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Dossi di Franscia (Franscia Mine; Franscia Mines; Franscia Quarries), Campo Franscia (Franscia), Lanzada, Lanterna Valley, Malenco Valley, Valtellina, Sondrio Province, Lombardy, Italy
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Name(s) in local language(s): Dossi di Franscia (Miniera di Franscia; Miniere di Franscia; Cave di Franscia), Campo Franscia (Franscia), Lanzada, Val Lanterna, Valmalenco (Val Malenco), Valtellina, Sondrio, Lombardia, Italia
 
At Dossi di Franscia, a group of hillocks to the SSW of Campo Franscia (Franscia) village, the various mineral sites can be grouped into: ancient asbestos mines and prospecting works, serpentinite quarries, and outcrops of mineralised veins and lenses in the country rock.
Minerals occur in different formation environments inside serpentinite: asbestos-andradite clefts, carbonate-rich fissures, titanian hydroxylclinohumite-forsterite-calcite veins, rodingite dykes, carbonate veins (hydrothermalites) with Ti-Ni-Cu minerals, and chromitite lenses and veins.

Asbestos-andradite clefts are the source of remarkable specimens of demantoid. For demantoid and fibrous chrysotile the best finds are recorded from the ancient mines, locally named “Trona Granda”, located in front of the building of Ristoro di Franscia and below the present Mauri serpentine quarry (now they are collapsed) (Sigismund, 1948; Gramaccioli, 1962 and other authors). Various other mines, quarries, prospecting works, and outcrops sporadically yielded good specimens of demantoid and fibrous chrysotile, such as: the serpentinite quarries (Mauri and Gerosa quarries) located, in proximity of the building of Ristoro di Franscia, below the spurs of Ciudé or Piodé (an elevation at the east foot of Motta Mt.); some old galleries in the little valley beneath the building of Ristoro di Franscia; the hillock overhanging the building of Ristoro di Franscia. Here, demantoid typically forms lenticular or spheroidal crystal nodules, attaining various centimetres in diameter, named “asbestos seed” (“semenza d’amianto”) by the miners/quarrymen.
Hydrated magnesium carbonates are sporadically found inside serpentinite fissures. Artinite was described as a new mineral species on specimens, consisting of white radiating veinlets, collected by Pietro Sigismund in 1902 at the old municipal asbestos mine, located after the chapel of Dossi di Franscia (Brugnatelli, 1902). A large fissure lined with artinite, as spherules of acicular crystals up to 2 cm in diameter, in association with hydromagnesite and probably coalingite was found in winter 1987-88 at Mauri serpentinite quarry. The first find of nesquehonite was recorded in 1921 from the “Trona Granda” asbestos mines (Artini, 1921).
Rodingite dykes crop out a few tens of meters from Ristoro di Franscia. Typical minerals are: colourless to white small crystals of diopside; colourless, pinkish or yellow rhombododecahedral crystals of grossular; green and yellow prismatic crystals of vesuvianite with red-brown terminations.
Magnetite, dolomite, pecoraite, and heazlewwodite in carbonate veins (hydrothermalites) have been found in the dump of an abandoned mine near Ristoro di Franscia (Bedognè et al., 1993). Finds of copper minerals (native copper, bornite, chalcocite, and cuprite) and other species (rutile, quartz, apatite, brucite, etc.) were reported by Sigismund (1947).
Chromitite lenses and veins at Dossi di Franscia are known for a long time. A chromitite lens was reported from the Ciatùn asbestos mine, whose location is no longer identifiable on the territory but probably in the area of the present Mauri serpentinite quarry. It was the source of bright emerald-green crystals of “uvarovite” (actually chromian andradite) in association with violet chromian clinochlore, asbestos, and probable sepiolite (Sigismund, 1948; Gramaccioli, 1962). Reevesite, zaratite, theophrastite, brucite, calcite, and prehnite have been found on the fractures of chromitite blocks from the dumps in the neighbourhood of Ristoro di Franscia. Chromitite lenses are also found at Mauri and Gerosa serpentinite quarries. A chromitite vein crops out in different places near Ristoro di Franscia.


NOTES
"Uvarovite": emerald-green crystals in chromitite fissures, traditionally considered "uvarovite" (Sigismund, 1948; Gramaccioli, 1962; De Michele, 1972, and other authors), are actually chromian andradite with a content in Cr2O3 varying inside the crystals from 9.6% in the core to 0.8% at the rim (Bedognè et al., 1993; Sciesa, 1993).

“Ti-bearing clinohumite, titanclinohumite”: according to the analyses performed, this mineral in the Malenco valley serpentinite is practically fluorine-free (Trommsdorff and Evans, 1980). Therefore, after institution of the new species hydroxylclinohumite in 1999, all records of “titanclinohumite” in the antecedent literature and specimens preserved in public and private collections consequently labelled are now Ti-bearing hydroxylclinohumite (Bedognè et al., 2006).

