ALBERT

Description: 〈div data-abstract-type="normal"〉〈p〉Pampaloite, AuSbTe, is a new mineral discovered in the Pampalo gold mine, 65 km east of Joensuu, Finland. It forms anhedral grains (up to ~20 μm) intergrown with gold, frohbergite and altaite. Pampaloite is brittle and has a metallic lustre. Values of VHN〈span〉25〈/span〉 lie between 245 and 295 kg/mm〈span〉2〈/span〉, with a mean value of 276 kg/mm〈span〉2〈/span〉, corresponding to a Mohs hardness of ~4–5 (measured on synthetic material). In plane-polarised light, pampaloite is white with medium to strong bireflectance, weak reflectance pleochroism from slightly pinkish brown to slightly bluish white (only visible in grains of synthetic material containing multiple orientations), and strong anisotropy, with blue to light brown rotation tints; it exhibits no internal reflections. Reflectance values of pampaloite in air (〈span〉R〈/span〉〈span〉1,〈/span〉〈span〉R〈/span〉〈span〉2〈/span〉 in %) are: 60.0, 62.5 at 470 nm, 62.5, 64.8 at 546 nm, 63.2, 65.6 at 589 nm and 63.7, 66.0 at 650 nm. Ten electron-microprobe analyses of natural pampaloite give an average composition: Au 44.13, Sb 27.44 and Te 28.74, total 100.31 wt.%, corresponding to the empirical formula Au〈span〉1.00〈/span〉Sb〈span〉1.00〈/span〉Te〈span〉1.00〈/span〉 based on 3 atoms; the average of eleven analyses on synthetic pampaloite is: Au 44.03, Sb 27.26, and Te 29.08, total 100.38 wt.%, corresponding to Au〈span〉0.99〈/span〉Sb〈span〉1.00〈/span〉Te〈span〉1.01〈/span〉. The density, calculated on the basis of the empirical formula, is 9.33 g/cm〈span〉3〈/span〉.The mineral is monoclinic, space group 〈span〉C〈/span〉2/〈span〉c〈/span〉, with 〈span〉a〈/span〉 = 11.947(3), 〈span〉b〈/span〉 = 4.481(1) Å, 〈span〉c〈/span〉 = 12.335(3) Å, β = 105.83(2)°, 〈span〉V〈/span〉 = 635.3(3) Å〈span〉3〈/span〉 and 〈span〉Z〈/span〉 = 8. The crystal structure was solved and refined from the single-crystal X-ray-diffraction data of synthetic AuSbTe. The pampaloite crystal structure can be considered as a monoclinic derivative of the CdI〈span〉2〈/span〉 structure composed of [AuTe〈span〉3〈/span〉Sb〈span〉3〈/span〉] octahedra. The strongest lines in the powder X-ray diffraction pattern of synthetic pampaloite [〈span〉d〈/span〉 in Å (〈span〉I〈/span〉) (〈span〉hkl〈/span〉)] are: 4.846(24)(〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/resource/id/urn:cambridge.org:id:binary:20190709073523038-0660:S0026461X18001299:S0026461X18001299_inline1.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉02), 3.825(18)(111), 2.978(100)(〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/resource/id/urn:cambridge.org:id:binary:20190709073523038-0660:S0026461X18001299:S0026461X18001299_inline2.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉11), 2.968(50)(004), 2.242(25)(020), 2.144(55)(313), 2.063(33)(〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/resource/id/urn:cambridge.org:id:binary:20190709073523038-0660:S0026461X18001299:S0026461X18001299_inline3.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉15) and 1.789(18)(024).〈/p〉〈/div〉

Description: Jacutingaite, Pt2HgSe3, is a new species of platinum-group mineral discovered at the Cauê iron-ore deposit, Itabira district, Minas Gerais, Brazil. Observed in a polished section, the mineral is about 50 μm across and occurs on an aggregate of atheneite, potarite and hematite. The new mineral is partly altered to a Pt–O phase. Synthetic jacutingaite is megascopically grey in color, has a metallic luster and a grey streak. The mineral is brittle, with a very good {001} cleavage. Values of VHN10 (15 indentations on five grains of synthetic Pt2HgSe3) are between 119 and 245 kg/mm2, with a mean value of 169 kg/mm2, corresponding to a Mohs hardness of approximately 3½. Under plane-polarized light, jacutingaite is light grey, has a moderate to distinct bireflectance, a bluish grey to rusty brown pleochroism, and a weak to distinct anisotropy; it does not exhibit internal reflections. Reflectance values of synthetic jacutingaite in air (Rmax, Rmin, in %) are: 51.1, 47.4 at 470 nm, 50.5, 48.2 at 546 nm, 49.6, 48.0 at 589 nm, and 47.8, 47.1 at 650 nm. Three electron-microprobe analyses of natural jacutingaite gave an average composition: Pt 37.30, Pd 5.91, Hg 25.72, Ag 0.16, Cu 0.82, and Se 31.48, total 101.39 wt.%, corresponding to the empirical formula (Pt1.46Pd0.42Cu0.10Ag0.01)∑1.99Hg0.98Se3.04 based on six atoms; the average result of nine analyses of synthetic jacutingaite is: Pt 47.14, Hg 24.24, and Se 28.62, for a total of 100.00 wt.%, corresponding to Pt2.00Hg1.00Se3.00. The mineral is trigonal, space group P3̄m1, with a 7.3477(2), c 5.2955(1) Å, V 247.59(1) Å3 and Z = 2. The crystal structure was solved and refined from the powder X-ray-diffraction data on synthetic Pt2HgSe3. Jacutingaite is isostructural with Pt4Tl2X6 (X = S, Se, or Te); no structural analogue is known as a mineral. Jacutingaite is structurally related to sudovikovite. The strongest lines in the X-ray powder-diffraction pattern of synthetic jacutingaite [d in Å(I)hkl] are: 5.2917(100)001, 2.7273(16)201, 2.4443(10)012, 2.0349(18)022, 1.7653(37)003, 1.3240(11)004 and 1.0449(11)025. The mineral is named after the specular-hematite-rich vein-type mineralization locally known as “jacutinga”, in which it occurs.

