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- Title
Igelströmite, Fe3+(Sb3+Pb2+)O4, and manganoschafarzikite, Mn2+Sb23+O4, two new members of the newly established minium group, from the Långban Mn–Fe deposit, Värmland, Sweden.
- Authors
Holtstam, Dan; Langhof, Jörgen; Friis, Henrik; Karlsson, Andreas; Erambert, Muriel
- Abstract
The two new minerals igelströmite, Fe 3+ (Sb 3+ Pb 2+)O 4 , and manganoschafarzikite, Mn 2+ Sb 23+ O 4 , are found in the Långban Fe–Mn deposit, in open fractures in a fine-grained hematite ore, with minor amounts of aegirine, a serpentine-group mineral, fluorcalcioroméite, baryte, nadorite, mimetite and other late-stage minerals. Igelströmite is named after the Swedish geologist–mineralogist Lars Johan Igelström (1822–1897). Mohs hardness = 3–4 and Dcalc= 6.33(1) and 5.37(2) g cm -3 for igelströmite and manganoschafarzikite, respectively. Cleavage is distinct on {110}. Both minerals are brittle, with an uneven to conchoidal fracture. The chemical formulae obtained from microprobe data are (Fe 0.593+ Mn 0.292+ As 0.063+ Fe 0.062+)Σ=1.00 (Sb 1.243+ Pb 0.652+ As 0.113+)Σ=2.00 O 4 and (Mn 0.642+ Fe 0.252+ Mg 0.08)Σ=0.97 (Sb 1.973+ As 0.033+ Pb 0.012+)Σ=2.01 O 4. The crystal structures for igelströmite and manganoschafarzikite have been refined in space group P 4 2 /mbc from single-crystal X-ray diffraction data to R 1 = 3.73 % and 1.51 %, respectively, giving the following sets of unit-cell parameters: a= 8.4856(2), 8.65159(8) Å; c= 6.0450(3), 5.97175(9); and V= 435.27(3), 446.986(11) Å 3 for Z = 4. Both minerals are isostructural with minium, Pb 4+ Pb 22+ O 4 , where Pb 4+ O 6 forms distorted octahedra, which connect via trans-edges to form rutile-like ribbons along c. The Pb 2+ atoms appear in trigonal, flattened PbO 3 pyramids, which are linked via corners to form zigzag (PbO 2)n chains. The minium group, of general formula MX2 O 4 (X= As 3+ , Sb 3+ , Pb 2+), presently consists of the minerals minium, trippkeite, schafarzikite, igelströmite and manganoschafarzikite. For future new members, it is recommended to consider the X cation content for the root name and add prefixes to indicate the dominant metal at the M position.
- Subjects
CHEMICAL formulas; COMPOUND fractures; SPACE groups; BARITE; RUTILE; HEMATITE; CRYSTAL structure
- Publication
European Journal of Minerology, 2024, Vol 36, Issue 2, p311
- ISSN
0935-1221
- Publication type
Article
- DOI
10.5194/ejm-36-311-2024