ALBERT

Description: The new mineral species barlowite, ideally Cu 4 FBr(OH) 6 , has been found at the Great Australia mine, Cloncurry, Queensland, Australia. It is the Br and F analogue of claringbullite. Barlowite forms thin blue, platy, hexagonal crystals up to 0.5 mm wide in a cuprite-quartz-goethite matrix associated with gerhardtite and brochantite. Crystals are transparent to translucent with a vitreous lustre. The streak is sky blue. The Mohs hardness is 2–2.5. The tenacity is brittle, the fracture is irregular and there is one perfect cleavage on {001}. Density could not be measured; the mineral sinks in the heaviest liquid available, diluted Clerici solution ( D 3.8 g/cm 3 ). The density calculated from the empirical formula is 4.21 g/cm 3 . Crystals are readily soluble in cold dilute HCl. The mineral is optically non-pleochroic and uniaxial (–). The following optical constants measured in white light vary slightly suggesting a small variation in the proportions of F, Cl and Br: 1.840(4)–1.845(4) and 1.833(4)–1.840(4). The empirical formula, calculated on the basis of 18 oxygen atoms and H 2 O calculated to achieve 8 anions and charge balance, is Cu 4.00 F 1.11 Br 0.95 Cl 0.09 (OH) 5.85 . Barlowite is hexagonal, space group P 6 3 / mmc , a = 6.6786(2), c = 9.2744(3) Å, V = 358.251(19) Å 3 , Z = 2. The five strongest lines in the powder X-ray diffraction pattern are [ d (Å)( I )( hkl )]: 5.790(100)(010); 2.889(40)(020); 2.707(55)(112); 2.452(40)(022); 1.668(30)(220).

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: Billwiseite, ideally Sb 3+ 5 (Nb,Ta) 3 WO 18 , is an oxide mineral from a granitic pegmatite on the eastern margin of the Nanga Parbat – Haramosh massif at Stak Nala, 70 km east of Gilgit, Pakistan. It is transparent, pale yellow (with a tinge of green), has a colorless to very pale-yellow streak, a vitreous luster, and is inert to ultraviolet radiation. Crystals are euhedral with a maximum size of 0.5 x 0.25 x 0.15 mm and show the following forms: {100} pinacoid {011} pinacoid {410} prism; contact twins on (100) are common. Cleavage is {100} indistinct, Mohs hardness is 5, and billwiseite is brittle with a hackly fracture. The calculated density is 6.330 g/cm 3 . The indices of refraction were not measured; the calculated index of refraction is 2.3, 2 V ( obs ) = 76(2)°. Billwiseite is colorless in transmitted light, non-pleochroic, and the optic orientation is as follows: X || b , Y ^ c = 72.8° (in β acute). It occurs scattered across the surface of a large (5 x 2.5 x 1.3 cm) crystal of lepidolite from a miarolitic cavity. The most abundant minerals in the cavities at Stak Nala are albite, quartz, K-feldspar, tourmaline, muscovite or lepidolite, topaz and fluorite, and billwiseite can be partly mantled by B-rich muscovite. Billwiseite is monoclinic, space group C 2/ c , a 54.116(5), b 49143(5), c 5.5482(5) Å, β 90.425(2)°, V 1475.5(2) Å 3 , Z = 4, a:b:c = 11.012 : 1 : 1.131. The strongest seven lines in the X-ray powder-diffraction pattern [ d in Å( I ) hkl ] are as follows: 3.147(100)(91, 911), 3.500(55) (51, 511), 1.662(53)( 14 2), 3.017(48)( 18 00), 1.906(47)( 18 20), 1.735(30)(11, 113), 1.762(25)( 27 1, 27 11). Chemical analysis by electron microprobe gave Nb 2 O 5 12.03, Ta 2 O 5 19.31, Sb 2 O 3 48.34, TiO 2 0.99, WO 3 19.96, sum 100.63 wt.% where the valence state of Sb was determined by crystal-structure analysis. The resulting empirical formula on the basis of 18 O anions is Sb 3+ 4.87 (Nb 1.33 Ta 1.28 Ti 0.18 W 1.26 ) 4.05 O 18 . The crystal structure of billwiseite was solved by direct methods and refined to an R 1 index of 4.71% based on 2122 observed reflections collected on a three-circle diffractometer with Mo K α X-radiation. The structure consists of two distinct sheets of M (= Ta,Nb,W) octahedra and three distinct sheets of Sb 3+ polyhedra parallel to (100). These sheets alternate in the a direction to form a continuous structure.

