‘GRANITO DEL FORO’ AND ‘GRANITO DI NICOTERA’: PETROGRAPHIC FEATURES AND ARCHAEOMETRIC PROBLEMS OWING TO SIMILAR APPEARANCE

Abstract

Granitoid rocks were among the stone materials most frequently used for columns and pillars during the Roman period. When employed in Rome and the Mediterranean provinces, they were mainly quarried in Egypt, in Asia Minor and in Italy. Some of these rocks show very similar macroscopic features, so it is often very difficult to tell them apart with the naked eye. This is the case with the ‘Granito del Foro’ (or Marmor Claudianum), from the Gebel Fatireh, in the Eastern Desert, and the ‘Granito di Nicotera’ (Calabria), both exploited from the first century ad onwards. Both feature medium grain size and a white‐greyish colour with black patches. In order to obtain a certain microscopic and geochemical discrimination of these rocks, and to provide the first known petrographic classification of the ‘Granito di Nicotera’, a comprehensive mineralogical, petrographic and geochemical investigation was performed on several samples from the quarry. The results were compared with the corresponding data known for Marmor Claudianum in the literature. Good discrimination between the granites is possible, mainly on the basis of modal mineralogy and geochemical characteristics. The ‘Granito del Foro’ contains hornblende, while the ‘Granito di Nicotera’ contains muscovite, and has a distinctive peraluminous index and trace element abundances.