Browsing by Author "Shanks, FL"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Galeaclolusite, [Al6(AsO4)3(OH)9(H2O)4]⋅8H2O, a new bulachite-related mineral from Cap Garonne, France
    (Cambridge University Press, 2020-12-04) Grey, IE; Favreau, G; Mills, SJ; Mumme, WG; Bougerol, C; Brand, HEA; Kampf, AR; MacRae, CM; Shanks, FL
    Galeaclolusite, [Al6(AsO4)3(OH)9(H2O)4].8H2O, is a new secondary hydrated aluminium arsenate mineral from Cap Garonne, Var, France. It forms crusts and spheroids of white fibres up to 50 μm long by 0.4 μm wide and only 0.1 μm thick. The fibres are elongated along [001] and flattened on (100). The calculated density is 2.27 g.cm-3. Optically, galeaclolusite is biaxial with α = 1.550(5), β not determined, γ = 1.570(5) (white light) and partial orientation: Z = c (fibre axis). Electron microprobe analyses coupled with crystal structure refinement results gives an empirical formula based on 33 O atoms of Al5.72Si0.08As2.88O33H34.12. Galeaclolusite is orthorhombic, Pnma, with a = 19.855(4), b = 17.6933(11), c = 7.7799(5) A, V = 2733.0(7) Aand Z = 4. The crystal structure of galeaclolusite was established from its close relationship to bulachite and refined using synchrotron powder X-ray diffraction data. It is based on heteropolyhedral layers, parallel to (100), of composition Al6(AsO4)3(OH)9(H2O)4 and with H-bonded H2O between the layers. The layers contain [001] spiral chains of edge-shared octahedra, decorated with corner-connected AsO4 tetrahedra, that are the same as in the mineral liskeardite. © 2020. Published by Cambridge University Press on behalf of The Mineralogical Society of Great Britain and Ireland.
  • No Thumbnail Available
    Item
    The rockbridgeite group approved and a new member, ferrorockbridgeite, (Fe2+,Mn2+)2(Fe3+)3(PO4)3(OH)4(H2O), described from the Hagendorf Süd pegmatite, Oberpfalz, Bavaria
    (Schweizerbart Science Publishers, 2019-06-06) Grey, IE; Kampf, AR; Keck, E; Cashion, JD; MacRae, CM; Gozukara, Y; Peterson, VK; Shanks, FL
    The rockbridgeite group has been officially established by the IMA Commission on New Minerals, Nomenclature and Classification. The general formula is based on the structure and is A 2 B 3(PO4)3(OH, H2O)5, where A = the octahedrally coordinated M2 site, in which divalent cations are ordered, and B = the octahedrally coordinated M1 + M3 sites, which contain predominantly Fe3+, with trace Al. The different rockbridgeite-group minerals are distinguished by the occupancy of the A site. The ideal formula for rockbridgeite is F e 0.5 2 + Fe 0.5 3 + 2 Fe 3 3 + PO 4 3 OH 5 , that for frondelite is Mn 0.5 2 + Fe 0.5 3 + 2 Fe 3 3 + PO 4 3 OH 5 and that for plimerite is Z n 2 Fe 3 3 + P O 4 3 OH 4 ( H 2 O ) . In order to preserve the identity of frondelite and rockbridgeite within the structure-based formalism, these species correspond to mid-series compositions. We describe here the new end-member, ferrorockbridgeite, with dominant Fe2+ in the A site, from the Hagendorf Süd pegmatite mine, Oberpfalz, Bavaria. Electron microprobe analyses, coupled with Mössbauer spectroscopy, gives the empirical formula Fe 1.33 2 + Mn 0.52 2 + Zn 0.03 Ca 0.05 Fe 3.03 3 + Al 0.01 P 2.97 H 6.17 O 17 . The simplified formula is F e 2 + , M n 2 + 2 F e 3 3 + P O 4 3 OH 4 ( H 2 O ) . Ferrorockbridgeite is orthorhombic, space group Bbmm, with a = 13.9880(4), b = 16.9026(5), c = 5.1816(1) Å, V = 1225.1 Å3 and Z = 4. The six strongest lines in the X-ray powder diffraction pattern are [d meas/Å (I) (hkl)]: 4.853 (26) (101), 3.615 (24) (240), 3.465 (33) (301), 3.424 (39) (410), 3.205 (100) (321) and 1.603 (24) (642). Optically, ferrorockbridgeite is biaxial (–) with α = 1.763(3), β = 1.781(calc), γ = 1.797(3) (white light) and 2V (meas.) = 87(1)° from extinction data. The optical orientation is X = c, Y = a , Z = b. The pleochroism is X = blue green, Y = olive green, Z = yellow brown; X ≈ Y > Z. The rockbridgeite group has been officially established by the IMA Commission on New Minerals, Nomenclature and Classification. The general formula is based on the structure and is A 2 B 3(PO4)3(OH, H2O)5, where A = the octahedrally coordinated M2 site, in which divalent cations are ordered, and B = the octahedrally coordinated M1 + M3 sites, which contain predominantly Fe3+, with trace Al. The different rockbridgeite-group minerals are distinguished by the occupancy of the A site. The ideal formula for rockbridgeite is F e 0.5 2 + Fe 0.5 3 + 2 Fe 3 3 + PO 4 3 OH 5 , that for frondelite is Mn 0.5 2 + Fe 0.5 3 + 2 Fe 3 3 + PO 4 3 OH 5 and that for plimerite is Z n 2 Fe 3 3 + P O 4 3 OH 4 ( H 2 O ) . In order to preserve the identity of frondelite and rockbridgeite within the structure-based formalism, these species correspond to mid-series compositions. We describe here the new end-member, ferrorockbridgeite, with dominant Fe2+ in the A site, from the Hagendorf Süd pegmatite mine, Oberpfalz, Bavaria. Electron microprobe analyses, coupled with Mössbauer spectroscopy, gives the empirical formula Fe 1.33 2 + Mn 0.52 2 + Zn 0.03 Ca 0.05 Fe 3.03 3 + Al 0.01 P 2.97 H 6.17 O 17 . The simplified formula is F e 2 + , M n 2 + 2 F e 3 3 + P O 4 3 OH 4 ( H 2 O ) . Ferrorockbridgeite is orthorhombic, space group Bbmm, with a = 13.9880(4), b = 16.9026(5), c = 5.1816(1) Å, V = 1225.1 Å3 and Z = 4. The six strongest lines in the X-ray powder diffraction pattern are [d meas/Å (I) (hkl)]: 4.853 (26) (101), 3.615 (24) (240), 3.465 (33) (301), 3.424 (39) (410), 3.205 (100) (321) and 1.603 (24) (642). Optically, ferrorockbridgeite is biaxial (–) with α = 1.763(3), β = 1.781(calc), γ = 1.797(3) (white light) and 2V (meas.) = 87(1)° from extinction data. The optical orientation is X = c, Y = a , Z = b. The pleochroism is X = blue green, Y = olive green, Z = yellow brown; X ≈ Y > Z. The rockbridgeite group has been officially established by the IMA Commission on New Minerals, Nomenclature and Classification. The general formula is based on the structure and is A 2 B 3(PO4)3(OH, H2O)5, where A = the octahedrally coordinated M2 site, in which divalent cations are ordered, and B = the octahedrally coordinated M1 + M3 sites, which contain predominantly Fe3+, with trace Al. The different rockbridgeite-group minerals are distinguished by the occupancy of the A site. The ideal formula for rockbridgeite is F e 0.5 2 + Fe 0.5 3 + 2 Fe 3 3 + PO 4 3 OH 5 , that for frondelite is Mn 0.5 2 + Fe 0.5 3 + 2 Fe 3 3 + PO 4 3 OH 5 and that for plimerite is Z n 2 Fe 3 3 + P O 4 3 OH 4 ( H 2 O ) . In order to preserve the identity of frondelite and rockbridgeite within the structure-based formalism, these species correspond to mid-series compositions. We describe here the new end-member, ferrorockbridgeite, with dominant Fe2+ in the A site, from the Hagendorf Süd pegmatite mine, Oberpfalz, Bavaria. Electron microprobe analyses, coupled with Mössbauer spectroscopy, gives the empirical formula Fe 1.33 2 + Mn 0.52 2 + Zn 0.03 Ca 0.05 Fe 3.03 3 + Al 0.01 P 2.97 H 6.17 O 17 . The simplified formula is F e 2 + , M n 2 + 2 F e 3 3 + P O 4 3 OH 4 ( H 2 O ) . Ferrorockbridgeite is orthorhombic, space group Bbmm, with a = 13.9880(4), b = 16.9026(5), c = 5.1816(1) Å, V = 1225.1 Å3 and Z = 4. The six strongest lines in the X-ray powder diffraction pattern are [d meas/Å (I) (hkl)]: 4.853 (26) (101), 3.615 (24) (240), 3.465 (33) (301), 3.424 (39) (410), 3.205 (100) (321) and 1.603 (24) (642). Optically, ferrorockbridgeite is biaxial (–) with α = 1.763(3), β = 1.781(calc), γ = 1.797(3) (white light) and 2V (meas.) = 87(1)° from extinction data. The optical orientation is X = c, Y = a , Z = b. The pleochroism is X = blue green, Y = olive green, Z = yellow brown; X ≈ Y > Z. © 2018 E. Schweizerbart’sche Verlagsbuchhandlung