The Loire region of France (Fig. 1) is famous for its many chateaux which represent not only a pinnacle in art and architecture but also are a testimony to the excellence of the local building stone. The Saumur region of the Loire valley has an estimated 1000 km of quarried limestone galleries which were excavated from the 1lth to the 19th century. The stone has been used in buildings ranging from grand chateaux to simple domestic, commercial and agricultural buildings (Bailey 1993) (Fig. 2).
The stone is extracted from thickly bedded, fine-grained Cretaceous limestones of Turonian age, mainly the Tuffeux Jaune of the Upper Turonian or the Craie Micacée of the Middle Turonian (Alcaydé et al. 1976). It owes its wide usage to the fact that it has ideal engineering properties for a dimension stone since it is stronger and more resistant to weathering than ordinary Cretaceous Chalk but not so strong as to be difficult to quarry or carve into decorative features. The stone occurs in deposits with widely to very widely spaced bedding and joint discontinuities which enable it to have been mined in a manner similar to that of the Jurassic, Bath Stone of England.The value of the stone does not lie solely in its architectural or constructional attributes. The abandoned mines remain as very stable underground spaces by virtue of their exceptionally wide bedding and joint spacing. They are relatively dry and, in common with most underground spaces, possess a constant temperature. Thus, they have found