Eur. J. Mineral. 2005, 17, 129–141 Västmanlandite-(Ce) – a new lanthanide- and F-bearing sorosilicate mineral from Västmanland, Sweden: description, crystal structure, and relation to gatelite-(Ce) DAN HOLTSTAM1, UWE KOLITSCH2 and ULF B. ANDERSSON3 1Sektionen för mineralogi, Naturhistoriska riksmuseet, Box 50007, SE-104 05 Stockholm, Sweden Corresponding author, e-mail:
[email protected] 2Institut für Mineralogie und Kristallographie, Universität Wien, Geozentrum, Althanstraße 14, A-1090 Wien, Austria 3Institutionen för geovetenskaper, Uppsala Universitet, Villavägen 16, SE-752 36 Uppsala, Sweden Abstract: Västmanlandite-(Ce), ideally (Ce,La)3CaAl2Mg2[Si2O7][SiO4]3F(OH)2, is a new mineral species from the Västmanland county, Bergslagen region, Sweden. Together with more Fe-rich, F-poor members, it forms solid solutions that are important for lanthanide sequestration in the Bastnäs-type skarn deposits in Västmanland. At the type locality (Malmkärra, Norberg district) it occurs as anhedral grains 0.2–3 mm across, in association with fluorbritholite-(Ce), tremolite, a serpentine mineral, magnetite, dollaseite-(Ce) and dolomite. The mineral is allanite-like in appearance; it is dark brown, translucent, with vitreous luster, and has -3 good cleavage parallel to {001}, uneven to conchoidal fracture, and a yellowish gray streak; Dcalc = 4.51(2) g·cm and Mohs hardness 6. Optically it is biaxial (-), with = 1.781(4), calc = 1.792, = 1.810(4) and 2V = 75(5)°. Chemical analysis by electron-microprobe 57 and Fe Mössbauer spectroscopy yield: La2O3 13.65, Ce2O3 23.90, Pr2O3 2.07, Nd2O3 6.28, Sm2O3 0.42, Gd2O3 0.15, Y2O3 0.18, CaO 4.65, FeO 1.14, Fe2O3 2.69, MgO 5.51, Al2O3 8.58, TiO2 0.04, P2O5 0.05, SiO2 26.61, F 1.06, H2Ocalc 1.61, O ≡ F –0.45, sum 98.14.