Explore the vast range of titles available.

A new member of the gadolinite supergroup, gadolinite-(Nd), IMA2016-013, ideally Nd2FeBe2Si2O10, was found in the Malmkarra mine, ∼3.5 km WSW of Norberg, south-central Sweden, where it occurs in association with fluorbritholite-(Ce), vastmanlandite-(Ce), dollaseite-(Ce), bastnasite-(Ce) and tremolite. Gadolinite-(Nd) forms anhedral grains up to 150 µm in size, commonly occurring as aggregates of olive green colour. The crystals are transparent with vitreous to adamantine lustre. Gadolinite-(Nd) is brittle with conchoidal fracture, no cleavage or parting was observed. It has a white streak, the Mohs hardness is 6.5-7 and the calculated density is 4.86 g cm-3. Optically, the mineral is weakly pleochroic in shades of olive green, biaxial (-), nα = 1.78(1), nβ(calc.) = 1.80, nγ = 1.81(1) measured in white light, 2V(meas.) = 62(3)°. Electron-microprobe and laser ablation inductively coupled plasma mass spectrometry analysis [in wt.%] provided SiO2 21.77, Y2O3 5.49, La2O3 2.78, Ce2 O3 14.04, Pr2O3 3.28, Nd2O3 19.27, Sm2O3 5.30, Eu2O3 0.24, Gd2O3 4.10, Tb2O3 0.36, Dy2O3 1.32, Ho2O3 0.18, Er2O3 0.38, MgO 0.51, CaO 0.14, MnO 0.10, FeO 10.62, B2O3 0.10, BeOcalc. 8.99, H2Ocalc. 0.55 and total 99.52 giving the following empirical formula (based on 2 Si): (Nd0.632 Ce0.472Y0.268Sm0.168Gd0.125Pr0.110La0.094Dy0.039Ca0.014 Er0.011 Tb0.011Eu0.008Ho0.008)Σ1.957(Fe0.816Mg0.070Mn0.008) Σ0.894(Be1.984B0.016)Σ2.000Si2O9.660OH0.337. A weak Raman vibration band at ∼3525 cm-1 confirms the presence of water in the structure. Gadolinite-(Nd) is monoclinic, P21/c, with a = 4.8216(3) Å, b = 7.6985(4) Å, c = 10.1362(6) Å, β = 90.234(4)°, V = 376.24(6) Å3 and Z = 2. The strongest X-ray diffraction lines are [dobs in Å (hkl) Irel]: 4.830 (100) 72, 3.603 (021) 37, 3.191(-112) 52, 3.097 (013) 35, 2.888 (121) 100, 2.607(113) 49, 2.412 (200) 24. Along with the Malmkarra mine, gadolinite-(Nd) was also recorded also at Johannagruvan and Nya Bastnas. The minerals of the gadolinite subgroup together with fluorbritholite-(Ce) incorporate the highest fraction of medium-to-heavy rare-earth elements among associated rare-earth element minerals in the Malmkarra mine and possibly in all Bastnas-type deposits.

Åsgruvanite-(Ce), ideally Ce16Ca5Al(SiO4)6(AsO3)8(CO3)2Cl3(ClF3)(OH)2, is a new mineral species (IMA–CNMNC 2025-004) from the Åsgruvan Fe-skarn deposit, Norberg, Västmanland, Sweden, which is directly related to the Bastnäs type of rare earth element (REE) mineralisations in the Palaeoproterozoic Bergslagen ore province. Åsgruvanite-(Ce) occurs as anhedral, occasionally elongated grains up to 400 µm. It is greyish green to nearly colourless, with a white streak and a vitreous to greasy lustre. Cleavage is distinct on 001 and less so on 100; the mineral is brittle, and its fracture is uneven. The calculated density is 4.79(1) g cm−3. Åsgruvanite-(Ce) is optically uniaxial (+), with a refractive index above 1.8; the calculated average is 1.88 (Gladstone–Dale approach). Åsgruvanite-(Ce) crystallises in the trigonal system in space group P-3m1 (Z=1), with the following unit cell parameters: a=10.5728(6) Å and c=15.0899(11) Å. Åsgruvanite-(Ce) occurs in a magnetite–REE skarn, but its formation postdates the groundmass carbonate and skarn assemblage, and it is associated with late-stage calcite, dolomite, a dollaseite-like allanite group mineral, gadolinite-(Y/Nd), and a fluorocarbonate related to bastnäsite-(Ce), with variable F contents. The structure was refined to R1=6.23 % for 987 reflections. It is unique and consists of two alternating layers, A and B, along the c axis. Layer A (∼8.4 Å) has the composition [(Ce12Ca3)AlSi6(C1.50S0.50)Σ2.00O30(OH)2]15+. Layer B (∼6.7 Å) corresponds to the composition [(Ce4Ca2)As83+O24Cl4F3]15−. These layers form tunnel-like features parallel to [100], which are partially occupied by Cl atoms. Spectroscopic data (infrared and micro-Raman) support the structural model.