Polluce (Pollux), Champoluc, Ayas, Ayas Valley, Aosta Valley, Italy
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|Location is approximate, estimate based on other nearby localities.|
|Latitude & Longitude (WGS84):||45° North , 7° East (est.)|
|Margin of Error:||~10km|
|Other regions containing this locality:||The Alps, Europe|
|Köppen climate type:||Dfc : Subarctic climate|
|Name(s) in local language(s):||Polluce (Pollux), Champoluc, Ayas, Val d'Ayas, Valle d'Aosta (Vallée d'Aoste), Italia|
Polluce (4092 m a.s.l.), whose name in French and German is Pollux, is located on the border between Aosta Valley (Italy) and Valais (Switzerland). It is the lower of a pair of twin peaks, known as "I Gemelli" (Italian), "Die Zwillinge" (German) or "Les Jumeaux" (French), the other being Castore (Castor), named after the Gemini twins of Greco-Roman mithology. It is separated from Castor (4223 m) by Passo di Verra (Pas de Verra) or Zwillingsjoch (3845 m), to the southeast, and from Roccia Nera or Schwarzfluh (4075 m) by Porta Nera (Porte Noire) or Schwarztor (3725 m), to the northwest.
The Italian side of Polluce/Pollux is almost completely made of magnetite-bearing antigorite serpentinite (ophiolitic Zermatt-Saas nappe) with lenses and veins rich in reddish titanclinohumite, diopside, and olivine (forsterite). Serpentinite is in tectonic contact with amphibolite (Monte Rosa nappe), sometimes rich in epidote, at the base of the southeast crest and just above the terminal glacier crevasse on the south slope. A rodingite lens crops out on the orographic left of the steep couloir on the west slope; numerous rodingite bodies, varying in thinckness from decimetres to 4 metre, are present on the rocky south face, between its base and the top of the shoulder at 3991 m. Metarodingitic bodies are usually mantled by a thin chlorite rim and associated with garnet-bearing metagabbro, rich in epidote veins.
The presence in this area of crystals of red garnet, red-brown vesuvianite, green diopside, and prehnite was already reported by Hintze (1897). According to Güller (1947) and Dal Piaz (1967), garnet and diopside crystals in rodingite fissures and cavities are accompanied by clinochlore, vesuvianite, epidote, prehnite, and calcite. Grossular-rich garnet forms splendid crystals, ranging from pinkish to dark red; epidote appears as yellow to olive-green crystals up to 1 cm long, sometimes in association with white icositetrahedral crystals of analcime.
Minerals reported from the Swiss side are listed separately (see http://www.mindat.org/loc-121017.html).
14 valid minerals.
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Hintze, C. (1897) Handbuch der Mineralogie. Zweiter Band, Silicate und Titanate. Verlag von Veit & Comp., Leipzig, 1841 pp.
Güller, A. (1947) Zur Geologie der südlichen Mischabel- und der Monte Rosa-Gruppe. Eclogae Geologicae Helvetiae, 40, 39-161.
Dal Piaz, G.V. (1965) La formazione mesozoica dei calcescisti con pietre verdi fra la Valsesia e la Valtournanche ed i suoi rapporti strutturali con il ricoprimento Monte Rosa e con la zona Sesia-Lanzo. Bollettino della Società Geologica Italiana, 84, 1, 67-104.
Dal Piaz, G.V. (1966) Gneiss ghiandoni, marmi ed anfiboliti antiche del ricoprimento Monte Rosa nell'Alta Valle d'Ayas. Bollettino della Società Geologica Italiana, 85, 1, 103-132.
Dal Piaz, G.V. (1967) Le "granatiti" (rodingiti l.s.) nelle serpentine delle Alpi occidentali italiane. Memorie della Società Geologica Italiana, 6, 267-313.
Piccoli, G.C., Maletto, G., Bosio, P., Lombardo, B. (2007) Minerali del Piemonte e della Valle d'Aosta. Associazione Amici del Museo "F. Eusebio" di Alba, Ed., Alba, 607 pp.