tuffeau, a common rock type in the central loire. Tuffeau blanc is calcareous but provides much better drainage than most limestones. This is the rock used to build many of the châteaux of the Loire and remaining hollows in the rock have been adapted for winemaking and storage. The overlying tuffeau jaune is more sandy, and is particularly suitable for the Cabernet Franc vine, underlying some of the best vineyards in chinon and saumur-champigny. It is distinct from both tufa and tuff.