Desertetto Valley quarries (Cima Cialancia quarries), San Lorenzo, Valdieri, Cuneo Province, Piedmont, Italyi

Regional Level Types
Desertetto Valley quarries (Cima Cialancia quarries)	Group of Quarries
San Lorenzo	Village
Valdieri	Commune
Cuneo Province	Province
Piedmont	Region
Italy	Country

Inactive marble quarries, opened in a large mass of recrystallised rocks of the Dauphinois sedimentary succession (Aptian-Cenomanian Marne Nere unit, and Upper Cretaceous Puriac Limestone), in the upper Desertetto Valley along the south slope of Cima Cialancia-Cresta dell'Arp. The marble, particularly the variety commercially known as "Cipollino Dorato di Valdieri", was seasonally extracted from the 1920s to the 1970s by using helicoidal wire saws. It was used for various public buildings in Italy (Politecnico and the new Teatro Regio in Turin) and abroad (County Hall in London, Georgi Rakovski Military Academy in Sofia, Sidi Hamuda mosque in Tripoli, Círculo Italiano in Buenos Aires, National Capitol Building in Havana, Grand Palace in Bangkok).

In the Cima Cialancia-Cresta dell'Arp sector, the dark calcareous schist deriving from the recrystallisation of the Marne Nere unit (dark-coloured shales and marls) are covered by 20-30 meters of white and grey marbles, commonly banded, with rare phyllosilicate levels, followed by 15-20 meters of white marbles with millimeter-sized dolostone clasts. The succession continues with silicate-bearing marbles, representing the peculiar lithotype known as "Cipollino di Valdieri", which was exploited in the quarries.
From a macroscopic point of view, this is a white or ivory-colored marble, with millimeter-thick, anastomosed phyllosilicate levels, with a dark-green or purple colour. Locally, the rock is crossed by a dense framework of thin orange veins, composed of Fe-carbonate. In thin section, the rock is composed of heterometric calcite crystals, commonly exhibiting polysynthetic twinning, ranging in size between 100 and 300 μm, even if locally levels with smaller crystal size (20-100 μm) are present. Calcite levels are alternated with subparallel levels mainly composed of white mica (muscovite-paragonite solid solutions spanning a wide composition range, from almost pure muscovite Mu₉₁ to paragonite-rich terms Pg₈₅) and chlorite. Epidote, in subhedral crystals 100-500 μm long, and hematite are common accessory phases in phyllosilicate levels and are locally very abundant. Rare titanite and tourmaline crystals are also present. Locally, abundant detrital grains are present, represented by mono- or poly-crystalline quartz with undulose extinction or clasts of volcanic rocks. These detrital grains are mostly contained in the phyllosilicate-rich levels, less frequently they can be observed as isolated grains within the calcite levels. In the quarries, the "Cipollino di Valdieri" marbles contain conglomerate levels with centimeter-sized carbonate clasts, and breccia bodies. Breccias are composed of angular or subangular marble clasts (centimeter-sized to decimeter-sized) surrounded by a phyllosilicate-rich matrix. Recrystallised rocks of the Desertetto Valley are commonly crossed by veins, some millimeter to a few decimeters thick. They are mainly composed of calcite, in centimeter-sized crystals commonly associated with subhedral quartz crystals. Veins crossing the "Cipollino di Valdieri" marbles contain also green epidote and hematite.

Fossils

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References