“Mauri quarry”: one of the serpentinite quarries at Dossi di Franscia is operated by the company Marmi Mauri S.r.l.. As the same company operates three serpentinite quarries in the municipal territory of Lanzada (at Le Prese, Valbrutta, and Dossi di Franscia respectively), some confusion can arise about the exact provenance of specimens simply labelled as from “Mauri quarry, Lanzada”. Nevertheless, the name Mauri quarry has been generally used among the mineral collectors to indicate the one of Le Prese (http://www.mindat.org/loc-233994.html), where vesuvianite-rich rodingite dykes have been evidenced.





Mineral List

Andradite
var: Demantoid
Antigorite
'Apatite'
Aragonite
Artinite (TL)
'Asbestos'
Bismuthinite
Bornite
Brucite
Calcite
Chalcocite
Chalcopyrite
'Chlorite Group'
Chromite
Chrysotile
Clinochlore
var: Chromian Clinochlore
Clinohumite
var: Titanclinohumite

Coalingite ?
Copper
Cuprite
Diopside
Dolomite
Epsomite ?
Forsterite
Grossular
Heazlewoodite
Hydromagnesite
Magnesite
Magnetite
Malachite
Morenosite
Nesquehonite
Pecoraite ?
Pectolite
Pentlandite
Perovskite
Prehnite
Pyrite
Quartz
Reevesite
Rutile
Sepiolite
Sphalerite
Talc
Theophrastite
Tremolite
Uvarovite
Vesuvianite
'Zaratite'


51 entries listed. 42 valid minerals. 1 type locality (valid mineral). 2 erroneous literature entries.

The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

Brugnatelli, L. (1902) Sopra un nuovo minerale delle cave d’amianto della Valle Lanterna. Rend. R. Ist. Lomb. Sc. Let., Serie II, 35, 869-874.

Artini, E. (1921) Sulla presenza della nesquehonite nelle cave d’amianto di Franscia in Val Lanterna. Rend. R. Acc. Naz. Lincei Cl. sc. fis. mat. nat., Serie 5, 30, 153-157.

Sigismund, P. (1947) Due interessanti paragenesi della magnetite in Valmalenco. Atti Soc. Ital. Sci. Nat., 86, 5-11.

Sigismund, P. (1948) Granato e vesuvianite in Val Malenco. Atti Soc. Ital. Sci. Nat., 87, 145-171.

Palache, C., Berman, H., Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892. John Wiley & Sons, New York. Volume II: 227.

Gramaccioli, C.M. (1962) I minerali valtellinesi nella raccolta di Pietro Sigismund. Ed. privata, Milano, 179 pp.

Bedognè, F. (1970) Località di ritrovamento dei demantoidi. In: Boscardin, M., De Michele, V., Scaini, G. Itinerari mineralogici della Lombardia. Ed. Museo Civ. St. Nat. e Soc. It. Sci. Nat., Milano, 77-80.

Amthauer, G., Kurtz, W., Rost, F., Schloemer, H. (1974) Chemismus und Genese des Andradits aus dem Serpentinit des Val Malenco (Bernina-Gebiet/Oberitalien). Schweiz. Miner. Petr. Mitt., 54, 691-706.

De Michele, V. (1974) Guida mineralogica d'Italia. Ed. De Agostini, Novara, 2 vol., 408 pp.

Gramaccioli, C.M. (1975) Minerali alpini e prealpini. Istituto Italiano Edizioni Atlas, Bergamo, 2 vol., 472 pp.

Bedognè, F. (1979) Itinerari mineralogici. Valmalenco e media Valtellina. Ed. Comunità Montana Valtellina-Ass. Turismo, Sondrio, 63 pp.

Bedognè, F. (1980) Die Mineralien der Grüngesteine des Val Malenco. Lapis, 1980/6, 9-13.

Trommsdorff, V., and Evans, B.W. (1980) Titanian hydroxyl-clinohumite formation and breakdown in antigorite rocks (Malenco - Italy). Contrib. Mineral. Petrol., 72, 229-242.

Bedognè, F., and Sciesa, E. (1993) Die Demantoide vom Val Malenco, Sondrio, Italien. Mineralien Welt, 1993/6, 25-28.

Bedognè, F., Montrasio, A., Sciesa, E. (1993) I minerali della provincia di Sondrio: Valmalenco. Bettini, Sondrio, 275 pp.

Sciesa, E. (1993) Le cromititi della Valmalenco (Alpi Centrali). Il Naturalista Valtellinese - Atti Mus. civ. Stor. nat. Morbegno, 4, 3-9.

Bedognè, F., and Sciesa, E. (1994) Asbestklüfte und ihre Mineralien im Serpentinit des Val Malenco (Sondrio, Italien). Mineralienfreund, 1994/4, 13-19.

Benetti, F. (1994) Guida mineralogica della Val Malenco. Grafica Mevio, Sondrio, 203 pp.

Bedognè, F., Sciesa, E., Vignola, P. (1999) Il “demantoide” della Valmalenco. Riv. Miner. It., 23, 4, 208-217.

Bedognè, F., Montrasio, A., Sciesa, E. (2006) I minerali della media-alta Valtellina, delle Orobie valtellinesi e della Val Poschiavo. Aggiornamenti sulle altre località della provincia di Sondrio. Bettini, Sondrio, 255 pp.

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