The Dora-Maira Unit (Italian Cottian Alps): a reservoir of ornamental stones locally and worldwide employed since Roman age

The Dora-Maira Unit is a geological unit cropping out in the inner part of the Cottian Alps and belonging to the Penninic Domain of the Western Alps (northwestern Italy). It consists of a Paleozoic basement and its Mesozoic carbonate cover, metamorphosed under eclogite facies conditions in the Cenozoic. Due to the complexity of the rock associations and the textural-metamorphic transformations, the Dora-Maira Unit has been a source of ornamental stones over the centuries, and still represents a reservoir of material locally employed for historical and contemporary buildings. Several varieties of orthogneiss, quartzite and marble, derived from the Paleozoic basement and Mesozoic cover, are known by different local names (e.g. Luserna Stone, Borgone and Vaie Stone, Perosa Stone, Bargiolina Quartzite, Foresto and Chianocco Marble).These stones were largely employed during the 17th and 18th centuries for some of the most famous and important monuments in Turin (capital of Piedmont region, northwestern Italy), as well as in the countryside, since Roman times. Some of the materials exploited in the Dora-Maira Unit were also exported to foreign countries: Borgone and Vaie Stone were used for the paving of the Louvre Museum, and Perosa Stone was employed for the construction of the monument of Independence in Lagos, Nigeria. Consequently, the Dora-Maira Unit can be designated as a Global Heritage Stone Province.