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Kobokoboite, Al (sub 6) (PO (sub 4) ) (sub 4) (OH) (sub 6) .11H (sub 2) O, a new mineral from the Kobokobo Pegmatite, Democratic Republic of the Congo

Stuart J. Mills, William D. Birch, Anthony R. Kampf and Leopold van Wambeke
Kobokoboite, Al (sub 6) (PO (sub 4) ) (sub 4) (OH) (sub 6) .11H (sub 2) O, a new mineral from the Kobokobo Pegmatite, Democratic Republic of the Congo
European Journal of Mineralogy (March 2010) 22 (2): 305-308


Kobokoboite, ideally Al (sub 6) (PO (sub 4) ) (sub 4) (OH) (sub 6) .11H (sub 2) O, is a new mineral (IMA2009-057), from the Kobokobo pegmatite, South Kivu Province, Democratic Republic of the Congo. Kobokoboite forms 0.1 to 0.15-mm thick crusts and coatings of pearly white, glistening, platy crystals, usually on a matrix of frondelite and keckite. Other associated minerals reported include a fine-grained mixture of planerite, variscite and wavellite ("coeruleolactite"), as well as muscovite-2M (sub 2) , evansite and apatite-(CaOH). Individual crystals of kobokoboite are rectangular plates or flattened blades on (001). The dominant form observed is {001}. The crystals have a pearly lustre, are translucent but transparent on edge, have a white streak and are non-fluorescent. Mohs hardness is about 2 (estimated). The fracture is irregular and the tenacity is brittle. Measured density is 2.21(3); calculated density is 2.287 g cm (super -3) . Kobokoboite crystals are biaxial (-), with the indices of refraction beta =1.558(2) and gamma =1.562(2) measured in white light and with 2V (sub meas.) =60-80 degrees . Orientation: X nearly equal c; Y and Z could not be determined. Crystals are non-pleochroic. The empirical formula (based on (O+OH+F)=33) is: (Al (sub 5.85) Fe (super 3+) (sub 0.14) Ca (sub 0.03) Na (sub 0.02) ) (sub Sigma 6.04) (PO (sub 4) ) (sub 3.97) [(OH) (sub 5.80) F (sub 0.34) ] (sub Sigma 6.14) .10.98H (sub 2) O. Kobokoboite is triclinic, space group P1 or P1, a=7.460(1), b=7.737(1), c=12.385(5) Aa, alpha =102.79(2), beta =90.20(3), gamma =116.33(2) degrees , V=620.6(3) Aa (super 3) and Z=1. The five strongest lines in the powder X-ray diffraction pattern are [d (sub obs) in Aa, (I)]: 11.990, (100); 6.868, (45); 3.552, (39); 6.006, (33); 3.081, (29). The chemistry and cell parameters of kobokoboite suggest a structural relationship with planerite and the new mineral IMA2005-025a, where the same sheet of octahedra and tetrahedra parallel to {001} are responsible for a, b and gamma . The name is in reference to the type locality.

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 22
Serial Issue: 2
Title: Kobokoboite, Al (sub 6) (PO (sub 4) ) (sub 4) (OH) (sub 6) .11H (sub 2) O, a new mineral from the Kobokobo Pegmatite, Democratic Republic of the Congo
Affiliation: University of British Columbia, Department of Earth and Ocean Sciences, Vancouver, BC, Canada
Pages: 305-308
Published: 201003
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 10
Accession Number: 2010-039541
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
S05°04'60" - S03°04'60", E27°07'60" - E27°07'60"
Secondary Affiliation: Museum Victoria, AUS, AustraliaNatural History Museum of Los Angeles County, USA, United States
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201022
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