...Elena-Adriana Perseil; Philippe Blanc; Daniel Ohnenstetter Abstract We describe important variations in the crystal chemistry of fluorapatite from the manganiferous deposit at the St. Marcel – Praborna mine in the Val d’Aosta, Italy. Three types of fluorapatite were observed...

...David C. Smith; Elena-Adriana Perseil Abstract The petrographical, crystal-chemical and petrogenetical aspects of rutile rich in antimony (up to 33.75 wt.% Sb 2 O 5 ; equal to 0.2 Sb (super +) per O = 2) from St. Marcel-Praborna in the Aosta Valley, Italy, were re-examined. These compositions occur...

...+ in the M1 site; it occurs at the Praborna manganese mine, Saint-Marcel, Aosta valley, Italy, in a Mesozoic eclogite-facies ophiolitic unit of the western Alps. Associated minerals are rhodochrosite and Mn-pyroxenoid, with minor calderite, spessartine, hematite and pyrophanite. The structural formula is A1...

... ). However, a discussion arose on the origin and evolution of the few Mn ores associated with meta-ophiolites and strongly metamorphosed at high-pressure conditions, such as those of Praborna (Italy; this study) and Andros (Greece; e.g ., Reinecke, 1985 ). Their actual origin, hydrogenous ( i.e...

... Ti 4+ , where M 5+ can be V 5+ , Ta 5+ Nb 5+ , Sb 5+ and M 2+ is Fe 2+ or Mn 2+ ; M 3+ + M 5+ ↔ 2Ti 4+ , where M 3+ is Fe 3+ , Mn 3+ , Al). In rutile from St. Marcel-Praborna, Italy, Smith & Perseil (1997) recognised that Sb is present entirely as Sb 5+ , and substitutes...

... ) and Perseil et al. ( 2000 ). In particular, Perseil et al. ( 2000 ) described As-bearing fluorapatites in the manganiferous deposit of St Marcel-Praborna (Italy) and related their formation to the late circulation of fluids enriched in As and Sr. The cathodoluminescence technique enables progressive...

... a chemical and crystallographic characterization of the mineral, we present a detailed petrological study and thermodynamic modeling, to deduce the formation conditions of this mineral. The Praborna manganese ore (Saint-Marcel valley, Italy; Fig. 1 ), hosted in metaophiolites belonging to the Zermatt...

... described with a double b (or c , according to a tetragonal cell) periodicity, i.e . ferrihollandite from Kajlidongri, India ( Mukherjee, 1960 ) and strontiomelane from Praborna, Italy ( Meisser et al. , 1999 ). In the priderite group, Szymański (1986) solved the 5.8 Å structure of mannardite...

... of manganese oxides: guides to metallogenesis . Econ. Geol . 87 , 1253 – 1264 . 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 . Mineral. Mag . 59 , 717...

... (Praborna mine, St. Marcel Valley, Piemonte, Italy) piemontite occurs in the upper parts of a Mn ore deposit composed of micaschist that include bands of Mn silicates (spessartine, piemontite, Mn phengite) with lenses of Mn oxides intercalated with bands rich in Fe silicates (epidote, clinopyroxene...

... of the cryptomelane group from St. Marcel–Praborna, Aosta Valley, Italy. Can. Mineral., 37, 673–678. The most Sr-rich of six listed electron microprobe analyses has MnO 2 58.71, Mn 2 O 3 16.51, Fe 2 O 3 6.27, TiO 2 0.70, SiO 2 0.45, K 2 O 0.83, Na 2 O 0.17, BaO 1.39, SrO 12.77, sum 97.80 wt%, corresponding...

..., space group I 4/ m . Strontiomelane has been described as a strontium analogue of cryptomelane ( Meisser et al. , 1999 ). Its ideal chemical formula is Sr(Mn 4+ 6 Mn 3+ 2 )O 16 . The type locality is the Praborna mine, St. Marcel, Aosta Valley, Italy. No structural information is available...

... have been reported from Mn deposits ( Perseil 1988 ; Cabella et al. 1995 ) and a piemontite quartzose schist (metachert) ( Banno 1996 ). Strontiomelane, a Sr-analogue of hollandite, was recently reported from the Praborna Mn deposit, Italy ( Meisser et al. 1999 ). This occurrence shows...

... have been described from carbonate pods in Mn-rich metacherts. Manganiandrosite-(Ce) was discovered in the Praborna Mn deposit, Saint-Marcel, Val d’Aosta, Italy, which belongs to the eclogitic facies ophiolitic Zermatt-Sasas Unit within the Western Alps. The deposits occur as quartz-rich lenses...

... of central Italy . Tectonophysics , 223 , 117 – 147 . Smith 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 . Taylor S.R...

..., omphacite-jadeite-aegirine, pyroxmangite, piedmontite, phengite, glaucophene, hematite, ardennite P = 2.0–2.6 GPa T = 450–550 °C This study Praborna Mn-ore deposit, Zermatt-Saas, Western Alps Fe-Mn Chert in meta-ophiolites, eclogite, blueschist Garnet, omphacite-jadeite-aegirine, pyroxmangite...

... of the LREE and Th during alteration— H.-J. Förster 67 As-bearing fluorapatite in manganiferous deposits from St. Marcel–Praborna, Val d’Aosta, Italy— E.-A. Perseil, P. Blanc, and D. Ohnenstetter 101 Complexly zoned fibrous tourmaline, Cruzeiro mine, Minas Gerais, Brazil: A record of evolving...