TY - JOUR

T1 - Mineralogical data on angelaite, Cu2AgPbBiS4, from the Los Manantiales District, Chubut, Argentina

AU - Topa, D.

AU - Paar, W.H.

AU - Putz, H.

AU - Zagler, G.

AU - Brodtkorb, M.K.de

AU - Stanley, C.J.

AU - Roberts, A.C.

AU - Makovicky, Emil

PY - 2010

Y1 - 2010

N2 - Angelaite, ideally Cu2AgPbBiS4, occurs as a hypogene mineral in polymetallic ores at the Ángela groups of veins in the mining district of Los Manantiales, in the province of Chubut, Argentina. The new mineral species is predominantly associated with pyrite, sphalerite, chalcopyrite, hematite, native gold and galena; less common associates are aikinite, wittichenite, miharaite and cervelleite. Angelaite forms subhedral, commonly oriented inclusions in galena; these may attain a size of up to 200 3 50 mm. The mineral is grey in color with a brownish tint, opaque, and lacks internal reflections. It has a metallic luster and a dark grey streak. The VHN10 ranges between 245 and 263 kg/mm3 (mean 253), corresponding to a Mohs hardness of 3½. In plane-polarized light, it is strongly bireflectant and pleochroic from light grey with a brownish tint to light cream with a greenish tint. Angelaite is strongly anisotropic, with rotation tints in shades of pale grey, deep green and deep blue. We provide the measured values of reflectance in air and oil. The average of 23 electron-microprobe analyses is: Cu 16.7(3), Ag 13.4(2), Pb 27.8(6), Bi 26.6(5), S 16.0(2), total 100.5(5) wt.%, equivalent to Cu2.07Ag0.97Pb1.05Bi1.00S3.91. The ideal formula (on the basis of nine atoms) is Cu2AgPbBiS4, which requires Cu 16.31, Ag 13.84, Pb 26.58, Bi 26.81, S 16.45, total 100 wt.%. Angelaite is orthorhombic, with a 12.734(5), b 4.032(1), c 14.633(5) Å, V 751.8(5) Å3, space group Pnma and Z = 4. The calculated density is 6.934 g/cm3. It is a homeotype of galenobismutite, with Cu and Ag replacing one of the Bi positions in a complicated way. The strongest eight lines in the calculated powder-diffraction pattern [d in Å(I)(hkl)] are 3.672(100)(032), 3.660(64)(004), 3.407(60)(120), 3.319(62)(121), 3.317(62)(121), 3.111(69)(041), 3.022(72)(113) and 3.017(72)(113). The mineral is named after the location. Both the mineral and its name were approved by the CNMNC (IMA #2003–064).

AB - Angelaite, ideally Cu2AgPbBiS4, occurs as a hypogene mineral in polymetallic ores at the Ángela groups of veins in the mining district of Los Manantiales, in the province of Chubut, Argentina. The new mineral species is predominantly associated with pyrite, sphalerite, chalcopyrite, hematite, native gold and galena; less common associates are aikinite, wittichenite, miharaite and cervelleite. Angelaite forms subhedral, commonly oriented inclusions in galena; these may attain a size of up to 200 3 50 mm. The mineral is grey in color with a brownish tint, opaque, and lacks internal reflections. It has a metallic luster and a dark grey streak. The VHN10 ranges between 245 and 263 kg/mm3 (mean 253), corresponding to a Mohs hardness of 3½. In plane-polarized light, it is strongly bireflectant and pleochroic from light grey with a brownish tint to light cream with a greenish tint. Angelaite is strongly anisotropic, with rotation tints in shades of pale grey, deep green and deep blue. We provide the measured values of reflectance in air and oil. The average of 23 electron-microprobe analyses is: Cu 16.7(3), Ag 13.4(2), Pb 27.8(6), Bi 26.6(5), S 16.0(2), total 100.5(5) wt.%, equivalent to Cu2.07Ag0.97Pb1.05Bi1.00S3.91. The ideal formula (on the basis of nine atoms) is Cu2AgPbBiS4, which requires Cu 16.31, Ag 13.84, Pb 26.58, Bi 26.81, S 16.45, total 100 wt.%. Angelaite is orthorhombic, with a 12.734(5), b 4.032(1), c 14.633(5) Å, V 751.8(5) Å3, space group Pnma and Z = 4. The calculated density is 6.934 g/cm3. It is a homeotype of galenobismutite, with Cu and Ag replacing one of the Bi positions in a complicated way. The strongest eight lines in the calculated powder-diffraction pattern [d in Å(I)(hkl)] are 3.672(100)(032), 3.660(64)(004), 3.407(60)(120), 3.319(62)(121), 3.317(62)(121), 3.111(69)(041), 3.022(72)(113) and 3.017(72)(113). The mineral is named after the location. Both the mineral and its name were approved by the CNMNC (IMA #2003–064).

U2 - 10.3749/canmin.48.1.139

DO - 10.3749/canmin.48.1.139

M3 - Journal article

VL - 48

SP - 139

EP - 144

JO - Canadian Mineralogist

JF - Canadian Mineralogist

SN - 0008-4476

IS - 1

ER -