Tuffeau stone

Tuffeau is a marine sedimentary rock, found in the Loire Valley of France.

The Loire Valley formed the floor of a vast sea 90 million years ago. 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.

Mining of Tuffeau stone for construction reached its peak in the 15th century, and the mining techniques used to extract the valued stone created a vast network of caves along the banks of the Loire. The caves have been used as dwellings in the past, partly due to the practicality that the indoor temperatures are kept remarkably constant from summer to winter. Today, many of the larger caves are used for growing a wide variety of mushrooms, which are transported daily to the markets in Paris. The Loire is the largest supplier of mushrooms to Paris.

Today, a number of older dwellings, from the magnificent Château d'Ussé [http://en.wikipedia.org/wiki/Ch%C3%A2teau_d%27Uss%C3%A9] and Château de la Motte d'Usseau to the many modest worker's cottages (Longères) are still standing, having been built from large blocks of this beautiful material. Tuffeau is not only aesthetically pleasing, but its relative softness allows it to be easily cut, and dwellings made from this stone benefit from its characteristic as a natural insulator against extremes of hot and cold.