Elizabeth A. Moffatt

Feinglosite, a new mineral related to brackebuschite, from Tsumeb, Namibia

Abstract Feinglosite, the zinc analogue of arsenbrackebuschite, was found lining a cavity in a sample of massive chalcocite from Tsumeb, Namibia. In this cavity it is associated with wulfenite, anglesite and goethite. The mean of seven electron-microprobe analyses (wt.%) is: PbO 61.4, ZnO 7.3, FeO 1.8, As2O5 22.1, SO3 5.3, H2O (by difference) [2.1], total = [100.00]%, leading to the ideal formula: Pb2(Zn,Fe)[(As,S)O4]·H2O. Feinglosite is monoclinic, space group P21 or P21/m, a 8.973(6), b 5.955(3), c 7.766(6) Å, β 112.20(6)°, with Z = 2. The strongest five reflections of the X-ray powder diffraction pattern are [d in Å (I) (hkl)]: 4.85 (50) (110), 3.246 (100) (112), 2.988 (60) (301), 2.769 (60) (300/211), 2.107 (50) (321). The mineral is pale olive-green, transparent, sectile, and has a white streak and adamantine lustre. It overgrows clusters of goethite crystals and forms globular microcrystalline aggregates up to 0.5-0.75mm in size. The hardness on Mohs‘ scale is 4-5: the mean micro-indentation hardness is 263 at VHN100. Its calculated density is 6.52 g cm−3. The mineral is pale brownish grey in reflected light (when compared with goethite). Visible spectrum reflectance data are presented. Feinglosite is named for Mark N. Feinglos who first recognised the mineral on a specimen in his collection.

An investigation into the cause of corrosion on indoor bronze sculpture

Abstract Corrosion noted on a number of nineteenth and twentieth century indoor bronze sculptures in the collection of the National Gallery of Canada was the cause for a major condition survey of its Canadian, American, and European bronzes. The results led to a comprehensive study, which included material analysis. This article outlines the steps undertaken to determine the extent and type of corrosion, its possible cause(s), and potential remediation. The survey included 136 bronzes, of which 40 were selected for an in-depth study. Indoor air quality tests of the current building, housing the collection since 1988, were carried out. The dossiers and database records of the selected sculptures were reviewed to investigate their condition, treatment, and storage history. The metal, patina, and corrosion products were subjected to analysis. More areas of corrosion were generally associated with predominantly green patinas and chloride-containing compounds identified in either patina or corrosion samples. The most frequently identified compounds in the patina samples were atacamite, a copper(II) chloride hydroxide, and cuprite, a copper(I) oxide. The most frequently identified compounds in the corrosion samples were atacamite and rouaite, a copper(II) hydroxide nitrate. The analysis determined that the current environment is not contributing to the surface alterations of the sculptures; however, past storage conditions, chemical residues from artificial patination, and likely casting residues are the main causes of the current condition.

Conservation Issues in Several Twentieth-Century Canadian Oil Paintings: The Role of Zinc Carboxylate Reaction Products

In an on-going study of the materials and techniques of twentieth-century Canadian painters, similar conservation issues in oil paintings by various artists have been noted. These include delamination and lifting paint, zinc soap protrusions and surface efflorescence or accretions. Examples of these phenomena are presented. Delamination in an oil painting from 1956 was found to be related to an underlayer with a high concentration of zinc fatty acid salts (zinc soaps). In two paintings that date from 1936 and 1937, zinc soaps have aggregated and formed protrusions that have broken through the paint surface. The protrusions were analysed using a combination of SEM-EDX, GCMS and FTIR. The FTIR spectra were compared to those of synthetic zinc palmitate, stearate, azelate and oleate. The combined GCMS and FTIR results indicate that the protrusions contain primarily zinc palmitate and stearate. Peak splitting in the FTIR spectrum, which is not observed in synthetic zinc palmitate, stearate or binary palmitate-stearate salts, is likely due to structural distortion. The final example describes a disfiguring surface accretion on a 1952–1954 painting caused by the reaction of zinc with a low molecular weight carboxylic acid (2-hydroxypropanoic or lactic acid).

