ALBERT

Description: Mcalpineite has been found in the Gambatesa mine (eastern Liguria, Italy). It occurs in a quartz vein mainly as yellowish green earthy crusts consisting of poorly crystallized mcalpineite intergrown with an unidentified Cu-Te phase, as well as quite pure aggregates of well euhedral emerald green crystals (individually reaching up to 50 μm), associated with black fragments of paratellurite (TeO 2 ) and weissite (Cu 2–x Te). The chemical formula of this rare mineral, found at the McAlpine mine (type-locality; California, U.S.A.) and at the Centennial Eureka mine (Utah, U.S.A., co-type locality), was originally given Cu 3 TeO 6 ·H 2 O. X-ray powder diffraction and selected-area electron diffraction data of mcalpineite are in good agreement with those of synthetic Cu 3 TeO 6 . In addition no evidence for structural OH group was detected by micro-Raman analysis carried out on samples from Gambatesa, Centennial Eureka, and McAlpine (co-type sample) mines. Taking into account structural, topological, and experimental evidence, the crystal structure and chemical composition of mcalpineite must be revised: the mineral crystallizes in the Ia space group and the correct chemical formula is Cu 3 TeO 6 .

Description: A bstract Bussyite-(Y), ideally (Y, REE ,Ca) 3 (Na,Ca) 6 MnSi 9 Be 5 (O,OH,F) 34 , a new mineral species, was found in the Mont Saint-Hilaire quarry, Quebec, Canada. The crystals are transparent to translucent, dark brown, with a white streak and vitreous luster. Crystals are blocky to prismatic, sometimes radiating, up to 3 mm in size. The mineral is brittle with a perfect { 1{macron} 01} cleavage. Associated minerals include aegirine, analcime, calcite, cappelenite-(Y), catapleiite, charmarite-2 H and -3 T , fluorite, helvine, kupletskite, microcline, perraultite, sérandite, and tainiolite. Bussyite-(Y) is monoclinic, space group C 2, with unit-cell parameters refined from X-ray powder-diffraction data: a 11.545(2), b 13.840(2), c 16.504(4) Å, β 95.87(2)º, V 2623.1(6) Å 3 , and Z = 4. Electron microprobe analysis gave the average composition and ranges, in wt.%: Na 2 O 8.21 (8.43–8.07), K 2 O 0.08 (0.10–0.05), BeO 9.75 (determined by structure refinement), CaO 5.25 (5.36–5.16), MnO 2.93 (3.20–2.57), BaO 0.03 (0.06–0.00), FeO 0.40 (0.60–0.25), Al 2 O 3 0.29 (0.34–0.21), Y 2 O 3 7.58 (7.79–7.37), La 2 O 3 0.48 (0.60–0.40), Ce 2 O 3 2.66 (3.09–2.37), Pr 2 O 3 0.55 (0.64–0.40), Nd 2 O 3 2.85 (2.93–2.81), Sm 2 O 3 1.45 (1.58–1.23), Eu 2 O 3 0.013 (0.17–0.12), Gd 2 O 3 1.97 (2.21–1.57), Tb 2 O 3 0.31 (0.40–0.25), Dy 2 O 3 2.20 (2.46–1.81), Ho 2 O 3 0.39 (0.48–0.33), Er 2 O 3 0.93 (1.07–0.86), Tm 2 O 3 0.16 (0.20–0.12), Yb 2 O 3 0.46 (0.60–0.36), Lu 2 O 3 0.01 (0.01–0.01), Nb 2 O 5 0.20 (0.25–0.15), SiO 2 39.62 (40.03–38.96), ThO 2 2.21 (2.43–1.90), F 3.49 (3.66–3.39), Cl 0.03 (0.03–0.02), H 2 O 5.10 (determined by crystal-structure refinement), O = F + Cl –1.48, total 98.15. The empirical formula based on the crystal-structure analysis showing 34 anions is: 4{(Y 0.874 Nd 0.221 Ce 0.211 Dy 0.154 Gd 0.142 Sm 0.108 Er 0.063 Pr 0.043 La 0.038 Yb 0.030 Ho 0.027 Tb 0.022 Tm 0.011 Eu 0.010 Ca 0.789 Th 0.105 ) 1 [Na 3.442 Ca 0.800 K 0.022 ] 6.055 (Mn 0.537 Fe 0.072 ) 0.899 (Si 8.567 Be 5.065 Al 0.222 ) 13.724 (O 24.107 OH 5.893 ) 30 (F 2.386 OH 1.60.3 Cl 0.011 ) 4 }. The structure was refined to an R 1 index of 0.035 for 6531 unique, observed reflections. The structure has two chemically distinct layers parallel to ( 2{macron} 01): (1) a layer of [(Si,Be)O 4 ] tetrahedra and (2) a large cation Y-,Ca-, Mn-, Na-(O,F) polyhedral layer. Layers are cross-linked through shared O and F atoms. Significant amounts of OH are present, as indicated in the IR spectrum and crystal-structure analysis.

