Abstract:A new mineral species, bernardevansite (IMA 2022-057), ideally Al 2 (Se 4+ O 3 ) 3 •6H 2 O, has been discovered from the El Dragón mine, Potosí Department, Bolivia. It occurs as aggregates or spheres of radiating bladed crystals on a matrix consisting of Co-bearing krut'aite-penroseite. Associated minerals are Co-bearing krutˊaite-penroseite, chalcomenite, and clinochalcomenite. Bernardevansite is colorless in transmitted light, transparent with white streak and vitreous luster. It is brittle and has a Mohs ha… Show more
“…Later solutions rich in Bi, Pb and Hg resulted in the crystallisation of minerals such as clausthalite, petrovicite, watkinsonite and the recently described minerals eldragónite, Cu 6 BiSe 4 (Se 2 ) (Paar et al ., 2012), grundmannite, CuBiSe 2 (Förster et al ., 2016), hansblockite, (Cu,Hg)(Bi,Pb)Se 2 (Förster et al ., 2017), cerromojonite, CuPbBiSe 3 (Förster et al ., 2018) and nickeltyrrellite, CuNi 2 Se 4 (Förster et al ., 2019). Oxidation produced a wide range of secondary Se-bearing minerals, such as favreauite, PbBiCu 6 O 4 (SeO 3 ) 4 (OH)⋅H 2 O (Mills et al ., 2014), alfredopetrovite, Al 2 (Se 4+ O 3 ) 3 ⋅6H 2 O (Kampf et al ., 2016b), franksousaite, PbCu(Se 6+ O 4 )(OH) 2 (Yang et al ., 2022), bernardevansite, Al 2 (Se 4+ O 3 ) 3 ⋅6H 2 O (Yang et al ., 2023b), petermegawite, Al 6 (Se 4+ O 3 ) 3 [SiO 3 (OH)](OH) 9 ⋅10H 2 O (Yang et al ., 2023c) and the new mineral guangyuanite, described herein. Figure 1.The specimen on which the new mineral guangyuanite, indicated by the blue arrow, was found.…”
Section: Sample Description and Experimental Methodsmentioning
A new mineral species, guangyuanite, ideally Pb3Cl3(Se4+O3)(OH), was discovered from the El Dragón mine, Antonio Quijarro Province, Potosí Department, Bolivia. It occurs as equant crystals. Associated minerals are Co-bearing krut'aite–penroseite, chalcomenite, schmiederite, olsacherite, phosgenite, anglesite, cerussite and franksousaite. Guangyuanite is pale yellow–brown in transmitted light, transparent with white streak and vitreous lustre. It is brittle and has a Mohs hardness of ~3. No parting or cleavage was observed. The calculated density is 7.63 g/cm3. An electron microprobe analysis yielded an empirical formula [based on 7 (O + Cl) atoms per formula unit] of Pb3.02Cl3.01(Se4+0.99O3)(OH), which can be simplified to Pb3Cl3(Se4+O3)(OH).
Guangyuanite is isostructural with synthetic Pb3Br3(Se4+O3)(OH). It is orthorhombic, with space group Pnma and unit-cell parameters a = 11.0003(5), b = 10.6460(5), c = 7.7902 Å, V = 912.31(6) Å3 and Z = 4. The crystal structure of guangyuanite contains two symmetrically-distinct Pb (Pb1 and Pb2) cations, with Pb1 coordinated by eight anions (4O + 4Cl) and Pb2 only by six anions (3O + 3Cl), forming a marked lopsided coordination typical of Pb2+ with a stereochemically active 6s2 lone electron pair. The Se4+ cation forms a typical [Se4+O3] trigonal pyramid. The crystal structure of guangyuanite can be described as consisting of layers of edge-sharing [Pb1O4Cl4] polyhedra parallel to (100). These layers are linked together by sharing polyhedral corners (Cl atoms), as well as [Pb2O3Cl3] and [Se4+O3] groups. Chemically, guangyuanite is one of six lead chloride selenite minerals reported thus far and closely related to orlandiite Pb3Cl4(Se4+O3)⋅H2O.