Description: Phase relations within the system Hg–Pt–Se were studied experimentally in the temperature range 400–800°C using the technique of evacuated silica-glass tubes. In this system, one ternary phase, Pt2HgSe3, jacutingaite, was recently described from the Cauê iron-ore deposit, Minas Gerais, Brazil. At 400°C, the following assemblages are stable: PtSe2 + HgSe + (SeL), PtSe2 + Pt2HgSe3 + HgSe, PtSe2 + Pt2HgSe3 + Pt5Se4, Pt2HgSe3 + Pt5Se4 + (Pt), Pt2HgSe3 + HgPt + (PtHg)ss, Pt2HgSe3 + HgPt + Hg2Pt, Pt2HgSe3 + Hg2Pt + Hg4Pt, Pt2HgSe3 + Hg4Pt + HgSe, and Hg4Pt + HgSe + (Hgv). Below 250°C, the phase HgPt is not stable, and the low-temperature assemblage Pt2HgSe3 + Hg2Pt + (PtHg)ss appears in the system. The amalgams Hg2Pt and Hg4Pt are likely to be found in nature.

Description: The phase equilibria in the system Pd–Pb–Te was studied by the evacuated-silica-tube method, electron-microprobe and X-ray powder-diffraction analyses. We investigated the 400°C isothermal section. The phase PdTe, the analogue of kotulskite, forms an extensive solid-solution and dissolves up to 30.2 at.% Pb; the phase Pd9Te4, the analogue of telluropalladinite, dissolve up to 2.3 at.% Pb, and the phase Pd20Te7 dissolves up to 5.5 at.% Pb. The phase Pd13Pb9 dissolves up to 2.1 at.% Te, and the phase Pd5Pb3, up to 7.7 at.% Te. Lead substitutes for tellurium. In the system Pd–Pb–Te, there are two ternary phases: Pd3Pb2Te2, the analogue of pašavaite, and Pd71Pb8Te21, not known to occur in nature. Pašavaite forms a stable association with kotulskite solid-solution in a compositional range from 25 to 30 at.% Pb and altaite. Phase Pd71Pb8Te21 forms a narrow solid-solution; its Pd content varies between 69.5 and 71.2 at.%, its Pb content, over the range 4.6 and 10.7, and its Te content, over the range 19.8 and 25.0 at.%. The phase Pd71Pb8Te21 forms stable assemblages with zvyagintsevite, telluropalladinitess, kotulskitess and Pd20Te7ss. Thus, such associations can be expected to occur in nature. Apart from the ternary phases, the binary phases PdPb2, PdPb, Pd13Pb9, Pd5Pb3, Pd3Te2, Pd20Te7, and Pd17Te4 can be expected to occur in nature in close association with other platinum-group minerals, in particular with known minerals of the system Pd–Pb–Te.

Description: Bowlesite is a new mineral discovered in the Merensky Reef of the Rustenburg Platinum Mine, Bushveld complex, South Africa. Bowlesite forms tiny grains (maximum dimension 20 μm). It is associated with sulfides including chalcopyrite, pyrrhotite and pentlandite, in contact with silicates including plagioclase, pyroxene- and minor serpentine-subgroup and amphibole-supergroup minerals. Bowlesite is brittle and has a metallic lustre. In plane-polarised light, bowlesite has a light bluish grey colour. It shows weak bireflectance, no pleochroism and has weak anisotropism. Internal reflections were not observed. Reflectance values of bowlesite in air (R1, R2 in %) are: 50.3–51.4 at 470 nm, 48.5–48.9 at 546 nm, 47.9–48.6 at 589 nm and 47.8–48.7 at 650 nm. Ten spot analyses of bowlesite give the average composition: Pt 56.85, Pd 0.02, Sn 34.03 and S 9.15, total 100.05 wt.%, corresponding to the empirical formula (Pt1.001Pd0.001)Σ1.002Sn0.997S1.001, based on 3 atoms per formula unit. The simplified formula is PtSnS. Due to the small size of bowlesite, the crystal structure was solved and refined from the powder X-ray-diffraction data of synthetic PtSnS. The calculated density is 10.06 g⋅cm–3. The mineral is orthorhombic, space group: Pca21 (#29) with a = 6.11511(10), b = 6.12383(10), c = 6.09667(11) Å, V = 228.31(1) Å3 and Z = 4. Bowlesite is isotypic with cobaltite, CoAsS. The origin of bowlesite is probably related to low-T exsolution of Pt–Sn phases from high-T sulfides crystallised from the sulfide melt. The mineral honours Dr. John Bowles (Manchester University, UK) for his contributions to ore mineralogy and mineral deposits related to mafic–ultramafic rocks.