Description: Hydroterskite, ideally Na 2 ZrSi 6 O 12 (OH) 6 , is a new mineral species from the Saint-Amable sill at the Demix-Varennes quarry, near Varennes, Québec, Canada. Hydroterskite crystals are short prismatic in habit, up to 3 mm in width, and bounded by the {100}, {010}, and {001} prisms. The crystals are translucent, pale gray in color, with a white streak and vitreous luster. Hydroterskite is brittle and splintery, with good cleavages on the prismatic planes. It is biaxial negative, α = 1.562 ± 0.002, β = 1.567 ± 0.002, = 1.571 ± 0.002, 2 V meas. = 86(3)°, 2 V calc. = 83°. Dispersion could not be observed, and there is no pleochroism. The optical orientation is X = c , Y = b , and Z = a . The average result of three analyses of a single grain (oxide wt.%) gave Na 2 O 7.82, K 2 O 0.07, CaO 0.62, FeO 0.89, MnO 0.71, Al 2 O 3 0.08, La 2 O 3 0.12, Ce 2 O 3 0.24, SiO 2 59.82, HfO 2 0.11, ThO 2 1.15, ZrO 2 15.00, TiO 2 1.15, Nb 2 O 5 1.12, F 0.11, H 2 O (by stoichiometry) 8.79, for a total (–0.05 O=F) of 96.84. Magnesium, Y, Sr, and Cl were sought but not detected. The empirical formula on the basis of 18 anions with 6 OH – is (Na 1.543 K 0.009 Ca 0.068 La 0.005 Ce 0.009 ) 1.634 (Zr 0.744 Ti 0.088 Nb 0.052 Th 0.005 Hf 0.003 Fe 0.076 Mg 0.002 Mn 0.061 Al 0.010 ) 1.041 Si 6.087 O 12 (OH 5.963 F 0.035 Cl 0.002 ) 6 . The structure of hydroterskite is orthorhombic in the centric space group Pnca , with a 13.956(6), b 14.894(7), c 7.441(4) Å, V 1546.8(2.0) Å 3 , and Z = 4. It has been refined to an R index of 0.036 on the basis of 1080 observed reflections. There are two crystallographically distinct Na sites, both with eight-fold co-ordination: [ Na1 O 6 (OH) 2 ] is a hexagonal dipyramid polyhedron, whereas [ Na2 O 6 (OH) 2 ] is a bifurcated pentagonal dipyramid. The Zr atom is in a regular octahedral coordination. Silicon, in tetrahedral coordination with oxygen, forms spiral chains parallel to the c axis. These chains are cross-linked by edge-sharing [ZrO 6 ] octahedra and [NaO 8 ] polyhedra. All three H atoms were located. The crystal-structure determination of terskite in the literature was most likely incorrectly assigned to an acentric space-group. The hydroterskite crystal structure is compared to the structures of terskite, elpidite, and yusupovite.

