TY - JOUR

T1 - Erikjonssonite, (Pb32O21)[(V,Si,Mo,As)O4]4Cl9, a new mineral from the Kombat mine and structural classification of layered lead oxychlorides related to litharge

AU - Chukanov, Nikita V.

AU - Siidra, Oleg I.

AU - Polekhovsky, Yury S.

AU - Pekov, Igor V.

AU - Varlamov, Dmitry A.

AU - Ermolaeva, Vera N.

AU - Virus, Alla A.

PY - 2019/5

Y1 - 2019/5

N2 - The new lead oxychloride vanadate mineral erikjonssonite was discovered at the abandoned Kombat copper mine, Grootfontein district, Namibia, in association with hausmannite, calcite, glaucochroite, baryte, cerussite, and an insufficiently studied mineral chemically related to kombatite. Erikjonssonite forms thick tabular orange-red grains up to 0.3 ☓ 0.5 ☓ 0.5 mm3. The new mineral is brittle, has Mohs’ hardness of 2½ and an uneven fracture. Distinct cleavage on (010) is observed. Dcalc = 7.967 g/cm3. The reflectance values [Rmax,%/Rmin,%(λ, nm)] are: 20.4/18.9 (470), 19.0/17.6 (540), 18.5/17.1 (589), 18.0/16.6 (650). The infrared spectrum shows the absence of H-, C-and B-bearing groups. The chemical composition is (wavelength-dispersive mode electron microprobe, wt%): SiO2 0.86, V2O5 1.73, As2O5 0.96, MoO3 1.70, PbO 92.54, Cl 4.15, –O=Cl 0.94, total 101.00. The empirical formula based on 46 O + Cl atoms per formula unit (apfu) isPb31.50(V5+1.45Si1.09Mo6+0.90As5+0.63)∑4.07Cl8.89O37.11. The simplified formula is {(Pb32O21)[(V,Si,Mo,As)O4]4}Cl9. The crystal structure has been refined to R = 4.3% based on 7730 independent reflections with I >2σ(I). Erikjonssonite is monoclinic, C2/c, a = 23.200(5), b = 22.708(5), c = 12.418(3) Å, β = 102.167(4)°, V = 6395(2) Å3, and Z = 4. The structure of erikjonssonite is very similar to that of hereroite: in both minerals two [Pb32O21]22+ oxocentred blocks formed by OPb4 tetrahedra with inserted TO4 tetrahedral groups alternate with one chloride sheet. Average <T–O> bond lengths in the tetrahedral groups demonstrate very similar values which is interpreted as both T1 and T2 sites having mixed occupancies of V5+,Si4+,Mo6+ and As5+, unlike hereroite where <T–O> bond lengths are different and one site is exclusively occupied by As5+. The strongest lines of the powder X-ray diffraction pattern [d, Å(I, %)(hkl)] are: 3.501 (24) (531, 261), 2.980 (100) (551, 224), 2.794 (45) (802,514), 1.990 (24) (882), 1.977 (21) (606), 1.762 (20) (715, 8.10.2, 10.6.2), 1.648 (33) (11.5.5). The mineral is named in honour of the Swedish mineralogist Erik Jonsson (b. 1967). The holotype material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia. The concept of a “defect number (DN)” which is the number of O2– ions removed from the ideal [PbO] block per cavity area is suggested in order to classify the layered Pb oxychloride minerals structurally related to litharge.

AB - The new lead oxychloride vanadate mineral erikjonssonite was discovered at the abandoned Kombat copper mine, Grootfontein district, Namibia, in association with hausmannite, calcite, glaucochroite, baryte, cerussite, and an insufficiently studied mineral chemically related to kombatite. Erikjonssonite forms thick tabular orange-red grains up to 0.3 ☓ 0.5 ☓ 0.5 mm3. The new mineral is brittle, has Mohs’ hardness of 2½ and an uneven fracture. Distinct cleavage on (010) is observed. Dcalc = 7.967 g/cm3. The reflectance values [Rmax,%/Rmin,%(λ, nm)] are: 20.4/18.9 (470), 19.0/17.6 (540), 18.5/17.1 (589), 18.0/16.6 (650). The infrared spectrum shows the absence of H-, C-and B-bearing groups. The chemical composition is (wavelength-dispersive mode electron microprobe, wt%): SiO2 0.86, V2O5 1.73, As2O5 0.96, MoO3 1.70, PbO 92.54, Cl 4.15, –O=Cl 0.94, total 101.00. The empirical formula based on 46 O + Cl atoms per formula unit (apfu) isPb31.50(V5+1.45Si1.09Mo6+0.90As5+0.63)∑4.07Cl8.89O37.11. The simplified formula is {(Pb32O21)[(V,Si,Mo,As)O4]4}Cl9. The crystal structure has been refined to R = 4.3% based on 7730 independent reflections with I >2σ(I). Erikjonssonite is monoclinic, C2/c, a = 23.200(5), b = 22.708(5), c = 12.418(3) Å, β = 102.167(4)°, V = 6395(2) Å3, and Z = 4. The structure of erikjonssonite is very similar to that of hereroite: in both minerals two [Pb32O21]22+ oxocentred blocks formed by OPb4 tetrahedra with inserted TO4 tetrahedral groups alternate with one chloride sheet. Average <T–O> bond lengths in the tetrahedral groups demonstrate very similar values which is interpreted as both T1 and T2 sites having mixed occupancies of V5+,Si4+,Mo6+ and As5+, unlike hereroite where <T–O> bond lengths are different and one site is exclusively occupied by As5+. The strongest lines of the powder X-ray diffraction pattern [d, Å(I, %)(hkl)] are: 3.501 (24) (531, 261), 2.980 (100) (551, 224), 2.794 (45) (802,514), 1.990 (24) (882), 1.977 (21) (606), 1.762 (20) (715, 8.10.2, 10.6.2), 1.648 (33) (11.5.5). The mineral is named in honour of the Swedish mineralogist Erik Jonsson (b. 1967). The holotype material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia. The concept of a “defect number (DN)” which is the number of O2– ions removed from the ideal [PbO] block per cavity area is suggested in order to classify the layered Pb oxychloride minerals structurally related to litharge.

KW - Crystal structure

KW - Erikjonssonite

KW - Kombat mine

KW - Layered structures

KW - Lead oxychloride vanadate

KW - Litharge

KW - Namibia

KW - New mineral

KW - COMPLEX

KW - lead oxychloride vanadate

KW - litharge

KW - CRYSTAL-STRUCTURE

KW - BOND-VALENCE PARAMETERS

KW - new mineral

KW - layered structures

KW - crystal structure

KW - CHEMISTRY

KW - ASISITE

KW - erikjonssonite

UR - http://www.scopus.com/inward/record.url?scp=85069755508&partnerID=8YFLogxK

U2 - 10.1127/ejm/2019/0031-2854

DO - 10.1127/ejm/2019/0031-2854

M3 - Article

AN - SCOPUS:85069755508

VL - 31

SP - 619

EP - 628

JO - European Journal of Mineralogy

JF - European Journal of Mineralogy

SN - 0935-1221

IS - 3

ER -