Description: Aspedamite, ideally 12 (Fe 3+ ,Fe 2+ ) 3 Nb 4 [Th(Nb,Fe 3+ ) 12 O 42 ]{(H 2 O),(OH)} 12 , is a new heteropolyniobate mineral species from the Herrebøkasa quarry, Aspedammen, Østfold, southern Norway. It occurs as small euhedral crystals of dodecahedra and cubes to a maximum of 50 μm across, perched on a white mat of an Al–Nb–Fe–Ti–Ca–K-bearing silicate on a partly altered 12 x 12 x 6 mm crystal of monazite penetrated by plates of columbite-(Fe) and muscovite. Aspedamite is brownish orange with a very pale orange streak and an adamantine luster; it does not fluoresce under ultraviolet light. The Mohs hardness is 3–4, and it is brittle with a hackly fracture. The calculated density is 4.070 g/cm 3 , and the calculated index of refraction is 2.084. Aspedamite is cubic, space group Im , a 12.9078(6) Å, V 2150.6(3) Å 3 , Z = 2. The strongest seven lines in the X-ray powder-diffraction pattern [ d in Å( I ) hkl ] are: 9.107(100)011, 2.635(36)224, 2.889(33)024, 1.726(29)246, 3.233(28)004, 3.454(18)123, 4.567(15)022. A chemical analysis with an electron microprobe gave Nb 2 O 5 65.64, Ta 2 O 5 1.78, SiO 2 0.78, ThO 2 5.64, TiO 2 2.15, Fe 2 O 3 10.56, FeO 2.73, MnO 0.82, CaO 0.28, K 2 O 0.16, La 2 O 3 0.52, Ce 2 O 3 1.62, Nd 2 O 3 0.44, H 2 O (calc) 7.20, sum 100.32 wt.%; the H 2 O content was determined by crystal-structure analysis. The empirical formula of aspedamite on the basis of 54 anions with Fe 3+ /(Fe 3+ + Fe 2+ ) = 0.67 (estimated from crystal-chemical arguments) and O(4) = (H 2 O) 9 + (OH) 3 is K 0.09 Ca 0.13 Ce 0.26 La 0.08 Nd 0.07 Fe 2+ 1.00 Mn 0.30 Fe 3+ 3.48 Th 0.56 Ti 4+ 0.71 Si 0.34 Nb 12.98 Ta 0.21 O 42 (H 2 O) 9 (OH) 3 . The crystal structure of aspedamite was solved by direct methods and refined to an R 1 index of 1.6% based on 596 observed reflections collected on a three-circle rotating-anode (Mo K α X-radiation) diffractometer equipped with multilayer optics and an APEX-II detector. The structure is based on the heteropolyanion [ DA 12 O 42 ] ( D = Th, sum A = Nb 9 Fe 3+ 2 Ti), which consists of twelve face- and corner-sharing AO 6 octahedra that surround the [12]-coordinated D cation. There are eight heteropolyanions at the corners of the unit cell, with an additional heteropolyanion at the center, forming an I -centered arrangement. Each heteropolyhedral cluster is decorated by eight B octahedra, each of which bridges two adjacent clusters along the body diagonals of the cell. Further intercluster linkage is provided by the C octahedra, which link pairs of adjacent clusters in the a direction. Aspedamite is isostructural with menezesite.

Description: Ianbruceite, ideally [Zn2(OH)(H2O)(AsO4)](H2O)2, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as thin platy crystals up to 80 μm long and a few μm thick, which form flattened aggregates up to 0.10 mm across, and ellipsoidal aggregates up to 0.5 mm across. It is associated with coarse white leiteite, dark blue köttigite, minor legrandite and adamite. Ianbruceite is sky blue to very pale blue with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. It has perfect cleavage parallel to (100), is flexible, and deforms plastically. The Mohs hardness is 1 and the calculated density is 3.197 g cm−3. The refractive indices are α = 1.601, β = 1.660, γ = 1.662, all ±0.002; 2Vobs = 18(2)°, 2Vcalc = 20°, and the dispersion is r 〈 v, weak. Ianbruceite is monoclinic, space group P21/c, a = 11.793(2), b = 9.1138(14), c = 6.8265(10) Å, β = 103.859(9)°, V = 712.3(3) Å3, Z = 4, a:b:c = 1.2940:1:0.7490. The seven strongest lines in the X-ray powder diffraction pattern [d (Å), I, (hkl)] are as follows: 11.29, 100, (100); 2.922, 17, (130); 3.143, 15, (2İ02); 3.744, 11, (300); 2.655, 9, (230); 1.598, 8, (1İ52); 2.252, 7, (222). Chemical analysis by electron microprobe gave As2O5 36.27, As2O3 1.26, Al2O3 0.37, ZnO 49.72, MnO 0.32, FeO 0.71, K2O 0.25, H2Ocalc 19.89, sum 108.79 wt.%; the very high oxide sum is due to the fact that the calculated H2O content is determined from crystal-structure analysis, but H2O is lost under vacuum in the electron microprobe.The crystal structure of ianbruceite was solved by direct methods and refined to an R1 index of 8.6%. The As is tetrahedrally coordinated by four O anions with a mean As–O distance of 1.687 Å. Zigzag [[5]Zn[6]Znφ7] chains extend in the c direction and are linked in the b direction by sharing corners with (AsO4) tetrahedra to form slabs with a composition [Zn2(OH)(H2O)(AsO4)]. The space between these slabs is filled with disordered (H2O) groups and minor lone-pair stereoactive As3+. The ideal formula derived from chemical analysis and crystal-structure solution and refinement is [Zn2(OH)(H2O)(AsO4)](H2O)2.

