Identification of lead(II) sulfide and pararealgar on a 13th century manuscript by Raman microscopy

The in situ non-intrusive chemical analysis by Raman microscopy of a very rare, early 13th century, Byzantine/ Syriac Gospel lectionary implies that the serious pigment blackening of many hues and affecting most of the illuminations is caused by the degradation of lead white to lead(II) sulfide, and that pararealgar (As4S4) never previously identified on any manuscript was used throughout as a deep yellow pigment.