Titre du document / Document title

Tsumgallite, GaO(OH), a new mineral from the Tsumeb mine, Tsumeb, Namibia

Auteur(s) / Author(s)

SCHLüTER Jochen ; KLASKA Karl-Heinz ; ADIWIDJAJA Gunadi ; GEBHARD Georg ;

Résumé / Abstract

The new mineral tsumgallite is a gallium oxide hydroxide, has the ideal chemical formular GaO(OH), is orthorhombic, space group Pbnm, with a = 4.512(5) Å, b = 9.772(8) Å, c = 2.967(4) Å, cell volume 130.8(2) Å₃, Z = 4, from powder data. Cell parameter refined from powder data with the structure of α-gallium oxide deuteriohydroxide give a = 4.517 Å, b = 9.760 Å, c = 2.964 Å, volume 130.7 Å₃. Tsumgallite is isostructural to goethite and diaspore. The strongest reflections in the X-ray powder diffraction data are as follows: (d^meas.(Å),I,(hkl)): 4.089(100)(110), 2.404(100)(111), 2.632(33)(130), 1.690(26)(221) and 2.530(22) (021). Tsumgallite was found at the Tsumeb mine, Tsumeb, Namibia. It forms tiny mica-like aggregates less than 1 mm across. Individual thin, platy crystals do not exceed 40 μm in size. The colour is a pale greenish yellow to beige. Tsumgallite is associated with of söhngeite and zincian siderite in vugs of a tennantite-germanite ore. Chemical analyses by electron microprobe gave Ga²O³ 78.13, Fe²O³ 3.99, GeO² 4.01, ZnO 0.78, SiO² 1.07, H²O^(ideal) 8.77, sum 96,75 weight %, where the amount of water was taken from the ideal composition. The resulting empirical formular calculated on the basis of 2 anions is (Ga^0.86, Fe₃₊0.05, Ge^0.04, Si^0.02, Zn^0.01)^Σ0.98 O(OH)^1.01. The mineral was named for the type locality and its chemical composition. Tsumgallite has been approved by the I.M.A. Commission on New Minerals and Mineral Names.

Revue / Journal Title

Neues Jahrbuch für Mineralogie Monatshefte   ISSN 0028-3649   CODEN NJMMAW 

Source / Source

2003, n^o11, pp. 521-527 [7 page(s) (article)]

Langue / Language

Anglais
Revue : Multilingue

Editeur / Publisher

Schweizerbart'sche, Stuttgart, ALLEMAGNE  (1950-2004) (Revue)

Localisation / Location

INIST-CNRS, Cote INIST : 924 A, 35400011979011.0030