Description: The crystal chemistry of a unique Nb-Ti-rich thorite from Mont Saint-Hilaire (Quebec) has been examined by a combination of single crystal and powder X-ray diffraction, electron microprobe analyses, and Fourier-transform infrared spectroscopy. The average of 9 compositions gave (Th 0.21 Nb 0.20 Ti 0.18 Ca 0.13 Y 0.10 REE 0.09 Fe 0.03 Zr 0.01 Sr 0.01 Mn 0.01 K 0.01 Na 0 . 01 ) 1.00 [(Si 0.49 0.41 Al 0.08 P 0.01 S 0.01 ) 1.00 (O 2.33 F 0.02 )](OH) 1.70 . This is the first example in the literature of a zircon-group mineral containing elevated concentrations of Nb (0.20 apfu , 13.33 wt.% Nb 2 O 5 ) and Ti (0.19 apfu Ti, 7.41 wt.% TiO 2 ), and evidence for the (SiO 4 ) 4– (OH) 4 4– "hydrogarnet" substitution. The crystal structure was solved and refined to R = 3.40% and wR 2 = 9.73% for 68 reflections with F o 〉 4( F o ). The studied thorite is slightly metamict, tetragonal, space group I 4 1 / amd , with a 7.058(1) Å, c 6.2260(12) Å, V 310.15(11) Å 3 , and Z = 4. It is isostructural with other zircon-group minerals and has a unit cell which is 4% smaller than that of thorite sensu stricto , a result of the incorporation of high field-strength elements of smaller radii. The structure consists of one eight-coordinated metal site ( A = Th, Zr, U, REE, Y, Nb, Ti, etc. ), one tetrahedral site ( T ), one O site, and one variably-occupied H site. The A site is coordinated by four axial O atoms [ A –O axial = 2.428(5) Å] and four equatorial O atoms [ A –O eq = 2.322(6) Å], which define a bisdisphenoid with 〈 A –O〉 = 2.374 Å. The T site in MSH thorite is only partially occupied by Si (33% vacant) and coordinated by four O with T –O = 1.641(5) Å. A partially occupied H site (31%) is located 0.980 Å away from the O atom, forming (O 4 H 4 ) 4– groups when the T site is vacant. Removal of the center of symmetry in the structure allows for the possibility of the presence of bimodal T –O and A –O bond lengths, leading to both short Si–O bonds and longer –OH bonds, as well as the shorter A –O bonds required for Nb and Ti. Accommodation of Nb and Ti into the thorite structure may be facilitated by increased distortion of the A O 8 bisdisphenoid, relaxation and shortening of A –O bonds as a result of the (SiO 4 ) 4– (OH) 4 4– substitution, and the likely presence of defects (O vacancies) in regions which have undergone slight metamictization, resulting in short-range ordering of Nb, Ti, and Th. Although it is possible that a metastable, limited solid solution exists between thorite and (OH) 4 4– -dominant "thorogummite" with intermediate compositions defined by Th(SiO 4 ) 1 –x (OH) 4 x , reported compositions indicate otherwise and it is suggested that the name "thorogummite" be abandoned.

Description: A bstract Serendibite, Ca 1.93 Na 0.08 Mg 2.58 Al 5.03 B 1.53 Si 2.71 O 20 , was recently discovered in a lens of B-rich calc-silicate rock metamorphosed at 6–7 kbar, 650–700 °C in the Central Metasedimentary Belt, Grenville Province. Based on paragenesis and tourmaline composition, which were used to monitor changes in fluid composition, the following stages of mineralization are recognized: (1) a prograde assemblage consisting of K-feldspar, tourmaline [T1 with X Ca = Ca/(Ca + Na) = 0.54, T2 with X Ca = 0.71], and calcite, inferred from relicts in scapolite; (2A) a peak metamorphic assemblage of aluminous diopside, serendibite, lesser phlogopite, and local scapolite (Me 62 ); (2B) continued formation of phlogopite around serendibite in calcite pockets although serendibite was stable; and (3) high-temperature breakdown of serendibite to uvite (T3; X Ca = 0.82) + spinel + calcite, and of aluminous diopside to pargasite. Three generations of idiomorphic magnesian tourmaline that crystallized in calcite pockets (T4 to T6) recorded fluid evolution as follows: (A) X Ca 0.5 and relatively moderate Ti concentrations (generation T4); (B) increase in Na relative to Ca, X Ca 0.3 (generation T5), with the rare occurrence of oligoclase ( X Ca = 0.17) and relatively low Ti concentrations; and (C) X Ca 0.5, relatively high Ti concentrations (generation T6). The final stage is localized, low-temperature alteration to fine-grained phyllosilicates. The boron isotopic composition of peak metamorphic serendibite ( 11 B = +4.3 ± 1.7) is lower than that of prograde tourmaline ( 11 B = +10.6 ± 2.3) from which it formed. The fractionation difference between serendibite and metamorphic fluid (with B derived from prograde tourmaline), 11 B Srd–Tur = 11 B Srd – 11 B Tur = –6.3, is similar to the ab initio calculated fractionation factor between serendibite and fluid ( 11 B Srd–fluid = –7.6 ± 1.4 at 727 °C). Tetrahedral boron coordination in serendibite is largely responsible for this fractionation. High-temperature uvite replacement of serendibite is significantly higher in 11 B relative to serendibite (+10.6 versus +4.3), which is attributed to buffering of boron isotopes by serendibite in local equilibrium with uvite. Tourmalines formed in calcite pockets range from +8 to almost +12 on average, while the core of a T4 tourmaline has 11 B = +3.4. This low 11 B value is attributed to a temporary departure from equilibrium due to fluid influx. The boron isotope signature of prograde tourmaline suggests a marine evaporite source.

