Authors: Holtstam D.¹; Nysten P.²; Gatedal K.³

Source: Mineralogical Magazine, Volume 62, Number 3, 1 June 1998 , pp. 395-407(13)

Publisher: Mineralogical Society

Abstract:

The Långban, Nordmark and Jakobsberg Mn-Fe deposits contain the only known occurrences of filipstadite and manganostibite (ideal formulae (Mn, Mg)₂(Sb⁵⁺_0.5Fe³⁺_0.5)O₄ respectively). Filipstadite from Nordmark is newly recognized, and occurs in assemblages with svabite-johnbaumite, calcite, tephroite-forsterite, phlogopite-kinoshitalite, tilasite, ±jacobsite, ±plumbian roméite, ±adelite, ±hedyphane. Manganostibite from Långban and Jakobsberg is reported for the first time, and the mineral is generally associated with katoptrite, tephroite, humite-group minerals, calcite, svabite, allactite, manganosite, hausmannite, jacobsite, spinel s.s., etc. Whereas filipstadite is clearly secondary relative to the major part of the matrix components, manganostibite is believed to have formed coevally with the principal ore and skarn minerals at these deposits. The previously known compositional ranges are extended. Based on electron-microprobe analyses, Nordmark filipstadite contains 4.1-7.3 MgO, 0.0-0.5 Al₂O₃, 30.5-45.3 MnO, 17.0-40.1 Fe₂O₃, 0.2-0.9 ZnO, 19.9-29.9 Sb₂O₅ (all in wt.%), corresponding to 58-100 mol.% of a pure filipstadite component. Associated jacobsites show Sb₂O₅ contents of up to c. 5 wt.%. Manganostibites (all three deposits considered) contain 1.0-2.9 MgO, 2.8-3.8 SiO₂, 57.4-60.3 MnO, 0.2-3.5 Mn₂O₃, 0.3-2.0 Fe₂O₃, 0.0-2.4 ZnO, 21.5-23.0 Sb₂O₅, 7.7-10.0 As₂O₅ (all in wt.%). Si and trivalent cations are incorporated via a (Mn³⁺,Fe³⁺) + Si⁴⁺ = Mn²⁺ + As⁵⁺ exchange mechanism, which improves the local charge balance at tetrahedral structural sites dominated by As.

Keywords: FILIPSTADITE; MANGANOSTIBITE; JACOBSITE; KATOPTRITE; ANTIMONY; LANGBAN; NORDMARK; JAKOBSBERG; SWEDEN

Language: English

Document Type: Research article

Affiliations: 1: Department of Mineralogy, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden 2: Institute of Earth Sciences, Uppsala University, Villava ¨gen 16, SE-752 36 Uppsala, Sweden 3: Xenos Mineral, Ra gva ¨gen 7, SE-713 34 Nora, Swedengva ¨gen 7, SE-713 34 Nora, Sweden">

Publication date: 1998-06-01

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