Description: Davidlloydite, ideally Zn3(AsO4)2(H2O)4, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as elongated prisms (~10:1 length-to-width ratio) that are flattened on {010}, and up to 100 × 20 × 10 µm in size. The crystals occur as aggregates (up to 500 µm across) of subparallel to slightly diverging prisms lying partly on and partly embedded in fine-grained calcioandyrobertsite. Crystals are prismatic along [001] and flattened on {010}, and show the forms {010} dominant and {100} subsidiary. Davidlloydite is colourless with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is distinct on {010}, and no parting or twinning was observed. The Mohs hardness is 3–4. Davidlloydite is brittle with an irregular to hackly fracture. The calculated density is 3.661 g cm -3. Optical properties were measured with a Bloss spindle stage for the wavelength 590 nm using a gel filter. The indices of refraction are a = 1.671, ß = 1.687, ? = 1.695, all ±0.002; the calculated birefringence is 0.024; 2Vobs = 65.4(6)°, 2Vcalc = 70°; the dispersion is r 〈 v, weak; pleochroism was not observed. Davidlloydite is triclinic, space group P1I, with a = 5.9756(4), b = 7.6002(5), c = 5.4471(4) Å, a = 84.2892(9), ß = 90.4920(9), ? = 87.9958(9)°, V = 245.99(5) Å3, Z = 1 and a:b:c = 0.7861:1:0.7167. The seven strongest lines in the X-ray powder diffraction pattern [listed as d (Å), I, (hkl)] are as follows: 4.620, 100, (011, 1I10); 7.526, 71, (010); 2.974, 49, (200, 022I); 3.253, 40, (021, 120); 2.701, 39, (2I10, 002, 1I2I1); 5.409, 37, (001); 2.810, 37, (210). Chemical analysis by electron microprobe gave As2O5 43.03, ZnO 37.95, CuO 5.65, H2O(calc) 13.27, sum 99.90 wt.%. The H2O content and the valence state of As were determined by crystal structure analysis. On the basis of 12 anions with H2O = 4 a.p.f.u., the empirical formula is (Zn2.53Cu0.39)S2.92As2.03O8(H2O)4.The crystal structure of davidlloydite was solved by direct methods and refined to an R1 index of 1.51% based on 1422 unique observed reflections collected on a three-circle rotating-anode (MoKa radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of davidlloydite, sheets of corner-sharing (As5+O4) and (ZnO4) tetrahedra are linked by ZnO2(H2O)4 octahedra. The structure is related to that of parahopeite.

Description: 〈p〉The margins to evolving orogenic belts experience near layer-parallel contraction that can evolve into fold–thrust belts. Developing cross-section-scale understanding of these systems necessitates structural interpretation. However, over the past several decades a false distinction has arisen between some forms of so-called fault-related folding and buckle folding. We investigate the origins of this confusion and seek to develop unified approaches for interpreting fold–thrust belts that incorporate deformation arising both from the amplification of buckling instabilities and from localized shear failures (thrust faults). Discussions are illustrated using short case studies from the Bolivian Subandean chain (Incahuasi anticline), the Canadian Cordillera (Livingstone anticlinorium) and Subalpine chains of France and Switzerland. Only fault–bend folding is purely fault-related and other forms, such as fault-propagation and detachment folds, all involve components of buckling. Better integration of understanding of buckling processes, the geometries and structural evolutions that they generate may help to understand how deformation is distributed within fold–thrust belts. It may also reduce the current biases engendered by adopting a narrow range of idealized geometries when constructing cross-sections and evaluating structural evolution in these systems.〈/p〉

