Glenn Poirier

Joëlbruggerite, Pb3Zn3(Sb5+,Te6+)As2O13(OH,O), the Sb5+ analog of dugganite, from the Black Pine mine, Montana

Abstract Joëlbruggerite, ideally Pb3Zn3(Sb5+,Te6+)As2O13(OH,O), is a new arsenate mineral (IMA 2008-034) and the Sb5+ analog of dugganite, from the Black Pine mine, 14.5 km northwest of Philipsburg, Granite County, Montana. It is usually found perched on mimetite; other species that may be present include malachite, azurite, pseudomalachite, chalcocite, beudantite-corkite, duftite, dugganite, and kuksite, in milky quartz veins. Joëlbruggerite occurs as barrel-shaped or prismatic crystals up to about 50 μm across in various shades of purple. The crystals have an adamantine luster and a white streak. Mohs hardness is about 3. The fracture is irregular, and the tenacity is brittle. Joëlbruggerite crystals are uniaxial (-), with a calculated refractive index of n = 1.993, and weakly pleochroic: X = Y = gray, Z = purple; absorption: Z > X = Y. Crystals show straight extinction and are length-fast. The empirical chemical formula (mean of 5 electron microprobe analyses) calculated on the basis of 14 [O + OH] anions is Pb3.112(Zn2.689Fe2+0.185)Σ2.874(Sb5+0.650Te6+0.451)Σ1.101(As1.551P0.203Si0.160)Σ1.914O13.335(OH)0.665. Joëlbruggerite is trigonal, space group P321, a = 8.4803(17), c = 5.2334(12) Å, V = 325.94(12) Å3, Z = 1. The five strongest lines in the powder X-ray diffraction pattern are [dobs in Å (I) (hkl)]: 3.298 (100) (111), 3.008 (89) (021), 1.905 (39) (122, 131), 2.456 (36) (012, 121, 030), and 1.609 (30) (112, 132, 231, 140). The crystal structure was solved from single-crystal X-ray diffraction data and refined to R1 = 0.038 on the basis of 604 unique reflections with F > 4σ(F). It is composed of heteropolyhedral sheets of edge-sharing (Sb,Te)O6 octahedra and PbO8 disphenoids, oriented parallel to (001). The sheets are cross-linked by AsO4 and ZnO4 tetrahedra, which share corners to form an interlinked, two- and threeconnected two-dimensional net parallel to (001). The mineral is named for Joël Brugger (born 1967), Swiss-Australian mineralogist, for his contributions to mineralogy.

Naldrettite, Pd2Sb, a new intermetallic mineral from the Mesamax Northwest deposit, Ungava region, Québec, Canada

Abstract Naldrettite, Pd2Sb, is a new intermetallic mineral discovered in the Mesamax Northwest deposit, Cape Smith fold belt, Ungava region, northern Québec. It is associated with monoclinic pyrrhotite, pentlandite, chalcopyrite, galena, sphalerite, cobaltite, clinochlore, magnetite, sudburyite (PdSb), electrum and altaite. Other rarer associated minerals include a second new mineral (ungavaite, Pd4Sb3), sperrylite (PtAs2), michenerite (PdBiTe), petzite (Ag3AuTe4) and hessite (Ag2Te). Naldrettite occurs as anhedral grains, which are commonly attached or moulded to sulphide minerals, and also associated with clinochlore. Grains of naldrettite vary in size (equivalent circle diameter) from ~10 to 239 μm, with an average of 74.4 μm (n = 632). Cleavage was not observed and fracture is irregular. The mineral has a mean micro-indentation hardness of 393 kg/mm2. It is distinctly anisotropic, non- pleochroic, has weak bireflectance, and does not exhibit discernible internal reflections. Some grains display evidence of strain-induced polysynthetic twinning. Naldrettite appears bright creamy white in association with pentlandite, pyrrhotite, clinochlore and chalcopyrite. Reflectance values in air (and in oil) for R1 and R2 are: 49.0, 50.9 (35.9, 37.6) at 470 nm, 53.2, 55.1 (40.3, 42.1) at 546 nm, 55.4, 57.5 (42.5, 44.3) at 589 nm and 58.5, 60.1 (45.4, 47.2) at 650 nm. The average of 69 electron-microprobe analyses on 19 particles gives: Pd 63.49, Fe 0.11, Sb 35.75, As 0.31, and S 0.02, total 99.68 wt.%, corresponding to (Pd1.995Fe0.007)2.002(Sb0.982As0.014S0.002)0.998. The mineral is orthorhombic, space group Cmc21, a 3.3906(1), b 17.5551(5), c 6.957(2) Å , V 414.097(3) Å3, Z = 8. Dcalc is 10.694(1) g/cm3. The six strongest lines in the X-ray powder-diffraction pattern [d in Å (I)(hkl)] are: 2.2454(100)(132), 2.0567(52)(043), 2.0009(40)(152), 1.2842(42)(115), 1.2122(50)(204) and 0.8584(56)(1.17.4).

