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New compositional and structural data validate the status of jamborite

Luca Bindi, Andrew G. Christy, Stuart J. Mills, Marco E. Ciriotti and Erica Bittarello
New compositional and structural data validate the status of jamborite (in A tribute to John Leslie Jambor, Robert F. Martin (prefacer))
The Canadian Mineralogist (September 2015) 53 (5): 791-802

Abstract

Jamborite was originally described with the formula (Ni (super 2+) ,Ni (super 3+) ,Fe)(OH) (sub 2) (OH,S,H (sub 2) O) from Ca' de' Ladri and Monteacuto Ragazza near Bologna, and Castelluccio di Moscheda near Modena, Italy. Re-examination of the mineral from the type localities and Rio Vesale, Sestola, Val Panaro (Emilia-Romagna, Italy), led to the discovery of a crystal suitable for study by single-crystal and powder X-ray diffraction, SEM-EDS, and Raman spectroscopy. Jamborite crystallizes in the space group R3m, with the unit-cell parameters a 3.068(4) A, c 23.298(11) A, and Z = 3. The structure refinement (R (sub 1) = 0.0818) showed that jamborite contains brucite-like sheets of edge-sharing octahedra (Ni (super 2+) ,M (super 3+) )(O,OH) (sub 6) with a distinctive double layer of partially occupied H (sub 2) O molecules between them. Raman data indicate that the sulfur is present as sulfate rather than sulfide. The new analytical data were recalculated on the basis of 1 (Ni+Ca+Co+Fe) to give the formula [(Ni (super 2+) (sub 0.902) Ca (super 2+) (sub 0.002) )(Co (super 3+) (sub 0.072) Fe (super 3+) (sub 0.024) )] (sub Sigma 1.000) (OH) (sub 1.884) Cl (sub 0.012) (H (sub 2) O) (sub 0.004) (SO (sub 4) ) (sub 0.100) .0.900H (sub 2) O. The sulfur occupancy was too low to be located in the refinement, but the approximately 1:1 ratio of M (super 3+) :S from the chemical analysis implies that SO (sub 4) (super 2-) replaces OH (super -) in the brucite sheet rather than sitting in the interlayer space. The splitting of the H (sub 2) O layer allows avoidance of short SO (sub 4) (super 2-) . .H (sub 2) O distances. Thus, jamborite is not a member of the hydrotalcite supergroup. Jamborite is redefined as M (super 2+) (sub 1-x) M (super 3+) (sub x) (OH) (sub 2-x) (SO (sub 4) ) (sub x) .nH (sub 2) O, where M (super 2+) is dominantly Ni, M (super 3+) is dominantly Co, x < or = 1/3 and probably < or = 1/7 (x = 0.10 for the neotype sample), and n <(1-x). The low M (super 3+) /M (super 2+) ratio relative to honessite and hydrohonessite and high Co content may explain the rarity of jamborite as an early alteration product of millerite. The redefinition of jamborite and designation of the neotype specimen from Rio Vesale have been approved by the Commission on New Minerals, Nomenclature and Classification (CNMNC), voting proposal 14-E.


ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 53
Serial Issue: 5
Title: New compositional and structural data validate the status of jamborite
Title: A tribute to John Leslie Jambor
Affiliation: Universita degli Studi di Firenze, Dipartimento di Scienze della Terra, Florence, Italy
Affiliation: McGill University, Montreal, QC, Canada
Pages: 791-802
Published: 201509
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 14
Accession Number: 2016-094376
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
N43°45'00" - N45°10'00", E09°10'00" - E12°49'60"
Secondary Affiliation: Australian National University, AUS, AustraliaMuseum Victoria, AUS, AustraliaAssociazione Micromineralogica Italiana, ITA, ItalyUniversita degli Studi di Torino, ITA, Italy
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201646
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