Description: A bstract The crystal structure of mammothite, Pb 6 Cu 4 AlSbO 2 (SO 4 ) 2 Cl 4 (OH) 16 , is monoclinic in acentric space group C 2, with a 18.959(4), b 7.3398(19), c 11.363(3) Å, β 112.428(9){ring}, V 1461.6(1.0) Å 3 , and Z = 2. It has been refined to an R index of 0.019 on the basis of 3878 observed reflections. There are three crystallographically distinct Pb sites with two different co-ordinations: [Pb1O 8 Cl 1 ] is a mono-capped square antiprism polyhedron, while [Pb21O 7 Cl 2 ] and [Pb22O 7 Cl 2 ] are tri-capped trigonal prisms. Both Cu 2+ sites have distorted [4 + 2] octahedral coordination due to the Jahn-Teller effect. The Al and Sb sites are regular-octahedral co-ordination with oxygen atoms. The [SO 4 ] tetrahedron is quite distorted, with S–O bond lengths varying from 1.45 to 1.52 Å and subtended O–S–O angles varying from 106 to 113{ring}. In the structure there are eight (OH) – anions. All eight H atoms pfu were located, and it is these structure sites that reduce the symmetry from centric to acentric. Although mammothite is classified as a framework structure, it has a distinct layering. There are two layer types in the mammothite structure that parallel (001). There are three octahedrally coordinated sites; two are occupied by Cu atoms and one by an Al atom, in the octahedral layer. The tetragonal dipyramids [CuØ 6 ] are linked forming ‘olivine-like’ chains parallel to the b -axis. The second layer, termed the cross-linked layer, has three [PbØ 9 ] polyhedra with shared edges forming chains parallel to the b -axis, like the [CuØ 6 ] tetragonal dipyramids. These chains are cross-linked by edge-sharing [SbO 6 ] octahedra and decorated with [SO 4 ] groups. The H atoms are in ‘holes’ within both layers.

Description: A bstract Thorogummite has been discredited as a valid mineral species. No type material from the original study was available for analysis. An extensive review of the literature, both recent and historic, reveals the use of the name "thorogummite" for any hydrated, metamict thorite or unidentified alteration product of a Th-bearing mineral. All early studies on "thorogummite" and other alteration products of thorite were performed on heterogeneous mixtures of mostly secondary and metamict materials and must be considered suspect. The validity of Frondel’s (1953) proposed (SiO 4 ) 4– (OH) 4 4– substitution between thorite and thorogummite was examined and shown to be an incomplete solid solution. All compositions in the literature to date are Th- and Si-dominant and must be considered thorite. Furthermore, the majority of the compositions in the literature are outdated and likely do not represent those from crystalline, single-phases. More likely, all so-called "thorogummite" are simply metastable hydrated or metamict thorite with varying volumes of other alteration products. The discreditation has been approved by the IMA Commission on New Minerals, Nomenclature and Classification (Nomenclature Voting proposal 14-B).