Hydrokenomicrolite, (□,H2O)2Ta2(O,OH)6(H2O), a new microlite-group mineral from Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil
-
Marcelo B. Andrade
,
Daniel Atencio
Abstract
Hydrokenomicrolite, (□,H2O)2Ta2(O,OH)6(H2O) or ideally □2Ta2[O4(OH)2](H2O), is a new microlite-group mineral approved by the CNMNC (IMA 2011-103). It occurs as an accessory mineral in the Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil. Associated minerals are: microcline, albite, quartz, muscovite, spodumene, “lepidolite”, cassiterite, tantalite-(Mn), monazite-(Ce), fluorite, “apatite”, beryl, “garnet”, epidote, magnetite, gahnite, zircon, “tourmaline”, bityite, and other microlite-group minerals under study. Hydrokenomicrolite occurs as euhedral octahedral crystals, occasionally modified by rhombododecahedra, untwinned, from 0.2 to 1.5 mm in size. The crystals are pinkish brown and translucent; the streak is white, and the luster is adamantine to resinous. It is non-fluorescent under ultraviolet light. Mohs hardness is 4½-5, tenacity is brittle. Cleavage is not observed; fracture is conchoidal. The calculated density is 6.666 g/cm3. The mineral is isotropic, ncalc = 2.055. The infrared spectrum contains bands of O-H stretching vibrations and H-O-H bending vibrations of H2O molecules. The chemical composition (n = 3) is [by wavelength-dispersive spectroscopy (WDS), H2O calculated from crystal-structure analysis, wt%]: CaO 0.12, MnO 0.27, SrO 4.88, BaO 8.63, PbO 0.52, La2O3 0.52, Ce2O3 0.49, Nd2O3 0.55, Bi2O3 0.57, UO2 4.54, TiO2 0.18, SnO2 2.60, Nb2O5 2.18, Ta2O5 66.33, SiO2 0.46, Cs2O 0.67, H2O 4.84, total 98.35. The empirical formula, based on 2 cations at the B site, is [□0.71(H2O)0.48Ba0.33Sr0.27U0.10Mn0.02Nd0.02Ce0.02La0.02Ca0.01 Bi0.01Pb0.01]Σ2.00 (Ta1.75Nb0.10Sn0.10Si0.04Ti0.01)Σ2.00[(O5.77(OH)0.23]Σ6.00[(H2O)0.97Cs0.03]Σ1.00. The strongest eight X-ray powderdiffraction lines [d in Å(I)(hkl)] are: 6.112(86)(111), 3.191(52)(311), 3.052(100)(222), 2.642(28)(400), 2.035(11)(511)(333), 1.869(29)(440), 1.788(10)(531), and 1.594(24)(622). The crystal structure refinement (R1 = 0.0363) gave the following data: cubic, Fd3̄m, a = 10.454(1) Å, V = 1142.5(2) Å3, Z = 8. The Ta(O,OH)6 octahedra are linked through all vertices. The refinement results and the approximate empirical bond-valences sums for the positions A (1.0 v.u.) and Y′ (0.5 v.u.), compared to valence calculations from electron microprobe analysis (EMPA) and ranges expected for H2O molecules, confirm the presence of H2O at the A(16d) site and displaced from the Y(8b) to the Y′(32e) position. The mineral is characterized by H2O dominance at the Y site, vacancy dominance at the A site, and Ta dominance at the B site.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Pressure-induced structural transformations in the low-cristobalite form of AlPO4
- Hydrokenomicrolite, (□,H2O)2Ta2(O,OH)6(H2O), a new microlite-group mineral from Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil
- Fluor-elbaite, Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3F, a new mineral species of the tourmaline supergroup
- Microtexture development during rapid cooling in three rhyolitic lava flows
- Microbial and inorganic control on the composition of clay from volcanic glass alteration experiments
- High-pressure experiments on phase transition boundaries between corundum, Rh2O3(II)- and CaIrO3-type structures in Al2O3
- Electronic structure effects in the vectorial bond-valence model
- Geometric analysis of radiation damage connectivity in zircon, and its implications for helium diffusion
- Superstructure, crystal chemistry, and cation distribution in filipstadite, a Sb5+-bearing, spinel-related mineral
- A high-temperature Brillouin scattering study on four compositions of haplogranitic glasses and melts: High-frequency elastic behavior through the glass transition
- Hydrogen isotope fractionation between coexisting hydrous melt and silicate-saturated aqueous fluid: An experimental study in situ at high pressure and temperature
- Eclogitic clasts with omphacite and pyrope-rich garnet in the NWA 801 CR2 chondrite
- Hydration properties of synthetic high-charge micas saturated with different cations: An experimental approach
- Quantitative analyses of powdered multi-minerallic carbonate aggregates using a portable Raman spectrometer
- Periodic ab initio bulk investigation of hydroxylapatite and type A carbonated apatite with both pseudopotential and all-electron basis sets for calcium atoms
- Coexisting pseudobrookite, ilmenite, and titanomagnetite in hornblende andesite of the Coleman Pinnacle flow, Mount Baker, Washington: Evidence for a highly oxidized arc magma
- Geochemistry of pyrochlore minerals from the Motzfeldt Center, South Greenland: The mineralogy of a syenite-hosted Ta, Nb deposit
- Phosphovanadylite-Ca, Ca[V4 4+P2O8(OH)8]·12H2O, the Ca analogue of phosphovanadylite-Ba
