Ornavasso marble quarries, Ornavasso, Verbano-Cusio-Ossola Province, Piedmont, Italyi

Regional Level Types
Ornavasso marble quarries	Group of Quarries
Ornavasso	Commune
Verbano-Cusio-Ossola Province	Province
Piedmont	Region
Italy	- not defined -

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

Lenses of calcite and calc-silicate marbles, interlayered within the kinzigites of the Ivrea-Verbano Zone.

The Ornavasso marble quarries are located on the right side of Ossola Valley, in front of the famous Candoglia marble quarries [see: http://www.mindat.org/loc-2101.html]. The Ornavasso marble is similar to the Candoglia one, but it less valuable than the latter, due to the coarse grain size, dark colour or more abundant dark veins. Marble at Ornavasso has been intermittently exploited from five extraction sites: two underground and three open pit quarries. The most known quarry (Casino Visconti quarry) is located in a hair-pin bend along the road from Ornavasso to the Sanctuary of Madonna del Boden, in the historical area of Casino Visconti.

Already exploited in ancient times, the Ornavasso marble gained importance at the end of the 14th century because it was used as building stone (together with the more valuable Candoglia marble) in the Milan Cathedral (Duomo). It was also used in other famous monuments, such as the Cathedral of Pavia, the church of Madonna di Campagna in Verbania-Pallanza, the apsides of the churches of San Carlo and Santa Cristina in Turin, Arco della Pace in Milan, etc.

There are four main marble varieties: pink (commercially known as Rosa Valtoce marble, with abundant dark veins), grey (commercially known as Grigio Boden marble, showing a dark homogeneous colour), white (known in the past as Chiaro Butino marble), and veined. The pink variety is a medium- to coarse-grained calcite marble which shows a pink colour with frequent dark green layers, due to the presence of diopside and tremolite; other subordinate minerals are quartz, epidote, phlogopite, Ba-feldspars, baryte, and iron sulphides. In the grey and veined varieties calcium silicates are homogeneously distributed. The so-called "Granitello del Boden" variety is a foliated calcite marble with subordinate quartz nodules and silicates (tremolite, diopside, muscovite) and traces of sulphides, titanite, and baryte.

Crystals of pyrite from the Ornavasso marble were studied by Boeris (1890).

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References