Tuffeau stone — in French, simply ''tuffeau'' or ''tufeau'' — is a local

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

of the Loire Valley of

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...

. It is characterized as a chalky or sandy, fine-grained limestone, white to yellowish-cream in appearance, and micaceous (containing some white flakes of mica, or

muscovite Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated phyllosilicate mineral of aluminium and potassium with formula K Al2(Al Si3 O10)( F,O H)2, or ( KF)2( Al2O3)3( SiO2)6( H2O). It has a highly perfect basal cleavag ...

). 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.

Geology

Tuffeau dates to the Mesozoic era ( Upper Cretaceous Turonian stage). 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. It differs from genuine

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Ch ...

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 A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...

, the coccolith, which was deposited in deeper (~ 200 meters), and quieter, water. The term ''tuffeau'' is etymologically related to another stone,

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock ...

, to which is it not geologically related — and to

tufa Tufa is a variety of limestone formed when carbonate minerals precipitate out of water in unheated rivers or lakes. Geothermally heated hot springs sometimes produce similar (but less porous) carbonate deposits, which are known as travertin ...

, to which it is geologically related. These words derive from Italian ''tufo'' and from Latin ''tōphus'' or ''tōfus'' ("stone").

Physical properties

Tuffeau has a very low density compared with many other rocks, being half as dense as granite, comparable in density with ebony, and only about 10 to 20% heavier than water. It has porosity of up to 50%, whereas that of granite is only about 1%. The compressive strength of the stone is a factor of 10 to 20 times less than that of granite. When mixed with local sand and flinty clays from later eras, tuffeau is said to create the best vineyards soils.

Mining

Carrière de tuffeau à Bourré, Loir-et-Cher

Tuffeau mining reached its peak in the

15th century The 15th century was the century which spans the Julian dates from 1 January 1401 ( MCDI) to 31 December 1500 ( MD). In Europe, the 15th century includes parts of the Late Middle Ages, the Early Renaissance, and the early modern period. ...

. As a construction material — especially in the

Touraine Touraine (; ) is one of the traditional provinces of France. Its capital was Tours. During the political reorganization of French territory in 1790, Touraine was divided between the departments of Indre-et-Loire, :Loir-et-Cher, Indre and Vien ...

and Anjou regions — tuffeau has been extracted mostly from natural riverside bluffs, which are extensive. The extracted blocks could thus be loaded onto boats. Over the centuries, this has created extensive underground galleries, or mines, some of which are several kilometers in extent. These artificial caves have long been used as human dwellings, as the indoor temperature is remarkably constant from summer to winter. The greatest concentration of these cave dwellers — ''les troglodytes'' — is in the region of Saumur. Montrésor tuffeau

The mines are a perfect environment for wine cellars. Many of the larger caves have become '' champignonnieres'' — i.e., are used for growing a commercial variety of mushroom, which is transported daily to the markets of Paris.

Architecture

Numerous buildings in the Loire Valley, from the most modest to the most grandiose, were built from blocks of tuffeau stone, including the Château de Beaulieu near Saumur, the Château d'Ussé and the Château de la Motte d'Usseau, and many worker's cottages at Longères.

Geology

Physical properties

Mining

Architecture

See also