The mechanism of charge compensation in Cu-Fe-PGE thiospinels from the Penikat layered intrusion, Finland

Abstract Thiospinels of Cu-(Fe) and platinum-group elements (PGE) are relatively abundant in the Kirakkajuppiua PGE deposit of the Peuikat layered complex. Finland. In actinolite-clinochlore rock that is nearly base-metal sulfide-free and relatively poor in chromite, the thiospinels occur as subhedral or anhedral grains (up to 0.4 mm). They are members of the cuprorhodsite-ferrorhodsite and cuprorhodsite-malanite series, relatively poor in cuproiridsite. and display considerable grain-to- grain variations in Cu. Fe. Pt. and Rh. Strong negative Fe-Cu. Pt(+Ir)-Fe. Rh-Cu. and Rh-Pt and strong positive Pt(+Ir)-Cu and Rh-Fe correlations in these thiospinels are indicative of a coupled substitution: Fe-for-Cu substitution in the tetrahedral (A) sites causes an excess in formal positive charge, which is compensated by Rh-for-(Pt+Ir) substitution hi the octahedral (B) sites. Probable valence states in the Fe-free and Fe-rich end-members of the solid-solution series at Penikat are Cu+[Rli3+(Pt,Ir)4+] S4- and (FefoCu0.5+)Rh2S42-. and these suggest the heterovalent substitution scheme AFe3+ + 2 BRh3+ → ACu+ + 2 BPt4+(+2 Ir4+) to incorporate Fe in the ferrorhodsite-rich end member.

Characterization of ferric arsenate-sulfate compounds: Implications for arsenic control in refractory gold processing residues

Abstract A combination of techniques, including powder X-ray diffraction (XRD), electron microprobe analysis (EPMA), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAFS), is used to characterize the common ferric-arsenate-sulfate compounds, which could result from the pressure oxidation of refractory gold ores at elevated temperatures. Three general types of precipitate are identified; namely, arsenate-bearing basic ferric sulfate [FeSO4(OH) and designated as BFS], ferric arsenate-sulfate [an extensive solid solution Fe(AsO4)0.2-0.7(SO4)0.7-0.2(OH)0.7-0.2 and designated as FAS], and hydrated ferric orthoarsenate (FeAsO4·0.75H2O). The crystal structure of FAS is solved by precession electron-diffraction experiments. The structures of BFS and FAS are constructed from octahedral Fe3+ chains, which are cross-linked by sulfate and arsenate tetrahedra. Extensive substitution of arsenate for sulfate occurs in both types of compounds with charge neutrality being maintained by variations in the (OH) content. The XAFS spectra indicate that the local structures of both BFS and FAS are made of corner-linked single chains of FeO6 octahedra where the chains are linked by AsO4 or SO4 tetrahedra forming alternating layers of FeO6 octahedra and AsO4 or SO4 tetrahedra. Preliminary toxicity characteristics leaching procedure (TCLP) testing of the precipitates indicates that FAS with a molar ratio As/(As+S) ratio of ≤0.5 could be an acceptable material for disposal in a tailings impoundment, whereas more As-rich FAS and BFS may require further treatment. The results for the laboratory-prepared precipitates are compared with those obtained on three residues from the processing of refractory gold ores. The major As-carrier in one of the residues is FAS, whereas As-bearing goethite and hematite are the dominant As-carriers in the other two residues. Thus, the mineralogical characteristics of the residues dictate the appropriate arsenic management and disposal options in the processing of refractory gold ores.

