The 23 specimens on show represent all the types of ornamental stone (commercially known as “marble”) used to build Siena Cathedral (12-14th century). The dark stone is “serpentinite” extracted from various parts of Tuscany, whereas the “rosso ammonitico” comes from Gerfalco (Grosseto) and the true marbles come from the Montagnola Senese. Knowledge of the different lithotypes and their quarries of origin is essential for maintenance of the cathedral.