Figure 6

Sant’Eligio . Polished cross section of a sample from a brown area. UV illumination (a). Photograph Opificio delle Pietre Dure. ATR-FTIR of fluorescent material at the interface with calcite crystals, showing main characteristic absorption bands for calcium carbonate (1400 cm⁻¹) and gypsum (3535, 3400, 1120 cm⁻¹), lipids (1720 cm⁻¹), and a shoulder at 1320 cm⁻¹ from calcium oxalate (b). Raman spectrum in the same area, detailing the band from weddellite (1478 cm⁻¹) and neighboring small band at 1439 cm⁻¹ from the marble (c). The main Raman bands for the marble (1086 cm⁻¹) and gypsum (1009 cm⁻¹) do not interfere with the identification of weddellite.