Beltrandoite, a new root-name in the högbomite supergroup: the Mg end-member magnesiobeltrandoite-2N3S

Magnesiobeltrandoite-2N3S, ideally Mg6Al20Fe3+2 O38(OH)2, is a new member of the h\uf6gbomite supergroup of minerals. It occurs in magnesian chloritites of a metamorphosed layered mafic complex in the Etirol-Levaz continental slice, middle Valtournenche, Aosta Valley, Italy. Magnesiobeltrandoite-2N3S grows in a fine-grained chlorite matrix associated as inclusions to relict pre-Alpine hercynite spinels and dolomite in cm- to dm-long darker boudins, which are cut by corundum\ufeclinochlore \ub1 dolomite veins. It occurs as subhedral to euhedral black crystals ( 3c50\u2013400mm), dark reddish-brown in thin section. It shows dark brown streak and vitreous lustre. It is brittle, with no cleavage observed and uneven fracture. Mohs hardness 486\u20136\ubd. Dcalc = 3.93 g \ub7 cm3. It shows no fluorescence under UV radiation and no cathodoluminescence. The mineral is optically uniaxial (\u2013) with an estimated mean refractive index of ca. 1.80. Pleochroism is weak with e = deep reddish brown (along c axis) and v = reddish brown ( a5 c). Absorption is E > O. The Raman spectrum shows a weak and strongly polarized broad OH-characteristic absorption centred at 3364 cm1. Electron microprobe analysis combined with Synchrotron M\uf6ssbauer source spectrometry yielded the following empirical formula based on 40 anions per formula unit (pfu) [Al18.36Mg3.96Fe2+2:52Fe3+2:08Ti0.56Cr0.40Zn0.06V3+0.03Mn0.02]S28O38(OH)2. The ideal formula is Mg6Al20Fe3+2O38(OH)2.The eight strongest lines in the X-ray powder diffraction pattern are [dobs/A (I) (h k l)]: 2.858 (42) (1 1 0), 2.735 (51) (1 0 7), 2.484 (46) (0 1 8), 2.427 (100) (1 1 5), 1.568 (29) (1 2 8), 1.514 (30) (0 2 12), 1.438 (42) (2 0 13), and 1.429 (72) (2 2 0). The crystal structure of magnesiobeltrandoite-2N3S [P3m1, a = 5.7226(3), c = 23.0231(9)A, V = 652.95(5)A 3] was refined from X-ray single-crystal data to R1 = 0.022; it is isostructural with magnesioh\uf6gbomite-2N3S

Ottensite, brizziite and mopungite from Pereta mine (Tuscany, Italy) : new occurrences and crystal structure refinement of mopungite

Ottensite, Na3 (Sb2O3)(SbS3)\ub73H2O, brizziite, NaSbO3, and mopungite, NaSb(OH)6, have been found on several specimens from the antimony mine of Pereta (Grosseto, Tuscany, Italy). Ottensite from Pereta mine occurs as brilliant reddish-brown spheroidal aggregates, with a diameter up to 0.2 mm, formed by radially oriented individuals. These aggregates are associated with well-shaped tabular and pseudocubic colourless crystals of mopungite and platy aggregates of brizziite. This is the second world occurrence of ottensite and brizziite. The mineral species were characterized by electron microprobe analysis, X-ray diffraction study and microRaman spectroscopy. Single-crystal X-ray diffraction data were collected on a twinned crystal of mopungite and the structure was for the first time refined on a natural sample in space group P42/n [unit cell parameters a = 8.036(3) \uc5, c = 7.926(6) \uc5, V = 511.88(5) \uc53, Z = 4] obtaining an R1-index of 5.17, wR2 of 13.52 and GooF of 1.247

Redefinition of zircophyllite, ideally K2NaMn7Zr2(Si4O12)2O2(OH)4F, a kupletskite-group mineral of the astrophyllite supergroup (in accord with IMA 15-B) as an astrophyllite-group mineral, ideally K2NaFe2+7Zr2(Si4O12)2O2(OH)4F (IMA 17-D)

Zircophyllite is redefined as an astrophyllite-group mineral, ideally K2NaFe2+7Zr2(Si4O12)2O2(OH)4F (Fe2+-dominant at C7) (IMA 17-D). Zircophyllite was previously considered to be a kupletskite-group mineral of the astrophyllite supergroup (Mn2\ufe-dominant at C7), with ideal formula K2NaMn7Zr2(Si4O12)2O2(OH)4F (IMA 15-B). The latter formula is not in agreement with that reported in the original description of zircophyllite

