IR spectra of basaltic mixtures [BAS] at different grain sizes in different proportions with synthetic amorphous carbon [SAC]. Top left panel: <50 µm; top-right panel: 50–200 µm; bottom-left panel: 200–500 µm; and bottom-right panel: 500–1000 µm. The mixture with different proportion of SAC are represented in each panel with continuous line with dash marker (0%), continuous line with a dot marker (1%), dashed line (5%), dashed-dotted line (10%), dotted line (30%), and pure continuous line (50%). The intensity scale is the same for each panel to enhance the difference in reflectance level among the four mixture combinations.