores. Further enhancement of the Raman technique is pursued for better characterization of iron ores.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/2075-163X/9/9/544/s1, Figure S1: Reference Raman spectra. Background-corrected and normalized Raman reference spectra used for linear combination.

**Author Contributions:** Conceptualization, P.K. and A.J.; software and methodology, S.G. and P.K. (MLA) and A.J. (Raman); investigation, P.K.; resources, P.K.; data curation, P.K.; writing—original draft preparation, P.K. and A.J.; writing—review and editing, all authors.; visualization, P.K. (MLA) and A.J. (Raman); supervision and project administration, T.S. and K.N.; funding acquisition, P.K.

**Funding:** This research is part of the author's doctoral study and fully funded by Luossavaara Kiirunavaara AB (publ.).

**Acknowledgments:** We thank Richard J. Best and Igor Zlotnikov (BCUBE Dresden) for the Renishaw Raman measurements. The kind help of Enrico Pigorsch (PTS Heidenau) with the WITEC Raman system is highly appreciated. Matthias Finger provided the SpectralImaging software and was helpful in analyzing the Raman data. Patrick Krolop gratefully acknowledges the funding and support of LKAB and involved personnel. Michael Stoll and Roland Würkert are thanked for sample preparation.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data, nor in the writing of the manuscript.