Description: 〈div data-abstract-type="normal"〉〈p〉Mitrofanovite, Pt〈span〉3〈/span〉Te〈span〉4〈/span〉, is a new telluride discovered in low-sulfide disseminated ore in the East Chuarvy deposit, Fedorovo–Pana intrusion, Kola Peninsula, Russia. It forms anhedral grains (up to ~20 μm × 50 μm) commonly in intergrowths with moncheite in aggregates with lukkulaisvaaraite, kotulskite, vysotskite, braggite, keithconnite, rustenburgite and Pt–Fe alloys hosted by a chalcopyrite–pentlandite–pyrrhotite matrix. Associated silicates are: orthopyroxene, augite, olivine, amphiboles and plagioclase. Mitrofanovite is brittle; it has a metallic lustre and a grey streak. Mitrofanovite has a good cleavage, along {001}. In plane-polarised light, mitrofanovite is bright white with medium to strong bireflectance, slight pleochroism, and strong anisotropy on non-basal sections with greyish brown rotation tints; it exhibits no internal reflections. Reflectance values for the synthetic analogue of mitrofanovite in air (〈span〉R〈/span〉〈span〉o〈/span〉, 〈span〉R〈/span〉〈span〉e’〈/span〉 in %) are: 58.4, 54.6 at 470 nm; 62.7, 58.0 at 546 nm; 63.4, 59.1 at 589 nm; and 63.6, 59.5 at 650 nm. Fifteen electron-microprobe analyses of mitrofanovite gave an average composition: Pt 52.08, Pd 0.19, Te 47.08 and Bi 0.91, total 100.27 wt.%, corresponding to the formula (Pt〈span〉2.91〈/span〉Pd〈span〉0.02〈/span〉)〈span〉Σ2.93〈/span〉(Te〈span〉4.02〈/span〉Bi〈span〉0.05〈/span〉)〈span〉Σ4.07〈/span〉 based on 7 atoms; the average of eleven analyses on synthetic analogue is: Pt 52.57 and Te 47.45, total 100.02 wt.%, corresponding to Pt〈span〉2.94〈/span〉Te〈span〉4.06〈/span〉. The density, calculated on the basis of the formula, is 11.18 g/cm〈span〉3〈/span〉. The mineral is trigonal, space group 〈span〉R〈/span〉〈span〉〈span〉〈img data-mimesubtype="gif" data-type="simple" src="http://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20190902090145754-0317:S0026461X18001500:S0026461X18001500_inline1.gif"〉 〈span data-mathjax-type="texmath"〉 〈/span〉 〈/span〉〈/span〉〈span〉m〈/span〉, with 〈span〉a〈/span〉 = 3.9874(1), 〈span〉c〈/span〉 = 35.361(1) Å, 〈span〉V〈/span〉 = 486.91(2) Å〈span〉3〈/span〉 and 〈span〉Z〈/span〉 = 3. The crystal structure was solved and refined from the powder X-ray-diffraction data of synthetic Pt〈span〉3〈/span〉Te〈span〉4〈/span〉. Mitrofanovite is structurally and chemically related to moncheite (PtTe〈span〉2〈/span〉). The strongest lines in the powder X-ray diffraction pattern of synthetic mitrofanovite [〈span〉d〈/span〉 in Å (〈span〉I〈/span〉) (〈span〉hkl〈/span〉)] are: 11.790(23)(003), 5.891(100)(006), 2.851(26)(107), 2.137(16)(10〈span〉13〈/span〉), 2.039(18)(01〈span〉14〈/span〉), 1.574(24)(01〈span〉20〈/span〉), 1.3098(21)(00〈span〉27〈/span〉). The structural identity of natural mitrofanovite with synthetic Pt〈span〉3〈/span〉Te〈span〉4〈/span〉 was confirmed by electron backscatter diffraction measurements on the natural sample. The mineral name is chosen to honour Felix P. Mitrofanov, a Russian geologist who was among the first to discover platinum-group element mineralisation in the Fedorova–Pana complex.〈/p〉〈/div〉