Tatyanaite, a new platinum-group mineral, the Pt analogue of taimyrite, from the Noril'sk complex (northern Siberia, Russia)

Tatyanaite, a new mineral from Noril9sk (Siberia), is the Pt analogue of taimyrite. It is defined as the member(s) of the tatyanaite-taimyrite solid-solution series with Pt > Pd. Tatyanaite solid solution occurs in massive sulphide ore, which consists of chalcopyrite and subordinate pentlandite, pyrrhotite, and cubanite (or isocubanite). It occurs as central zones of large, elongate grains (up to ∼1 mm) and as aggregates of smaller grains associated with Ag-Au alloys. The associated minerals include unusually Pt-rich taimyrite [(Pd 1.25 Pt 0.86 )(Cu 0.85 Ni ) (Sn 1.01 Sb 0.02 )], atokite-rustenburgite, paolovite, froodite, sperrylite, maslovite, and galena. Cryptic zoning (Pt increases and Pd decreases toward the centre) and polysynthetic twins are characteristic. In reflected light, tatyanaite is pink with lilac tinge in air. Bireflectance is weak to distinct, from brownish pink to pinkish lilac. Anisotropy is distinct to moderate, from light brown to dark blue. Reflectance percentages in air and (in oil) are, for R 1 and R 2 , 470 nm 42.8, 44.1 (32.8, 33.3), 546 nm 49.5, 50.0 (37.6, 38.8), 589 nm 51.8, 54.6 (38.9, 39.9), and 650 nm 55.6, 56.8 (41.6, 44.2). It is ductile; the microhardness is VHN 20 = 292-348, mean of 327 kg/mm 2 . The average of nine electron-microprobe analyses gave Pt 45.38, Pd 19.53, Cu 10.62, Ni 0.15, Fe 0.03, Sn 23.02, Sb 0.27, sum 99.0 wt.%, corresponding to [(Pt 4.76 Pd 3.75 ) ∑8.51 Cu 0.48 ] ∑8.99 (Cu 2.94 Ni 0.05 Fe 0.01 ) ∑3.00 (Sn 3.96 Sb 0.05 ) ∑4.01 [or to (Pt 1.19 Pd 0.94 )(Cu 0.85 Ni 0.01 Fe ) (Sn 0.99 Sb 0.01 )]. The powder pattern is similar to that of synthetic Pd 9 Cu 3 Sn 4 , and, by analogy with the latter, it was indexed for an orthorhombic cell with a = 7.89(1) A, b = 4.07(1) A and c = 7.73(1) A, and V = 248(1) A 3 . The three strongest lines in the pattern are 2.283 (10, 212), 2.163 (4, 203) and 1.369 (3, 323). Tatyanaite-taimyrite formed from a late-stage liquid rich in noble metals, Cu and Sn.

Hydroniumpharmacosiderite, a new member of the pharmacosiderite supergroup from Cornwall, UK: structure and description

Abstract Hydroniumpharmacosiderite, ideally (H3O)Fe4(AsO4)3(OH)4·4H2O, is a new mineral from Cornwall, UK, probably from the St. Day group of mines. It occurs as a single yellowish green, slightly elongated cube, measuring 0.17 mm × 0.14 mm × 0.14 mm. The mineral is transparent with a vitreous lustre. It is brittle with a cleavage on {001}, has an irregular fracture, a white streak and a Mohs hardness of 2-3 (determined on H3O-exchanged pharmacosiderite). Hydroniumpharmacosiderite has a calculated density of 2.559 g cm-3 for the empirical formula. The empirical formula, based upon 20.5 oxygen atoms, is: [(H3O)0.50K0.48Na0.06]1.04(Fe3.79Al0.22)4.01[(As2.73P0.15)2.88O12](OH)4·4H2.14O. The five strongest lines in the X-ray powder diffraction pattern are [dobs (Å), Iobs, (hkl)]: 8.050,100,(001); 3.265,35,(112); 2.412,30,(113); 2.830,23,(202); 4.628,22,(111). Hydroniumpharmacosiderite is cubic, space group P4̄3m with a = 7.9587(2) Å, V = 504.11(2) Å3 and Z = 1. The crystal structure was solved by direct methods and refined to R1 = 0.0481 for 520 reflections with I > 2σ(I). The structure is consistent with determinations for H3O-exhchanged pharmacosiderite and the general pharmacosiderite structure type.

