Krustenbildung, ein schützender und zerstörender Vorgang: eine Fallstudie am "Reials Col.legis" (16. Jahrhundert, Katalanien, Spanien) / Patination as a Constructive and Destructive Process: The Case of "Reials Col.legis" (16th Century, Catalonia, Spain).

The "Reials Col.legis de Sant Jaume i Sant Maties" (Tortosa, Catalonia) is one of the masterpieces of the Renaissance style and was built in the 16th century with dolostones and calcarenites relatively well preserved and which are coated by an orange to black continuous patina. By studying samples obtained from different rock substrate and orientations the building stones and the layers forming the patina have been characterized by using several techniques (XRD, SEM/EDS, optical microscopy). The data obtained allowed us to establish a common sequence for this patina which consists of two layers: one micritic and one gypsum-rich layer in which, occasionally, there is bioactivity present living in and on the patina and the underlying rock. An hypothesis of the development of the layers of the patina is proposed on the basis of their mineralogical and petrographical features.