Steverustite, (OH)5[Cu+(S6+O3S2-)3](H2O)2, a new thiosulphate mineral from the Frongoch Mine Dump, Devils Bridge, Ceredigion, Wales: description and crystal structure

Abstract Steverustite, ideally Pb52+(OH)5[Cu+(S6+O3S2-)3](H2O)2, is a new supergene mineral from the Frongoch mine dump, Devils Bridge, Ceredigion, Wales. It generally forms fibrous fan-like bundles that occur in small cavities in quartz veins with other supergene species. Crystals are fibrous to acicular, elongated along [010], and are bounded by (h0l) faces too small to index reliably. It is transparent, colourless to white with a white streak, has a vitreous lustre, does not fluoresce under ultraviolet light and is brittle with a splintery fracture. The calculated density is 5.150 g/cm3, and the calculated mean refractive index is 1.94. The mineral is monoclinic, P21/n, a 12.5631(7), b 8.8963(5), c 18.0132(11) Å, β 96.459(1)º, V 2000.5(3) Å3, Z = 4, a:b:c = 1.41217:1:2.02480. The seven strongest lines in the X-ray powder diffraction pattern are as follows: d (Å), I, (h k l): 3.934, 10, (1̄14); 3.934, 8, (1̄11); 3.348, 7, (3̄13); 6.211, 6, (200); 4.797, 6, (211); 3.026, 6, (3̄14); 2.837, 5, (016). Chemical analysis by electron microprobe gave PbO 72.59, SO3 15.78, Cu2O 4.47, S2- 6.32, H2O 4.83, O=S2- -3.15, total 100.84 wt.% where the amount of H2O was determined by crystal-structure analysis. The resulting empirical formula is Pb4.992+Cu0.96+(S6+O3S2-)3.03(OH)4.88(H2O)1.67, based on O + OH + H2O + S2- = 18.67 a.p.f.u. (atoms per formula unit) with H2O = 1.67 a.p.f.u. (from crystal-structure solution and refinement). The crystal structure of steverustite was solved by direct methods and refined to R1 = 2.7% for 3366 unique (Fo > 4σF) reflections. There are five distinct Pb2+ cations with coordination numbers from [8] to [11], all of which show stereoactive lone-pair behaviour and which form a strongly bonded cluster of composition [Pb5(OH)5]. There is one Cu+ cation triangularly coordinated by three S2- atoms that belong to three thiosulphate groups, forming a Cu+(S6+O3S2-)3 group. The [Pb5(OH)5] units and [Cu(S2O3)3] groups occur at the vertices of interpenetrating 36 nets to form layers of composition [Pb5(OH)5Cu(S2O3)3] parallel to (010) which are linked by weaker bonds. Examination of the stereochemistry of thiosulphate and thionate structures shows that the combination of and S-S distances are distinct for these two types of structures.

Juabite, Cu 5 (Te (super 6+) O 4 ) 2 (As (super 5+) O 4 ) 2 .3H 2 O, a new mineral species from the Centennial Eureka Mine, Juab County, Utah

Abstract Juabite, ideally Cus(Te6+O4)2(AsS5+O4)2·3H20, is triclinic, space-group choices Pl(1) or P1̅(2), with unit-cell parameters refined from powder data: a = 8.984(5), b = 10.079(7), c = 8.975(5) Å,α = 102.68(7) °, β = 92.45(6)° , γ = 70.45(5) ° V = 746.8(8) Å, a:b:c =o 0.8914:1:0.8905, Z = 2. The strongest seven reflections of the X-raypowder-diffraction pattern [d in Å (i)(hkl)] are: 9.28 (70)(010), 4.65−(70)(020), 3.097 (100)(030,2̅11), 3.018 (60)(212), 2.658 (50)(3̅01), 2.468 (50)(2̅22̅) and 1.740 (50)(1̅15̅, 521, 1̅51̅). The mineral is an extremely rare constituent on the dumps of the Centennial Eureka mine, Juab County, Utah, U.S.A., where it occurs as crystalline platy masses that average 0.2−0.3 mm in longest dimension within small interconnected vugs of drusy quartz. Associated minerals are enargite, beudantite, and an undefined, possible Pb-analogue of arsenobismite. Individual crystals are subhedral to euhedral and average 125 × 100 × 1−2 μm in size. Cleavage {010} perfect. Forms are: {010} major; {100}, {1̅01}, and {101} minor. The mineral is translucent (masses) to transparent (crystals), emerald-green, with a pale green streak, and an uneven to subconchoidal fracture. Juabite is vitreous to adamantine (almost gemmy) on cleavage faces, brittle, and nonfluorescent; H (Mohs) 3−4; D (calc.) 4.59 g/cm3 for the idealised formula. In polished section, juabite is white in plane-polarised reflected light in air with ubiquitous turquoise-blue internal reflections; bireflectance and anisotropy are unknown (due to interference from internal reflections). Averaged electronmicroprobe analyses yielded CuO 38.25, PbO 0.57, TeO3 32.58, As205 22.81, H20 (calc. assuming 3H20) [5.19], total [99.40] wt.%, leading to the empirical formula (Cu5.01Pb0.03)∑5.04(TeO4)1.93 (AsO4)2.07·3.00H2O based on O = 19. The infrared absorption spectrum shows definite bands for structural H20 with an O-H stretching frequency centred at 3283 cm−1 and a H-O-H flexing frequency centred at 1642 cm−1. The mineral name is for the county within the state of Utah in which the Centennial Eureka mine is located.