Pb3Fe3+2(PO4)4(H2O), a new octahedral-tetrahedral framework structure with double-strand chains

A new lead iron(III) hydrated phosphate, Pb 3 Fe 2 (PO 4 ) 4 (H 2 O), has been synthesised hydrothermally in Teflon-lined stainless steel autoclaves at 220 °C for 7 days, with an initial pH of 1.5. It is the first example of a synthetic hydrous Pb–Fe 3+ phosphate. Crystals are small, colourless to white prisms, uniaxial (+) and non-pleochroic. The calculated refractive index for white light is n = 1.95. Single-crystal structure determination ( R ( F ) = 0.0457) shows Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) to be tetragonal, space group P 4 1 2 1 2 (no. 92), with a = 9.0440(10), c = 16.766(3) A, V = 1371.4(3) A 3 and Z = 4. Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) has a structure type which is based on a tetrahedral–octahedral framework of FeO 6 octahedra sharing corners with PO 4 tetrahedra, with Pb atoms and H 2 O molecules occupying voids in the framework. Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) is homeotypic with synthetic Pb 3 Cr 2 (PO 4 ) 4 ; both compounds share the same heteropolyhedral topology and the same space group, but only Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) contains an additional position occupied by a water molecule. The octahedral–tetrahedral chain of Pb 3 Fe 2 (PO 4 ) 4 (H 2 O) is topologically similar to double–strand chains found in the structures of hannayite, galliskiite, kapundaite, PbIn(AsO 4 )(AsO 3 OH) and Na 2.88 Fe(PO 4 ) 2 . Infrared spectroscopy is used to describe the vibrational properties of Pb 3 Fe 2 (PO 4 ) 4 (H 2 O).

Sb5+ and Sb3+ substitution in segnitite: A new sink for As and Sb in the environment and implications for acid mine drainage

Abstract A sample of Sb-rich segnitite from the Black Pine mine, Montana, U.S.A., has been studied by microprobe analyses, single-crystal X-ray diffraction, and μ-EXAFS and XANES spectroscopy. Linear combination fitting of the spectroscopic data provided Sb5+:Sb3+ = 85(2):15(2), where Sb5+ is in octahedral coordination substituting for Fe3+ and Sb3+ is in tetrahedral coordination substituting for As5+. Based upon this Sb5+:Sb3+ ratio, the microprobe analyses yielded the empirical formula Pb1.02 H1.02(Fe3+2.36Sb5+0.41Cu2+0.27)Σ3.04(As5+1.78Sb3+0.07S6+0.02)Σ1.88O8(OH)6.00. The crystal structure refinement and bond valence analysis are consistent with these cation site assignments. The formation of Sb-rich segnitite opens new possibilities for Sb sinks within the supergene zone. Segnitite may, in fact, be an ideal host for the sequestering of several toxic elements for pH < 2. At higher pH values, As is more likely to be incorporated into schwertmannite and ferrihydrite.

The mineralogy and crystal chemistry of alkaline pegmatites in the Larvik Plutonic Complex, Oslo rift valley, Norway. Part 1. Magmatic and secondary zircon: implications for petrogenesis from trace-element geochemistry

