Candoglia marble quarries, Candoglia, Mergozzo, Verbano-Cusio-Ossola Province, Piedmont, Italyi

Regional Level Types
Candoglia marble quarries	Group of Quarries
Candoglia	Village
Mergozzo	Commune
Verbano-Cusio-Ossola Province	Province
Piedmont	Region
Italy	Country

Candoglia marble quarries, Candoglia, Ossola Valley, Verbano-Cusio-Ossola Province, Piedmont, Italy

Lenses of calcite and calc-silicate marbles, interlayered within the kinzigites of the Ivrea-Verbano Zone, with a subvertical attitude and small thickness (8-30 m). Structural studies evidenced isoclinal folds, with a subvertical axial plane parallel to the main foliation, which connect the different small lenses.

The quarries of Candoglia were first opened near the village, but later on, their location moved up to higher levels. Now there are five recognisable extraction sites:

- Madre quarry (Cava Madre), active underground quarry at an elevation of 560 m a.s.l.; This is the type locality for taramellite (Tacconi, 1908 a, b; 1911) and paracelsian (Tacconi, 1905; 1911).

- Carrettone quarry (Cava Carrettone), abandoned open pit quarry;

- Cornovo West quarry (Cava Cornovo Ovest), abandoned open pit quarry;

- Cornovo East quarry (Cava Cornovo Est), active open pit quarry at 860 m a.s.l.;

- Mergozzoni quarry (Cava Mergozzoni or Cava dei Mergozzoni), abandoned open pit quarry at 950 m a.s.l. This is the type locality for wenkite (Papageorgakis, 1959; 1961; 1962).

Historical note: since 24 October 1387 the Candoglia marble quarries belong to the "Veneranda Fabbrica del Duomo" of Milan. The Duke of Milan - Gian Galeazzo Visconti - gave the right to exploit for free the Candoglia marble and the woods located in the Grande Valley (Val Grande), in the area between Cima Corte Lorenzo and Alpe Ompio, as far as the course of Rio di Val Grande. The “Veneranda Fabbrica del Duomo” is still the concessionaire of this wooded territory, now included in the Val Grande National Park, whose confines are marked by boundary stones with the symbol of two crossed hammers. A large amount of timber was necessary for moving the marble blocks inside the quarries and from the quarries to the bank of the Toce River, where they were loaded onto wooden barges, 15-18 m long. The marble blocks sailed to Milan along the Toce River (navigable until the beginning of the 20th century), Lake Maggiore, the Ticino River, and the Naviglio Grande canal. Until 1439 the barges reached the Porta Ticinese dock (Darsena di Porta Ticinese) near the church of Sant’Eustorgio. Then, thanks to a new system of two locks to control the water level (known as Conca di Viarenna or Conca di Via Arena) designed by Ridolfo “Aristotele” Fioravanti and Filippino (Filippo) degli Organi, it was possible to connect the dock near Sant’Eustorgio to the inner canal system (Fossa Interna). It also allowed to transport the stones to Laghetto dell'Ospedale (a small basin filled in during 1857 and replaced by the modern-day Via Laghetto and Piazza Santo Stefano) near the Cathedral workshop. As the stones for the construction of the Cathedral were exempted from duties and tolls, the barges were marked with the letters “AUF” (Ad Usum Fabricae). This acronym originated the Milanese dialect expression “a uf” (sometimes used in the Italianised form “a ufo” or “a uffa”), which means “gratis, for free, free of charge”.

Today the produced stone (about 1,000 t/year) is only used for the restoration of the Cathedral (Ferrari da Passano, 2000). The Candoglia marble was also used in the past as facing stone in a few other monuments such as Certosa in Pavia, Cappella Colleoni in Bergamo, and San Petronio Cathedral in Bologna. Formerly, the Romans used it for columns and altars.

The medium- to coarse-grained Candoglia marble mainly shows a pink colour with frequent dark green layers, due to the presence of diopside and tremolite; other subordinate minerals are quartz, epidote, sulphides, Ba-feldspars, baryte, and rare phlogopite. The varieties of Candoglia marble (pink, white, grey, and veined) are deeply affected by the chromatic, textural, and compositional features.

Note on the mineral list: The Ba silicate found at the contact between calciphyres and amphibolite and described as "calciocelsian" by Peyronel Pagliani (1958) is ascribable to armenite. The presence of armenite, in the form of prismatic crystals, has been recently confirmed (Gentile et al., 2017).

Other Regions, Features and Areas containing this locality

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