Reference:
▪ Förster, H-J., Bindi, L., Stanley, C.J., Grundmann, G. (2017): Hansblockite, (Cu,Hg)(Bi,Pb)Se2, the monoclinic polymorph of grundmannite: a new mineral from the Se mineralization at El Dragόn (Bolivia). Mineralogical Magazine, 81, 629–640.
Abstract:
Hansblockite, ideally (Cu,Hg)(Bi,Pb)Se2, is a new selenide from the El Dragόn mine, Bolivia. It typically occurs in thin plates subparallel intergrown with two unnamed Cu−Hg−Pb−Bi−Se species, clausthalite, Co-rich penroseite, and petrovicite. It also forms sub to anhedral grains up to 150 μm in length and 50 μm in width. Hansblockite is non fluorescent, black and opaque with a metallic luster and black streak. It is brittle, with an irregular fracture and no obvious parting and cleavage. The VHN20 values range from 37 to 50 (mean 42) kg mm−2 (Mohs hardness 2− 2½). In plane-polarized incident light, hansblockite is cream to light grey in colour, weakly bireflectant and weakly pleochroic from greyish cream to cream. Under crossed polars, hansblockite is weakly anisotropic with khaki to pale blue rotation tints. The reflectance values in air for the 23 COM standard wavelengths are: 47.3−48.1 (470 nm), 47.4−49.9 (546 nm), 47.1−49.0 (589 nm), and 46.6−48.5 (650 nm). The mean composition is Cu 9.31, Ag 0.73, Hg 11.43, Pb 3.55, Ni 0.17, Co 0.03, Bi 31.17, Se 34.00, total 100.39 wt.%. The mean empirical formula (based on 4 atoms pfu) is (Cu0.68Hg0.27Ag0.03Ni0.01)Σ=0.99(Bi0.69 Pb0.31)Σ=1.00Se2.01.The simplified formula is (Cu,Hg)(Bi,Pb)Se2. Hansblockite is monoclinic, space group P21/c, with a 6.853(1) Å, b 7.635(1) Å, c 7.264(1) Å, β 97.68(1)°, V 376.66(9) Å3, and Z = 4. Density is 8.26 g cm−3. The five strongest X-ray powder-diffraction lines [d in Å (I/I0) (hkl)] are: 3.97 (90) (111), 3.100 (40) (-121), 2.986 (100) (-211), 2.808 (50) (112), and 2.620 (50) (022). Hansblockite represents the monoclinic polymorph of grundmannite, CuBiSe2, with Hg and Pb being essential in stabilizing the monoclinic structure via the coupled substitution Cu+ + Bi3+ ⇔ Hg2+ + Pb2+. The mineral name is in honour of Hans Block (1881−1953), in recognition of his important role in boosting Bolivian ore mining.
▪ Förster, H-J., Bindi, L., Stanley, C.J., Grundmann, G. (2017): Hansblockite, (Cu,Hg)(Bi,Pb)Se2, the monoclinic polymorph of grundmannite: a new mineral from the Se mineralization at El Dragόn (Bolivia). Mineralogical Magazine, 81, 629–640.
Abstract:
Hansblockite, ideally (Cu,Hg)(Bi,Pb)Se2, is a new selenide from the El Dragόn mine, Bolivia. It typically occurs in thin plates subparallel intergrown with two unnamed Cu−Hg−Pb−Bi−Se species, clausthalite, Co-rich penroseite, and petrovicite. It also forms sub to anhedral grains up to 150 μm in length and 50 μm in width. Hansblockite is non fluorescent, black and opaque with a metallic luster and black streak. It is brittle, with an irregular fracture and no obvious parting and cleavage. The VHN20 values range from 37 to 50 (mean 42) kg mm−2 (Mohs hardness 2− 2½). In plane-polarized incident light, hansblockite is cream to light grey in colour, weakly bireflectant and weakly pleochroic from greyish cream to cream. Under crossed polars, hansblockite is weakly anisotropic with khaki to pale blue rotation tints. The reflectance values in air for the 23 COM standard wavelengths are: 47.3−48.1 (470 nm), 47.4−49.9 (546 nm), 47.1−49.0 (589 nm), and 46.6−48.5 (650 nm). The mean composition is Cu 9.31, Ag 0.73, Hg 11.43, Pb 3.55, Ni 0.17, Co 0.03, Bi 31.17, Se 34.00, total 100.39 wt.%. The mean empirical formula (based on 4 atoms pfu) is (Cu0.68Hg0.27Ag0.03Ni0.01)Σ=0.99(Bi0.69 Pb0.31)Σ=1.00Se2.01.The simplified formula is (Cu,Hg)(Bi,Pb)Se2. Hansblockite is monoclinic, space group P21/c, with a 6.853(1) Å, b 7.635(1) Å, c 7.264(1) Å, β 97.68(1)°, V 376.66(9) Å3, and Z = 4. Density is 8.26 g cm−3. The five strongest X-ray powder-diffraction lines [d in Å (I/I0) (hkl)] are: 3.97 (90) (111), 3.100 (40) (-121), 2.986 (100) (-211), 2.808 (50) (112), and 2.620 (50) (022). Hansblockite represents the monoclinic polymorph of grundmannite, CuBiSe2, with Hg and Pb being essential in stabilizing the monoclinic structure via the coupled substitution Cu+ + Bi3+ ⇔ Hg2+ + Pb2+. The mineral name is in honour of Hans Block (1881−1953), in recognition of his important role in boosting Bolivian ore mining.