Abstract A detailed electron microprobe (EMP) and laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) study of zircon from six types of miaskitic and agpaitic alkaline pegmatite from the Larvik Plutonic Complex, Oslo rift valley, Norway, was undertaken to shed light on the pegmatite petrogenesis. Detailed rare earth element (REE) analyses indicate important differences between the zircon from each type of pegmatite. Primary zircon from miaskitic Stavern-, Tvedalen- and Stålaker-type pegmatites has a mean ΣREE = 704 ppm, is depleted in LREE and has a significant positive Ce anomaly (Ce/Ce* = 44-67) and negative Eu anomaly (Eu/Eu* = 0.15-0.18). Secondary Tvedalen-type zircon is REE-enriched (ΣREE = 5035 ppm), with a flatter REE pattern, Ce/Ce* = 0.97 and a Eu anomaly similar to primary Tvedalen-type zircon (Eu/Eu* = 0.21). Secondary zircon from agpaitic Langesundsfjord-type pegmatites display a distinctive flat REE pattern characterized by overall REE enrichment (ΣREE = 967), Ce/Ce* = 1.92, and a minor negative Eu anomaly (Eu/Eu* = 0.37). Zircon from agpaitic Bratthagen-type pegmatites occurs as both altered primary and secondary phases and is strongly enriched in REE relative to other zircon (ΣREE = 4178 and 8388, respectively). Primary Bratthagen-type zircon has a similarREE pattern to miaskitic zircon, with a steeper HREE profile and smaller Ce and Eu anomalies (Eu/Eu* = 0.73; Ce/Ce* = 6.22). Secondary Bratthagen-type zircon is strongly enriched in LREE compared to primary zircon, does not display a positive Ce anomaly and has Eu/Eu* = 0.56. The altered primary and secondary Bratthagen-type zircons have elevated Th/UN ratios, suggesting a different melt source for Bratthagen-type agpaitic pegmatites. Zircon from external pegmatites has trace-element signatures similar to Stavern-, Tvedalen- and Stålaker-type primary zircon with Ce/Ce* = 214 and Nb/Ta and Th/U ratios that are similar to those of secondary Langesundsfjord- and Bratthagen-type zircon. It is suggested that the parental melt of the external pegmatites is the same as the miaskitic pegmatites, but that it has undergone alteration by hydrothermal fluids derived from the host basalt, or by post-magmatic F-rich fluids which mobilize Nb and Th. On the basis of texture, morphology and geochemistry, two populations of zircon can be recognized: (1) primary zircon from miaskitic pegmatites; and (2) secondary zircon from post-magmatic, hydrothermal assemblages. The U-Th-Pb isotope analyses indicate that the secondary and altered zircon are depleted in 238U, and enriched in LREE. Interaction of a post-magmatic hydrothermal fluid with an externally derived meteoric fluid is suggested to have influenced the REE signatures, and in particular the Eu and Ce anomalies of the late-stage zircons.

Palladosilicide, Pd2Si, a new mineral from the Kapalagulu Intrusion, Western Tanzania and the Bushveld Complex, South Africa

Abstract Palladosilicide, Pd2Si, is a new mineral (IMA 2014-080) discovered in chromite-rich samples from the Kapalagulu intrusion, western Tanzania (30°03ʹ51ʺE 5°53ʹ16ʺS and 30°05ʹ37ʺE 5°54ʹ26ʺS) and from the UG-2 chromitite, Bushveld complex, South Africa. A total of 13 grains of palladosilicide, ranging in size from 0.7 to 39.1 μm (equivalent circle diameters), were found. Synthetic Pd2Si is hexagonal, space group P6̅2m, with a = 6.496(5), c = 3.433(4) Å, V = 125.5(1) Å3, c:a = 0.529 with Z = 3. The strongest lines calculated from the powder pattern (Anderko and Schubert, 1953) are [d in Å (I) (hkl)] 2.3658 100 (111); 2.1263 37 (120); 2.1808 34 (021); 3.240 20 (110); 1.8752 19 (030); 1.7265 12 (002); 1.3403 11 (122); 1.2089 10 (231). The calculated density for three analyses varies from 9.562 to 9.753 g cm-3. Palladosilicide is considered to be equivalent to synthetic Pd2Si based on results from electron backscattered diffraction analyses. Reflectance data in air for the four Commission on Ore Mineralogy wavelengths are [λ nm, R1 (%) R2 (%)] 470 49.6 52.7; 546 51.2 53.8; 589 51.6 53.7; 650 51.7 53.3 and the mineral is bright creamy white against chromite, weakly bireflectant and displays no discernible pleochroism or twinning. It is weakly anisotropic, has weak extinction and rotation tints in shades of blue and olive green. Electron probe microanalyses of palladosilicide yield a simplified formula of Pd2Si.