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Prabornaz Mine (ex Praborna Mine), Saint-Marcel, Aosta Valley, Italy

Photo: machv83
Latitude: 45°40'46"N
Longitude: 7°26'58"E
Miniera di Prabornaz, Saint-Marcel, Valle d'Aosta, Italia

The manganese concentrations of Prabornaz are restricted to a 4x8 m thick quartzite unit of diverse lithologies which represent the basal part of the sedimentary cover of an ophiolite suite. Together they constituted the Piedmont Nappe which was metamorphosed up to the eclogite facies in Cretaceous times and was retrogressed in the early Tertiary.

The quartzite unit is composed of a succession of siliceous levels characterized by Mn-bearing minerals reflecting differences in chemical composition and oxygen fugacity inherited from the original sediments. The parageneses evolved during the polyphasic Alpine metamorphism passing through a pre-eclogite blue-schist facies event, the main eclogite facies event, and the several post-eclogite stages terminating in the greenschist facies.

These Mn concentrations were subsequently penetrated by several networks of cross-cutting veins and late fractures which were responsible for the mobilization of certain elements, in particular K, Sr and Ba.


Mineral List

Actinolite
Aegirine
Aegirine-augite
Albite
Aluminoceladonite
Anatase
'Ardennite'
Birnessite
Braunite (TL)
Calcite
Calderite
Celadonite
'Chlorite Group'
Clinochlore
Clinozoisite
Cryptomelane
Diopside
Diopside
var: Schefferite

var: Violane
Edenite
Epidote
Ferri-ghoseite
Fluorapatite
Gold
Hausmannite
Hematite
Hollandite
Ilmenite
Jacobsite
Jadeite
Kutnohorite
Magnesiochloritoid
Magnetite
Manganiandrosite-(Ce) (TL)
Manganite
Microcline
Muscovite
var: Alurgite
Neotocite
Omphacite
Pentlandite
'Phengite'
Phlogopite
Piemontite (TL)
Piemontite-(Sr)
Priderite
Pyrolusite
Pyrophanite
Pyroxmangite
Quartz
Rhodochrosite
Rhodonite
Richterite
'Roméite Group' (TL)
Rutile
Spessartine
Strontiomelane (TL)
Talc
Tephroite
Tiragalloite
Titanite
var: Greenovite
Todorokite
Tremolite
Uvarovite
Violarite
Winchite


67 entries listed. 59 valid minerals. 4 type localities (valid minerals). 1 type locality (other).

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References

- Rondolino R. (1934) Sopra alcuni minerali di S. Marcel (Valle d'Aosta). Periodico di Mineralogia – Roma 123-139.
- Rondolino R. (1936) Sopra alcuni anfiboli manganesiferi di Praborna (San Marcel, Valle d'Aosta). Periodico di Mineralogia – Roma pp. 109-121.
- Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 1021.
- Bondi, M., Mottana, A., Kurat, G. & Rossi, G. (1978): Cristallochimica del violano e della schefferite di St. Marcel (Valle d'Aosta). Rendiconti della Società Italiana di Mineralogia e Petrologia, 34, 15-25.
- Brown, P., Essene, E. J. & Peacor, D. R. (1978): The mineralogy and petrology of manganese-rich rocks from St. Marcel, Piedmont, Italy. Contrib. Mineral. Petrol. 67, 227-232.
- Mottana, A., Rossi, G., Kracher, A., & Kurat, G. (1979). Violan revised: Mn bearing Omphacite and Diopside. Tschermaks Min. Petr. Mitt., 26, 187-210.
- Martin, S. (1983): La mine de Praborna, Val d'Aoste (Italie): une série manganesifère metamorphoisée das la facies éclogite. These 3me cycle, Univ. Paris VI, xx pp.
- Martin-Vernizzi, S. (1984) La mine de Praborna (Val d'Aoste, Italie: une série manganésifère métamorphisée dans le faciès éclogite. Thèse de doctorat, Université Pierre et Marie Curie, Paris, France.
- Perseil, E. A. (1985): Some characteristics of manganese oxide facies in the deposit at St. Marcel-Praborna-Val d'Aosta, Italy. Miner. Deposita 20, 271-276. (in French)
- Preite, D. (1985): La pagina dei Micromounts – Omfacite di Quincinetto e Praborna. Rivista Mineralogica Italiana, 9(2), 88.
- Perseil E. A. & Smith D. C. (1995) Sb-rich titanite in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrography and crystal chemistry. Mineralogical Magazine: 59: 717-734.
- Smith, D.C. and Perseil, E.-A. (1997) Sb-rich rutile in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrology and crystal-chemistry. Mineralogical Magazine: 61: 655-669.
- Perseil, E. A. (1998) Evolution cristallochimique des oxydes de manganèse dans le gisement de St. Marcel Praborna (V. Aoste, Italie) - Rend. Fis. Acc. Lincei, s. 9, v. 9 (1998) 4, pp. 315 - 336
- Piccoli, G.C., Maletto, G., Bosio, P., Lombardo, B. (2007): Minerali del Piemonte e della Valle d'Aosta. Associazione Amici del Museo "F. Eusebio" Alba, Ed., Alba (Cuneo) 607 pp.
- Tumiati, S., Martin, S., Godard, G. (2010): Hydrothermal origin of manganese in the high-pressure ophiolite metasediments of Praborna ore deposit (Aosta Valley, Western Alps). European Journal of Mineralogy 22, 577-594.

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