The aim of this study is to investigate the\ud
provenance of marbles used as architectural elements\ud
(bases, shafts and capitals of columns) for building the\ud
internal spiral staircase of the medieval bell tower of St.\ud
Nicholas Church at Pisa, Italy. Accordingly, the 45 collected\ud
marble samples have been analysed by optical\ud
microscopy, X-ray powder diffraction and mass spectroscopy\ud
for carbon and oxygen stable isotope ratio analysis;\ud
additionally, SEM–EDS analysis have been\ud
performed to complement data about accessory minerals.\ud
By comparison with literature data on the main sources of\ud
the white Mediterranean marbles used in ancient times, the\ud
results show that the analysed samples are mainly white\ud
crystalline marbles from Carrara (Italy) and, subordinately,\ud
from other Tuscan and Eastern Mediterranean quarrying\ud
areas. In fact, Mt. Pisano and Campiglia M.ma (Tuscany,\ud
Italy) and Marmara (Turkey), Paros, Mt. Penteli, Thasos\ud
(Greece) are minor sources. The other coloured stones\ud
identified on the strength of their macroscopic features are\ud
quartzites from Mt. Pisano area and granitoids from Sardinia\ud
and Island of Elba (Italy). Occasionally, a very limited\ud
number of architectonical elements made up of\ud
Acquabona limestone from Rosignano Marittimo (Livorno,\ud
Italy), red limestone with ammonites (the so-called ‘‘Rosso\ud
Ammonitico’’) and black limestone belonging to the Tuscan\ud
Nappe sequence, outcropping at northwest of Pisa in\ud
the nearby Monti d’Oltre Serchio area, are present