Fig. 3

Optical microscopy (OM). Photo in polarized light of a subsample of KLR-2369/P2 mounted edge-on–the surface being at the top of the pictures. a: Two brown stained layers, each of ca. 50 µm thick, are visible at the top; followed by a layer appearing white in the polarized reflected light; finally at the bottom the marble substrate appearing grey. Two Laser ablation tracks made with a beam diameter of 50 µm are slightly visible as indicated by two white arrows. b: magnified detail showing the two brown stained layers and featuring several red and dark brown grains of up to a few microns in size; c: further magnification showing a difference in size distribution of both the red and dark brown pigments