Tuffeau stone

The soft stone is extracted from numerous quarries and has made a major mark on the architectural landscape of the Loire and its tributaries — especially the valley's world-famous chateaux.

Over the millennia, sediment from the sea floor, comprising fossilized living organisms and sand particles, became compressed to form what is now known as Tuffeau stone.

It differs from genuine chalk by the presence of foraminifera and many remains of shells originally deposited in shallow water (between 2 and 20 meters) and subsequently agitated, near a coastline.

In contrast, true chalk is rich in another type of shelly micro-fossil, the coccolith, which was deposited in deeper (~ 200 meters), and quieter, water.

These artificial caves have long been used as human dwellings, as the indoor temperature is remarkably constant from summer to winter.