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Jahnsite-(MnMnFe), Mn (super 2+) Mn (super 2+) Fe (super 2+) 2Fe (super 3+) (sub 2) (PO (sub 4) )4(OH) (sub 2) .H (sub 2) O, a new phosphate mineral from the Malpensata Pegmatite, Olgiasca, Volico Municipality, Lecco Province, Italy

Pietro Vignola, Frederic Hatert, Nicola Rotiroti, Fabrizio Nestola, Andrea Risplendente and Francesco Vanini
Jahnsite-(MnMnFe), Mn (super 2+) Mn (super 2+) Fe (super 2+) 2Fe (super 3+) (sub 2) (PO (sub 4) )4(OH) (sub 2) .H (sub 2) O, a new phosphate mineral from the Malpensata Pegmatite, Olgiasca, Volico Municipality, Lecco Province, Italy
The Canadian Mineralogist (March 2019) 57 (2): 225-233

Abstract

Jahnsite-(MnMnFe), Mn (super 2+) Mn (super 2+) Fe (super 2+) (sub 2) Fe (super 3+) (sub 2) (PO (sub 4) ) (sub 4) (OH) (sub 2) .8H2O (IMA 2018-096), is a new phosphate belonging to the jahnsite subgroup of the jahnsite group of minerals. It was found in the dumps of the Malpensata pegmatite mine close to the village of Olgiasca, Colico municipality, Lecco province, Italy by one of the authors (F.V.). The mineral occurs on the surfaces of a hydrothermal cavity as prisms elongated along a, weakly flattened on {010}, and twinned by reflection on {001}, up to 130 mu m in size. The new species occurs in close association with rockbridgeite as a late stage product of alteration of primary phosphate minerals including graftonite-(Mn). Its color is dark brown and it is partially transparent with a vitreous luster. The streak is pale greenish brown. Jahnsite-(MnMnFe) is brittle with a good cleavage on {001}. Its Mohs hardness is 4 and the calculated density is 2.654 g/cm (super 3) . The mineral is optically biaxial (-) with alpha = 1.673, beta = 1.685, gamma = 1.689, and 2V (calc.) = 60 degrees , and it is non-fluorescent under 254 nm (short wave) and 366 nm (long wave). The empirical formula is: (Mn (sub 0.40) Ca (sub 0.25) Na (sub 0.05) ) (sub Sigma 0.70) Mn(Fe (super 2+) (sub 1.39) Mn (sub 0.43) Mg (sub 0.14) Zn (sub 0.0 3) ) (sub Sigma 2. 00) (Fe (super 3+) (sub 1.99) Al (sub 0.01) ) (sub Sigma 2) (PO (sub 4) ) (sub 4) (OH) (sub 1.35) .8H (sub 2) O. Jahnsite-(MnMnFe) is monoclinic, with space group P2/a and unit-cell parameters a = 15.1559(6) Aa, b = 7.1478(2) Aa, c = 10.0209(4) Aa, and beta = 112.059(4) degrees with V = 1006.11(6) Aa (super 3) for Z = 2. The eight strongest measured lines in the XRPD pattern are [d in Aa, (I/I0), (hkl)]: 2.590 (100) , 9.221 (89) (001), 2.840 (82) (320), 4.932 (78) , 4.651 (78) (002), 3.971 (71) (211), 3.504 (64) , and 3.295 (46) . Its crystal structure was refined and conforms with the general structure described for jahnsite-group minerals.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 57
Serial Issue: 2
Title: Jahnsite-(MnMnFe), Mn (super 2+) Mn (super 2+) Fe (super 2+) 2Fe (super 3+) (sub 2) (PO (sub 4) )4(OH) (sub 2) .H (sub 2) O, a new phosphate mineral from the Malpensata Pegmatite, Olgiasca, Volico Municipality, Lecco Province, Italy
Affiliation: CNR, Istituto per la Dinamica dei Processi Ambientali, Milan, Italy
Pages: 225-233
Published: 201903
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 22
Accession Number: 2019-029445
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N46°06'00" - N46°10'00", E09°19'60" - E09°24'00"
Secondary Affiliation: Universite de Liege, BEL, BelgiumUniversita degli Studi di Milano, ITA, ItalyUniversita degli Studi di Padova, ITA, Italy
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201916
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