- The relationship between REE-Y-Nb-Th minerals and the evolution of an A-type granite, Wentworth Pluton, Nova Scotia
- Prewittite, KPb1.5Cu6Zn(SeO3)2O2Cl10, a new mineral from Tolbachik fumaroles, Kamchatka peninsula, Russia: Description and crystal structure
- Lucabindiite, (K,NH4)As4O6(Cl,Br), a new fumarole mineral from the “La Fossa” crater at Vulcano, Aeolian Islands, Italy
- Scottyite, the natural analog of synthetic BaCu2Si2O7, a new mineral from the Wessels mine, Kalahari Manganese Fields, South Africa
- Oxy-schorl, Na(Fe2 2+Al)Al6Si6O18(BO3)3(OH)3O, a new mineral from Zlatá Idka, Slovak Republic and Přibyslavice, Czech Republic
- Crystal chemistry and hydrogen bonding of rustumite Ca10(Si2O7)2(SiO4)(OH)2Cl2 with variable OH, Cl, F
- Oxy-vanadium-dravite, NaV3(V4Mg2)(Si6O18)(BO3)3(OH)3O: Crystal structure and redefinition of the “vanadium-dravite” tourmaline
- Lead-tellurium oxysalts from Otto Mountain near Baker, California: VIII. Fuettererite, Pb3Cu2+ 6 Te6+O6(OH)7Cl5, a new mineral with double spangolite-type sheets
- Lead-tellurium oxysalts from Otto Mountain near Baker, California: IX. Agaite, Pb3Cu2+Te6+O5(OH)2(CO3), a new mineral with CuO5-TeO6 polyhedral sheets
- Letter: Actinides in Geology, Energy, and the Environment. Evidence for nanocrystals of vorlanite, a rare uranate mineral, in the Nopal I low-temperature uranium deposit (Sierra Peña Blanca, Mexico)
Articles in the same Issue
- Pressure-induced structural transformations in the low-cristobalite form of AlPO4
- Hydrokenomicrolite, (□,H2O)2Ta2(O,OH)6(H2O), a new microlite-group mineral from Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil
- Fluor-elbaite, Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3F, a new mineral species of the tourmaline supergroup
- Microtexture development during rapid cooling in three rhyolitic lava flows
- Microbial and inorganic control on the composition of clay from volcanic glass alteration experiments
- High-pressure experiments on phase transition boundaries between corundum, Rh2O3(II)- and CaIrO3-type structures in Al2O3
- Electronic structure effects in the vectorial bond-valence model
- Geometric analysis of radiation damage connectivity in zircon, and its implications for helium diffusion
- Superstructure, crystal chemistry, and cation distribution in filipstadite, a Sb5+-bearing, spinel-related mineral
- A high-temperature Brillouin scattering study on four compositions of haplogranitic glasses and melts: High-frequency elastic behavior through the glass transition
- Hydrogen isotope fractionation between coexisting hydrous melt and silicate-saturated aqueous fluid: An experimental study in situ at high pressure and temperature
- Eclogitic clasts with omphacite and pyrope-rich garnet in the NWA 801 CR2 chondrite
- Hydration properties of synthetic high-charge micas saturated with different cations: An experimental approach
- Quantitative analyses of powdered multi-minerallic carbonate aggregates using a portable Raman spectrometer
- Periodic ab initio bulk investigation of hydroxylapatite and type A carbonated apatite with both pseudopotential and all-electron basis sets for calcium atoms
- Coexisting pseudobrookite, ilmenite, and titanomagnetite in hornblende andesite of the Coleman Pinnacle flow, Mount Baker, Washington: Evidence for a highly oxidized arc magma
- Geochemistry of pyrochlore minerals from the Motzfeldt Center, South Greenland: The mineralogy of a syenite-hosted Ta, Nb deposit
- Phosphovanadylite-Ca, Ca[V4 4+P2O8(OH)8]·12H2O, the Ca analogue of phosphovanadylite-Ba
- The relationship between REE-Y-Nb-Th minerals and the evolution of an A-type granite, Wentworth Pluton, Nova Scotia
- Prewittite, KPb1.5Cu6Zn(SeO3)2O2Cl10, a new mineral from Tolbachik fumaroles, Kamchatka peninsula, Russia: Description and crystal structure
- Lucabindiite, (K,NH4)As4O6(Cl,Br), a new fumarole mineral from the “La Fossa” crater at Vulcano, Aeolian Islands, Italy
- Scottyite, the natural analog of synthetic BaCu2Si2O7, a new mineral from the Wessels mine, Kalahari Manganese Fields, South Africa
- Oxy-schorl, Na(Fe2 2+Al)Al6Si6O18(BO3)3(OH)3O, a new mineral from Zlatá Idka, Slovak Republic and Přibyslavice, Czech Republic
- Crystal chemistry and hydrogen bonding of rustumite Ca10(Si2O7)2(SiO4)(OH)2Cl2 with variable OH, Cl, F
- Oxy-vanadium-dravite, NaV3(V4Mg2)(Si6O18)(BO3)3(OH)3O: Crystal structure and redefinition of the “vanadium-dravite” tourmaline
- Lead-tellurium oxysalts from Otto Mountain near Baker, California: VIII. Fuettererite, Pb3Cu2+ 6 Te6+O6(OH)7Cl5, a new mineral with double spangolite-type sheets
- Lead-tellurium oxysalts from Otto Mountain near Baker, California: IX. Agaite, Pb3Cu2+Te6+O5(OH)2(CO3), a new mineral with CuO5-TeO6 polyhedral sheets
- Letter: Actinides in Geology, Energy, and the Environment. Evidence for nanocrystals of vorlanite, a rare uranate mineral, in the Nopal I low-temperature uranium deposit (Sierra Peña Blanca, Mexico)
