BROSSO mine

 

This mine is relatively close to Milan and is a very famous locality. One of the few where it is still now possible to make some interesting finding. It is very often visited by ourselves and the other mineral collectors of northern Italy. During the last years we made a serie of discoveries from which we propose a selection of very interesting and representative specimens, in some cases ( like Ludwigite, Canavesite and Pharmacolite ) in some of the best cristallisations worldwide. Consider that the name "canavesite" derives from "canavese", the region in which the Brosso mine is located.  Since most of this specimens are from our findings we are open also to trades.

In this page you can find a description and some curiosities about the locality.

 

Geographical setting

The old mines of Brosso are relatively close to Brosso city, but are in the area of Lessolo from which are easily reachable. From Ivrea you have to reach Lessolo and from this Calea.panorama1.jpg (13331 byte) .There are different indications to the Mine and also to the  restaurant close to the mine and called " La miniera" ( very good food at reasonible prices). All the different levels of the mine are along or close to the Assa river. Now the material external to the mine is very old and very exploited from the mineralogical point of view, so almost all the minerals can be found only in the galleries.     

 

 

 

Geology

From the geological point of view the mine is located on a classic thermo-methamorphic contact area due to the intrusion of a granodiorite batholit ( a granitoid rock ).  The batholit is called " Diorite di Traversella " and is very small( geologically speaking )  but with a large metamorphic area with several metallic mineralisations. These were  exploited in the Brosso mines and in the more famous TraversellBepi7.jpg (14196 byte)a mines not anymore visitable now. As well known, normally the intrusion of igneous rocks has the effect of metamorphizing the surrounding rocks,  in this case methamorphic schists with calcareous layers .   With the igneous intrusion and partially due also to the methamorphic processes there are some fluids circulating . These fluids are extremely rich of diluted minerals and they cristallize raising in the rocks and reaching lower pressures and temperatures.  In the case of Brosso, the mineralisation is mainly related to the calcareous masses, mineralised at metallic oxides and sulphurs . The main ore minerals are magnetite, Hematite and Pirite, but in paragenesis with a lot of different other minerals ( more than 80 species have been officially found )

History

The mines are very old and known since the roman period.  Then until the 18th century the mines were exploited for the iron. The ore minerals were hematite and magnetite.

From the beginning of the 19th century the exploited mineral became the pirite, used before to get the "vetriolo di ferro", very important for the textile industry and then ( from 1858 ) for the solphoric acid.   It is very complex to reach the mineralogical locality and from the athletical point of view is very hard..... at least in our idea.....' .

 

The mine and the research campaign

The mine is really enormous. It has been exploited since the roman time and there is a citation of the famous roman writer Plinio of this mine. 

As a consequence there is a lot of different galleries and different levels of exploitation. The sistem and the kine is characterised by relatively barren galleries and by huge caves derived by the excavation of the minerals. Some of these caves are 400-500 m long by 100-200 m large and 10-15 m high. To preserve from possible shakeout, some columns have been left by the miners and the atmosphere and the aspect of these caves is relly particular and interesting.  Finally the water isbros1.jpg (30170 byte) inside a lot of the different levels creating small creeks, and small lakes inside. Our opinion is that this mine is one of the most "beautiful" of the region and a visit is worth for its particularity.

The levels we have explored are:

  SALVERE level. It is The lowest level, very close to the road where you can park the car. The level is very wide with a lot of galleries. In this level you can find the very rare Ludwigite that is located in a unique place but well detectable due to the large quantity of detrites and to the traces of work of the rock hounders. Pay attention : the mineral is extremely hard and is really difficult to collect nice and representative samples. Related with the Ludwigite there is the rare Canavesite in white acicular small XX. Other minerals of this level are Magnetite, in black bright XX, hematite and scheelite, in green to yellow XX, very rare. Calcite and dolomite are also very common. In some lower galleries now not anymore visitable due to the water and shakeout there was also the prasio quartz in very nice green XX .

bros2.jpg (23357 byte)GIERINIERE level. This is an area where we made a lot of research. The level is famous for the barite  cristals that have been found. Also in recent times ( 1993 ) a geode of more than 7 meters of lenght has been found with white or trasparent barite XX of more than 30 cm!! The most aesthetic association of the barite crystals is with the siderite. The Barite, in white, pink, light blue or trasparent crystals on a carpet of centimetric deep brown to black siderite crystals has a really aethetic effect and is very nice. In some samples very nice balls of white pharmacolite complete an uncommon and interesting paragenesis. In the level it is possible to find also calcite ( dog teeth) pirite, marcasite, magnetite and hematite.

S.GIUSEPPE level: it is the highest level we explored, it is at about 45 minutes of walk from the car park, following the small road starting from the car parking. This level is famous for the pirite crystals of more than 10 cm that has been found ia association with quartz. In the level you can find now the rare boulangerite, bournonite . We have found a zone with centimetric very trasparent gypsum cristals in association with pyrite, siderite, calcite and dolomite. The geodes are very nice and the occurrence of gypsum, related to the oxidation of the pirite, is particular of the locality. Other minerals are Quartz, in white to green cristals, ....... bros3.jpg (16032 byte)

A general recommandation for whoever has the intention to visit the mine is important.

1- The mine  is  very old and the state of  the galleries is dangerous. Explore the galleries with a lot of prudence and never alone.

2- All the litter should be taken with yoursel, without leaving anythig in this zone, very nice and interesting also from the natural point of view.

 

Minerals

As previously stated, a lot of different species has been found in the mine. Here below alist with the frequency of occurrence:

Native elements

Sulphur (rare)  Arsenicum (r)

Sulphurs

Sphalerite ( rare )  Bornite ( rare ) Calchopirite ( rare ) Pirrotine ( r ) Galena ( not common ) Bismutinit ( r ) Pirite ( very common ) Marcasite ( common )

Solfosali

Bournonite ( r) Tetraedrite ( r) Boulangerite (r) Jamesonite (r)

Alogenuri

Fluorite ( r )

Oxides

Arsenolite (r) Magnetite ( common ) Hematite ( c) Quartz ( c) Rutile ( r ) Anatase ( r) Brookite (r) Plattnerite ( r) Uraninite ( r) Melanophlogite (r)

Idroxides

Goethite (c) Limonite (vc) Brucite ( r)

Carbonates

Siderite ( vc) Mesitine ( c) Calcite ( c) Dolomite (vc) Aragonite ( vc) Smithsonite ( pc) Cerussite (r) Ankerite (nc ) Bismutite (r) Auricalcite ( r) Nesquehonite (r) Idromagnesite (r) Piroaurite (r) Dypingite (r) Canavesite ( r)

Borates

Kotoite (r) Szaibelite (r) Inderite (r) Ludwigite (nc)

Sulphates

Barite (nc) Gypsum (nc) Anhidrite (r) Melanterite (r) Pickeringite (r) Svanbergite (r)

Wolphramates

Wolphramite (r) Ferberite (r) Scheelite (r) Cuprotungstite (r)

Phosphates

Apatite (r) Pyromorphite (r)

Arseniates

Picropharmacolite (r) Pharmacolite (r)

Silicates

Grossularia ( nc) Phorsterite (r) Andradite (r) titanite (r) Chloritoide (r) Epidote (r) Diopside (r) Phassaite (r) Hyperstene (r) Actinolite (r) Horneblende (r) Glaucophane (r) Pirophillite (r) Biortite (c) Clinoclore (r) Antigorite (r) Lizardite (r) Crisotile (r) Cronstedtite (r) Sepiolite (r) Allophane (r) Talc (c) Orthoclase (r)

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