In Table 2 we see that niobium is present in all of the rutile-containing layers and zirconium in two of them; thus it is plausible to attribute these elements to the same or a similar source. Furthermore, the presence of molybdenum and antimony in the yellow lead-chromate containing layer 7 suggests the presence of small amounts of the yellow–orange lead molybdate and lead antimonite.[22] However, no evidence could be found for this in the XRD patterns. It is also known that the alkaline-earth elements calcium and strontium, observed in layers 2 and 8, are encountered as minor components of barium sulfate where they substitute for barium in the barite crystal structure.