Studtite: primo ritrovamento italiano

This short note reports the first occurrence of studtite [(UO2)O2(H2O)2] 2H2O, which was found during a search on the dumps of the uranium mine of Novazza, Valgoglio, Bergamo, Lombardy

Lobanovite, K2Na(Fe2+4Mg2Na)Ti2(Si4O12)2O2(OH)4, a new mineral of the astrophyllite supergroup and its relation to magnesioastrophyllite

Lobanovite, K2Na(Embedded ImageMg2Na)Ti2(Si4O12)2O2(OH)4, is a new mineral of the astrophyllite supergroup from Mt. Yukspor, the Khibiny alkaline massif, Kola Peninsula Russia. It has been known previously under the following names: monoclinic astrophyllite, magnesium astrophyllite, magnesiumastrophyllite and magnesioastrophyllite but has never been formally proposed and approved as a valid mineral species by the Commission on new Minerals, Nomenclature and Classification of the International Mineralogical Association. It has now been revalidated and named lobanovite after Dr. Konstantin V. Lobanov, a prominent Russian ore geologist who worked in the Kola Peninsula for more than forty years (Nomenclature voting proposal 15-B). Lobanovite has been described from pegmatitic cavities on Mt. Yukspor where it occurs as elongated bladed crystals, up to 0.04\u2005mm wide and 0.2\u2005mm long, with a straw yellow to orange colour. Associated minerals are shcherbakovite, lamprophyllite, delindeite, wadeite, umbite and kostylevite. Lobanovite is biaxial (\u2013) with refractive indices (\u3bb\u2009=\u2009589\u2005nm) \u3b1\u2009=\u20091.658, \u3b2calc.\u2009=\u20091.687, \u3b3\u2009=\u20091.710; 2Vmeas.\u2009=\u200981.5\u201383\ub0. Lobanovite is monoclinic, space group C2/m, a\u2009=\u20095.3327(2), b\u2009=\u200923.1535(9), c\u2009=\u200910.3775(4) \uc5, \u3b2\u2009=\u200999.615(1)\ub0, V\u2009=\u20091263.3(1) \uc53, Z\u2009=\u20092. The six strongest reflections in the powder X-ray diffraction data [d (\uc5), I, (hkl)] are: 3.38, 100, (003); 2.548, 90, (063); 10.1, 80, (001); 3.80, 60, (042,131); 3.079, 50, (132,062); 2.763, 90, (-171). The chemical composition of lobanovite was determined by electron-microprobe analysis and the empirical formula (K1.97Ba0.01)\u3a31.98(Na0.65Ca0.14)\u3a30.79(Fe2+0.18Mg2.02Na1.00Mn0.72)\u3a36.92(Ti1.99Nb0.06)\u3a32.05[(Si8.01Al0.06)\u3a38.07O24]O2(OH)4.03F0.19 was calculated on the basis of 30.2 (O\u2009+\u2009OH\u2009+\u2009F) anions, with H2O calculated from structure refinement, Dcalc.\u2009=\u20093.161\u2005g cm\u20133. In the structure of lobanovite, the main structural unit is the HOH block, which consists of one close-packed O (Octahedral) and two H (Heteropolyhedral) sheets. The M(1\u20134) octahedra form the O sheet and the T4O12 astrophyllite ribbons and [5]-coordinated Ti-dominant D polyhedra link through common vertices to form the H sheet. The HOH blocks repeat along [001], and K and Na atoms occur at the interstitial A and B sites. The simplified and end-member formulae of lobanovite are K2Na[(Fe2+,Mn)4Mg2Na]Ti2(Si4O12)2O2(OH)4 and K2Na(Fe2+4Mg2Na)Ti2(Si4O12)2O2(OH)4, respectively

Ti-rich fluoro-richterite from Kariasen (Norway) : the oxo-component and the use of Ti4+ as a proxy

The crystal-chemical characterization of an amphibole with an unusual composition, A(Na0.76K0.24)B(Ca1.42Na0.56Mn2+0.02) C(Mg2.64Fe2+1.95Mn2+0.07Mg2.64Zn0.01Fe3+0.01Ti4+0.32)T(Si7.18Al0.82)O22W[(OH)0.58O0.27F1.15], found in pegmatitic veins at Kariasen, Larvik Plutonic Complex, Norway, provides an excellent example of the detection and estimation of the oxo component in amphibole. The use of Ti as a proxy for the oxo component is discussed and a procedure to derive accurate Ti partitioning from the results of structure refinement is described. Because the presence and amount of oxo component in amphiboles are important in order to determine values of fO2 and fH2O, especially in igneous and magmatic systems, this procedure should be applied any time the compositional data or the petrological context indicate the presence of significant Ti, or suggest that the oxo component may be a relevant issue