Fig. 7

a Raman spectra obtained from a blue painted area on the Ottoman stone inscription AI198 and a reference sample of pure ultramarine pigment (characteristic vibrational bands at: 549 and 584 cm⁻¹). b Raman spectrum from a light green area on the Ottoman stone inscription AI244, showing bands of chrome yellow (359 and 840 cm⁻¹) and Prussian blue (277, 527 and 2149 cm⁻¹). The spectrum of pure Prussian blue is shown for comparison