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GEOREF RECORD

The walentaite group and the description of a new member, alcantarillaite, from the Alcantarilla Mine, Belalcazar, Cordoba, Andalusia, Spain

Ian E. Grey, Rupert Hochleitner, Christian Rewitzer, Alan Riboldi-Tunnicliffe, Anthony R. Kampf, Colin M. MacRae, W. Gus Mumme, Melanie Kaliwoda, Henrik Friis and Carlos U. Martin
The walentaite group and the description of a new member, alcantarillaite, from the Alcantarilla Mine, Belalcazar, Cordoba, Andalusia, Spain
Mineralogical Magazine (June 2020) 84 (3): 412-419

Abstract

The general structural formula for the walentaite group is [((A1yA1' (sub 1-y) ),A2) (H (sub 2) O) (sub n) ][Bx(As2) (sub 2-x) (As3)M1(M2) (sub 2) (TO (sub 4) ) (sub 2) (O,OH) (sub 7) ], based on heteropolyhedral layers of configuration [M1(M (sub 2) ) (sub 2) (TO (sub 4) ) (sub 2) (O,OH) (sub 6) ], with surface-coordinated species at the B, As2 and As3 sites, and with interlayer hydrated cation groups centred at the A sites. The group is divided into walentaite and halilsarpite subgroups based on T=P (super 5+) and As (super 5+) , respectively. Alcantarillaite, (IMA2019-072), [Fe (super 3+) (sub 0.5[]0.5) (H (sub 2) O) (sub 4) ] [CaAs (super 3+) (sub 2) (Fe (super 3+) (sub 2.5) W (super 6+) (sub 0.5) )(AsO (sub 4) ) (sub 2) O (sub 7) ], is a new member of the walentaite group from the Alcantarilla wolframite mine, Belalcazar, Cordoba, Andalusia, Spain. It occurs most commonly as lemon-yellow fillings together with massive scorodite in fissures and cracks in quartz adjacent to lollingite. It is also found as tiny yellow rosettes lining vugs and as spheroids of ultrathin blades. It is associated with scorodite, pharmacosiderite, ferberite and schneiderhohnite. Optically it is biaxial (-), with alpha =1.703(calc), beta =1.800(5), gamma =1.850(5) and 2V=68(1) degrees (white light). Dispersion is r>v, moderate. The optical orientation is X=a, Y=c and Z=b. The calculated density is 3.06 g cm (super -3) . Electron microprobe analyses together with crystal structure refinement results gives the empirical formula [Fe (super 3+) (sub 0.52[]0.48) (H (sub 2) O) (sub 4) ] [(Ca (sub 0.44) K (sub 0.11) Na (sub 0.05) Fe (super 2+) (sub 0.24[]0.42) )As (super 3+) (sub 1.83) ] [Fe (super 3+) (sub 2.54) Al (sub 0.03) W (super 6+) (sub 0.43) )((As (sub 0.65) P (sub 0.35) )O (sub 4) ) (sub 2) O (sub 5.86) (OH) (sub 1.14) ]. Alcantarillaite is orthorhombic, with an average structure described in Imma, and with a=24.038(8) Aa, b=7.444(3) Aa, c=10.387(3) Aa, V=1858.6(11) Aa (super 3) and Z=4. The structure (wRobs=0.078 for 651 reflections to a resolution of 0.91 Aa) differs most significantly from other walentaite-group members in having an interlayer A2 site occupied. Square-pyramidal polyhedra centred at the A2 sites form edge-shared dimers, (Fe (super 3+) ) (sub 2) O (sub 4) (H (sub 2) O) (sub 4) . The dimers share vertices with TO (sub 4) anions in the layers on either side to form 8-sided channels along [010] occupied by H (sub 2) O molecules.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 84
Serial Issue: 3
Title: The walentaite group and the description of a new member, alcantarillaite, from the Alcantarilla Mine, Belalcazar, Cordoba, Andalusia, Spain
Affiliation: CSIRO Mineral Resources, Clayton South, Victoria, Australia
Pages: 412-419
Published: 202006
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 21
Accession Number: 2020-059320
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N38°34'15" - N38°34'15", W05°03'40" - W05°03'40"
Secondary Affiliation: Mineralogical State Collection, DEU, GermanyAustralian Synchrotron, AUS, AustraliaNatural History Museum of Los Angeles County, USA, United StatesUniversity of Oslo, NOR, Norway
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2020
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