Leisingite, Cu(Mg,Cu,Fe,Zn) 2 Te (super 6+) O 6 .6H 2 O, a new mineral species from the Centennial Eureka Mine, Juab County, Utah

Abstract Leisingite, ideally Cu(Mg,Cu,Fe,Zn)2Te6+O6·6H2O, is hexagonal, P3 (143), with unit-cell parameters refined from powder data: a = 5.305(1), c = 9.693(6) Å, V = 236.2(2) Å3, c/a = 1.8271, Z = 1. The strongest six reflections of the X-ray powder-diffraction pattern [d in Å (I) (hkl)] are: 9.70 (100) (001), 4.834 (80) (002), 4.604 (60) (100), 2.655 (60) (110), 2.556 (70) (111) and 2.326 (70) (112). The mineral is found on the dumps of the Centennial Eureka mine, Juab County, Utah, U.S.A. where it occurs as isolated, or rarely as clusters of, hexagonal-shaped very thin plates or foliated masses in small vugs of crumbly to drusy white to colourless quartz. Associated minerals are jensenite, cesbronite and hematite. Individual crystals are subhedral to euhedral and average less than 0.1 mm in size. Cleavage {001} perfect. Forms are: {001} major; {100}, {110} minute. The mineral is transparent to somewhat translucent, pale yellow to pale orange-yellow, with a pale yellow streak and an uneven fracture. Leisingite is vitreous with a somewhat satiny to frosted appearance, brittle to somewhat flexible and nonfluorescent; H(Mohs) 3-4; D(calc.) 3.41 for the idealized formula; uniaxial negative, ω = 1.803(3), ɛ = 1.581 (calc.). Averaged electron-microprobe analyses yielded CuO 24.71, FeO 6.86, MgO 6.19, ZnO 0.45, TeO3 36.94, H2O (calc.) [21.55], total [96.70] wt.%, leading to the empirical formula Cu1.00(Mg0.77Cu0.56Fe0.48Zn0.03)Σ1.84Te1.066+O6.02·5.98H2O based on O = 12. The infrared absorption spectrum shows definite bands for structural H2O with an O-H stretching frequency centered at 3253 cm−1 and a H-O-H flexing frequency centered at 1670 cm−1. The mineral name honours Joseph F. Leising, Reno, Nevada, who helped collect the discovery specimens.

Carlosbarbosaite, ideally (UO2)2Nb2O6(OH)2·2H2O, a new hydrated uranyl niobate mineral with tunnels from Jaguaraçu, Minas Gerais, Brazil: description and crystal structure