Description: 〈p〉Where primary porosity and permeability of a rock are unfavourable for hydrocarbon production, fractures can improve reservoir potential by enhancing permeability. Higher fracture intensity may create a better-connected fracture network, improving fractured-reservoir quality. Investigations into the controls on fracture intensity commonly conclude that either structural or lithological factors have the greatest influence on fracture abundance. We use the Swift Reservoir Anticline in northwestern Montana to investigate how fracture intensity varies throughout the structure and determine that although structural factors do influence fracture intensity, lithology is the main control at outcrop.〈/p〉 〈p〉The Swift Reservoir Anticline exposes bedding surfaces of the Mississippian Castle Reef Formation dolomite. Field data indicates that fracture intensity is highest in the fold forelimb, decreasing into the backlimb except in outcrops of coarse dolomite where fracture intensity is low, regardless of structural position. Field fracture intensity correlates with whole-rock quartz, kaolinite and porosity percentages. We suggest porosity and composition influence bulk-rock mechanical properties, which, in turn, control the fracture intensity at outcrop. Fracture intensity has a stronger relationship with lithological than structural factors, therefore we suggest that the key to predicting fracture intensity in the subsurface here is understanding how lithology varies spatially.〈/p〉

Description: Ferrochiavennite is a new beryllium silicate zeolite with chemical composition close to Ca 1–2 FeSi 5 Be 2 O 13 (OH) 2 ·2H 2 O. It is described from two syenite pegmatite localities in Norway: Blåfjell, Langangen, Telemark, and the AS Granit larvikite quarry, Tvedalen, Vestfold. The mineral is monoclinic, P 2 1 / c , with a 8.759(5), b 4.864(2), c 31.258(6) Å, β 90.31(6)°, V 1331.7(6) Å 3 , and Z = 4. The crystal structure was refined to R 1 = 0.048 for 3651 observed reflections. The zeolite structure is isostructural with chiavennite, consisting of intersecting channels of nine-, six-, five-, and four-fold rings. The strongest eight reflections of the X-ray powder-diffraction pattern [ d (obs.) in Å ( I ) ( hkl )] are: 15.555 (100) (002), 4.104 (29) (12, 112), 3.938 (36) (13, 113), 3.909 (60) (008), 3.820 (30) (04, 204), 3.251 (66) (017, 210, 11), 3.186 (27) (12, 212), 2.884 (64) (15, 215). The mineral is biaxial (+) with refractive indices α 1.583(1), β 1.589(1), 1.602(1), measured at 590 nm. 2 V (meas.) = 62(4)° from extinction curves 2 V = 76(5)°; 2 V (calc.) = 69°. The optical orientation is X ~ a , Y ~ c , and Z ~ b . The Mohs hardness is ~ 3; D (meas.) = 2.67(2) and D (calc.) = 2.709 g/cm 3 .

Description: Zoned crystals of carbocernaite occur in hydrothermally reworked burbankite-fluorapatite-bearing calcite carbonatite at Bear Lodge, Wyoming. The mineral is paragenetically associated with pyrite, strontianite, barite, ancylite-(Ce), and late-stage calcite, and is interpreted to have precipitated from sulfate-bearing fluids derived from an external source and enriched in Na, Ca, Sr, Ba, and rare-earth elements (REE) through dissolution of the primary calcite and burbankite. The crystals of carbocernaite show a complex juxtaposition of core-rim, sectoral, and oscillatory zoning patterns arising from significant variations in the content of all major cations, which can be expressed by the empirical formula (Ca 0.43–0.91 Sr 0.40–0.69 REE 0.18–0.59 Na 0.18–0.53 Ba 0–0.08 ) 1.96–2.00 (CO 3 ) 2 . Interelement correlations indicate that the examined crystals can be viewed as a solid solution between two hypothetical end-members, CaSr(CO 3 ) 2 and NaREE(CO 3 ) 2 , with the most Na-REE-rich areas in pyramidal (morphologically speaking) growth sectors representing a probable new mineral species. Although the Bear Lodge carbocernaite is consistently enriched in light REE relative to heavy REE and Y (chondrite-normalized La/Er = 500–4200), the pyramidal sectors exhibit a greater degree of fractionation between these two groups of elements relative to their associated prismatic sectors. A sample approaching the solid-solution midline [(Ca 0.57 Na 0.42 ) 0.99 (Sr 0.50 REE 0.47 Ba 0.01 ) 0.98 (CO 3 ) 2 ] was studied by single-crystal X-ray diffraction and shown to have a monoclinic symmetry [space group P 11 m , a = 6.434(4), b = 7.266(5), c = 5.220(3) Å, = 89.979(17)°, Z = 2] as opposed to the orthorhombic symmetry (space group Pb 2 1 m ) proposed in earlier studies. The symmetry reduction is due to partial cation order in sevenfold-coordinated sites occupied predominantly by Ca and Na, and in tenfold-coordinated sites hosting Sr, REE, and Ba. The ordering also causes splitting of carbonate vibrational modes at 690–740 and 1080–1100 cm –1 in Raman spectra. Using Raman micro-spectroscopy, carbocernaite can be readily distinguished from burbankite- and ancylite-group carbonates characterized by similar energy-dispersive spectra.