Browsing by Author "Keck, E"

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    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