Abstract Carlosbarbosaite, ideally (UO2)2Nb2O6(OH)2 ·2H2O, is a new mineral which occurs as a late cavity filling in albite in the Jaguaraçu pegmatite, Jaguaraçu municipality, Minas Gerais, Brazil. The name honours Carlos do Prado Barbosa (1917-2003). Carlosbarbosaite forms long flattened lath-like crystals with a very simple orthorhombic morphology. The crystals are elongated along [001] and flattened on (100); they are up to 120 μm long and 2-5 μm thick. The colour is cream to pale yellow, the streak yellowish white and the lustre vitreous. The mineral is transparent (as individual crystals) to translucent (massive). It is not fluorescent under either long-wave or short-wave ultraviolet radiation. Carlosbarbosaite is biaxial(+) with α = 1.760(5), β = 1.775(5), γ = 1.795(5), 2Vmeas. = 70(1)°, 2Vcalc. = 83°. The orientation is X ∥ a, Y ∥ b, Z ∥ c. Pleochroism is weak, in yellowish green shades, which are most intense in the Z direction. Two samples were analysed. For sample 1, the composition is: UO3 54.52, CaO 2.07, Ce2O3 0.33, Nd2O3 0.49, Nb2O5 14.11, Ta2O5 15.25, TiO2 2.20, SiO2 2.14, Fe2O3 1.08, Al2O3 0.73, H2O (calc.) 11.49, total 104.41 wt.%; the empirical formula is (⃞0.68Ca0.28Nd0.02Ce0.02)∑=1.00[U1.44⃞0.56O2.88(H2O)1.12](Nb0.80Ta0.52Si0.27Ti0.21Al0.11Fe0.10)∑=2.01O4.72(OH)3.20(H2O)2.08. For sample 2, the composition is: UO3 41.83, CaO 2.10, Ce2O3 0.31, Nd2O3 1.12, Nb2O5 14.64, Ta2O5 16.34, TiO2 0.95, SiO2 3.55, Fe2O3 0.89, Al2O3 0.71, H2O (calc.) 14.99, total 97.43 wt.%; the empirical formula is (⃞0.67Ca0.27Nd0.05Ce0.01)∑=1.00[U1.04⃞0.96O2.08(H2O)1.92] (Nb0.79Ta0.53Si0.42Ti0.08Al0.10Fe0.08)∑=2.00O4.00(OH)3.96(H2O)2.04. The ideal endmember formula is (UO2)2Nb2O6(OH)2 ·2H2O. Calculated densities are 4.713 g cm-3 (sample 1) and 4.172 g cm-3 (sample 2). Infrared spectra show that both (OH) and H2O are present. The strongest eight X-ray powder- diffraction lines [listed as d in Å(I)(hkl)] are: 8.405(8)(110), 7.081(10)(200), 4.201(9)(220), 3.333(6)(202), 3.053(8)(022), 2.931(7)(420), 2.803(6)(222) and 2.589(5)(040,402). The crystal structure was solved using single-crystal X-ray diffraction (R = 0.037) which gave the following data: orthorhombic, Cmcm, a = 14.150(6), b = 10.395(4), c = 7.529(3) Å, V = 1107(1) Å3, Z= 4. The crystal structure contains a single U site with an appreciable deficiency in electron scattering, which is populated by U atoms and vacancies. The U site is surrounded by seven O atoms in a pentagonal bipyramidal arrangement. The Nb site is coordinated by four O atoms and two OH groups in an octahedral arrangement. The half-occupied tunnel Ca site is coordinated by four O atoms and four H2O groups. Octahedrally coordinated Nb polyhedra share edges and corners to form Nb2O6(OH)2 double chains, and edge-sharing pentagonal bipyramidal U polyhedra form UO5 chains. The Nb2O6(OH)2 and UO5 chains share edges to form an open U-Nb-φ framework with tunnels along [001] that contain Ca(H2O)4 clusters. Carlosbarbosaite is closely related to a family of synthetic U-Nb-O framework tunnel structures, it differs in that is has an (OH)-bearing framework and Ca(H2O)4 tunnel occupant. The structure of carlosbarbosaite resembles that of holfertite.

A Materials Investigation into the Metal Composition and Coating Structures of Four Ming Dynasty Cast Iron Statues, with Subsequent Discussion and Development of a Treatment Protocol

Four iron statues dated by inscription to the Ming Dynasty, China, (1491 A.D.) were investigated for their metal composition and coating structures. The investigation was initiated with the intent of ascertaining whether any prior treatment had been done and to determine the present condition of the object. During visual examination and simple surface cleaning, it became apparent that the objects had some form of surface decoration and polychrome. On closer examination, gilding, lacquer, and traces of pigment around the hat, eyes, and garment were visible. A sample of the metal was taken for metallography and chemical compositional analysis. Samples were taken from the surface of the four objects to identify the composition of the observed decoration and corrosion. The results revealed that the statues are white cast iron and were fully decorated with multiple colours and gilding as well as being sequentially lacquered. Recommendations for the cleaning and conservation of these objects are given.