“…Later solutions rich in Bi, Pb and Hg resulted in the crystallisation of minerals such as clausthalite, petrovicite, watkinsonite and the recently described minerals eldragónite, Cu 6 BiSe 4 (Se 2 ) (Paar et al ., 2012), grundmannite, CuBiSe 2 (Förster et al ., 2016), hansblockite, (Cu,Hg)(Bi,Pb)Se 2 (Förster et al ., 2017), cerromojonite, CuPbBiSe 3 (Förster et al ., 2018) and nickeltyrrellite, CuNi 2 Se 4 (Förster et al ., 2019). Oxidation produced a wide range of secondary Se-bearing minerals, such as favreauite, PbBiCu 6 O 4 (SeO 3 ) 4 (OH)⋅H 2 O (Mills et al ., 2014), alfredopetrovite, Al 2 (Se 4+ O 3 ) 3 ⋅6H 2 O (Kampf et al ., 2016b), franksousaite, PbCu(Se 6+ O 4 )(OH) 2 (Yang et al ., 2022), bernardevansite, Al 2 (Se 4+ O 3 ) 3 ⋅6H 2 O (Yang et al ., 2023b), petermegawite, Al 6 (Se 4+ O 3 ) 3 [SiO 3 (OH)](OH) 9 ⋅10H 2 O (Yang et al ., 2023c) and the new mineral guangyuanite, described herein. Figure 1.The specimen on which the new mineral guangyuanite, indicated by the blue arrow, was found.…”
Section: Sample Description and Experimental Methodsmentioning
A new mineral species, guangyuanite, ideally Pb3Cl3(Se4+O3)(OH), was discovered from the El Dragón mine, Antonio Quijarro Province, Potosí Department, Bolivia. It occurs as equant crystals. Associated minerals are Co-bearing krut'aite–penroseite, chalcomenite, schmiederite, olsacherite, phosgenite, anglesite, cerussite and franksousaite. Guangyuanite is pale yellow–brown in transmitted light, transparent with white streak and vitreous lustre. It is brittle and has a Mohs hardness of ~3. No parting or cleavage was observed. The calculated density is 7.63 g/cm3. An electron microprobe analysis yielded an empirical formula [based on 7 (O + Cl) atoms per formula unit] of Pb3.02Cl3.01(Se4+0.99O3)(OH), which can be simplified to Pb3Cl3(Se4+O3)(OH).
Guangyuanite is isostructural with synthetic Pb3Br3(Se4+O3)(OH). It is orthorhombic, with space group Pnma and unit-cell parameters a = 11.0003(5), b = 10.6460(5), c = 7.7902 Å, V = 912.31(6) Å3 and Z = 4. The crystal structure of guangyuanite contains two symmetrically-distinct Pb (Pb1 and Pb2) cations, with Pb1 coordinated by eight anions (4O + 4Cl) and Pb2 only by six anions (3O + 3Cl), forming a marked lopsided coordination typical of Pb2+ with a stereochemically active 6s2 lone electron pair. The Se4+ cation forms a typical [Se4+O3] trigonal pyramid. The crystal structure of guangyuanite can be described as consisting of layers of edge-sharing [Pb1O4Cl4] polyhedra parallel to (100). These layers are linked together by sharing polyhedral corners (Cl atoms), as well as [Pb2O3Cl3] and [Se4+O3] groups. Chemically, guangyuanite is one of six lead chloride selenite minerals reported thus far and closely related to orlandiite Pb3Cl4(Se4+O3)⋅H2O.
A polymorph of PbSe4+O3, designated as molybdomenite-P21/c, has been discovered from the El Dragón mine, Potosí Department, Bolivia. It occurs as thin-bladed crystals. Associated minerals are Co-bearing krut’aite–penroseite, chalcomenite, and dolomite. Molybdomenite- P21/c is pale yellow in transmitted light and has a greasy luster. It is brittle and has a Mohs hardness of 3. No cleavage was observed. The calculated density is 7.034 g/cm3. An electron microprobe analysis yielded an empirical formula (based on 3 O apfu) of Pb1.00Se1.00O3.
Molybdomenite-P21/c is the natural counterpart of synthetic α-PbSe4+O3, which is dimorphous with grandfathered P21/m molybdomenite (or β-PbSe4+O3). It is monoclinic with space group P21/c and unit-cell parameters a = 9.154(8), b = 8.071(6), c = 8.780(7) Å, β = 103.15(8) °, and V = 631.6(6) Å3. The crystal structure of molybdomenite-P21/c consists of two symmetrically distinct Pb (Pb1 and Pb2), two Se (Se1 an Se2), and six O atoms. Each Se4+ cation is bonded to three O atoms, forming a typical (Se4+O3)2− trigonal pyramid. Both Pb1 and Pb2 atoms are coordinated by nine O atoms. Each [PbO9] polyhedron is linked to six (SeO3)2− pyramids, three by sharing edges and three by sharing corners. The [PbO9] polyhedra are connected to one another through sharing edges and by (SeO3)2− groups, giving rise to a complex three-dimensional net system. Topologically, the crystal structure of molybdomenite-P21/c is identical to that of molybdomenite. Raman spectroscopic measurements reveal that there is only one strong peak centered at 790 cm−1, attributable to the Se4+–O symmetric stretching vibrations within the (SeO3)2− groups, for molybdomenite, whereas there are two such strong peaks, one at 788 cm−1 and the other at 804 cm−1, for molybdomenite-P21/c.
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