Fig. 3
a Photographs of both sides of the flat pebble from layer RGS2 (square C4d); b characteristic Raman spectra obtained on the pebble: (A) amorphous carbon, (B) haematite, (C) manganese oxide, (D) quartz, (E) maghemite mixed with manganese oxide and (F) goethite and anatase (144 cm−1); c high magnification image of brown and beige residues and d high magnification image of beige, black and white residues