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Zincohoegbomite, a new mineral from eastern Aegean metabauxites

Edwald Ockenga, Unsal Yalcin, Olaf Medenbach and Werner Schreyer
Zincohoegbomite, a new mineral from eastern Aegean metabauxites
European Journal of Mineralogy (December 1998) 10 (6): 1361-1366


The new mineral zincohogbomite, ideally Zn (sub 2-2x) Ti (sub x) Al (sub 4O8) , the Zn-dominant analogue of hogbomite, occurs as an accessory phase in diaspore- or corundum-bearing metabauxites from Samos Island (Greece) and the Menderes Massif (Turkey). It is associated with diaspore or corundum as well as chloritoid, muscovite, paragonite, margarite, titanian hematite, magnetite, ilmenite and gahnite. Zincohogbomite was formed at the expense of gahnite during prograde metamorphism. Single crystals of zincohogbomite initially grown on gahnite {111} faces attain diameters of 0.3 mm. The colour of the mineral is deep brown to black. In thin sections, zincohogbomite is transparent with strong pleochroism (O = dark brown, E = brown). It is uniaxial negative with n (sub o) = 1.878(2) and n (sub e) = 1.832(2) (589 nm), non-fluorescent. Micro-indentation hardness is VHN (sub 100) = 1200 to 1400 kg/mm (super 2) corresponding to about 7 on the Mohs-scale. The calculated density is 4.36 g/cm (super 3) . It is not soluble in HCl, H (sub 2) SO (sub 4) or HNO (sub 3) . Zincohogbomite is hexagonal, most probably P6 (sub 3) mc, with a = 5.708(4) Aa, c = 18.31(2) Aa, V = 516.7(7) Aa (super 3) , Z = 4. The strongest powder diffraction lines are (in Aa, intensities estimated): 2.42 (100), 2.60 (80), 1.425 (80), 1.470 (70), 1.592 (60). Crystal forms are {1014} and {0001}, twinning was not observed. The mean of 10 microprobe analyses of zincohogbomite from the type locality at Kerketefs Mountain/Western Samos is (in wt.%): TiO (sub 2) 5.71, Al (sub 2) O (sub 3) 59.90, Cr (sub 2) O (sub 3) 0.12, FeO 13.85, MgO 0.48, CoO 0.20, NiO 1.01, ZnO 18.87, leading to the formula (based on 8 oxygens) Zn (sub 0.79) Fe (sub 0.65) Mg (sub 0.04) Co (sub 0.01) Ni (sub 0.05) Cr (sub 0.01) Ti (sub 0.24) Al (sub 3.98O8) . The maximum ZnO value encountered is 23.39 wt.%, corresponding to 0.97 Zn per formula unit. The mineral and its name have been approved by the IMA Commission on New Minerals and Mineral Names (No. 94-016).

ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 10
Serial Issue: 6
Title: Zincohoegbomite, a new mineral from eastern Aegean metabauxites
Affiliation: Technischen Universitaet Braunschweig, Institut fuer Geowissenschaften, Braunschweig, Federal Republic of Germany
Pages: 1361-1366
Published: 199812
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 32
Accession Number: 1999-018605
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
N37°37'00" - N37°47'60", E26°34'60" - E27°04'60"
Secondary Affiliation: DMT, DEU, Federal Republic of GermanyRuhr Universitat Bochum, DEU, Federal Republic of Germany
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 199907
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