Abstract
The new mineral plumbophyllite, Pb2Si4O10·H2O, is orthorhombic with space group Pbcn and cell parameters a = 13.2083(4), b = 9.7832(3), c = 8.6545(2) Å, V = 1118.33(5) Å3, and Z = 4. It occurs as colorless to pale blue prismatic crystals to 3 mm, with wedge-shaped terminations at the Blue Bell claims, about 11 km west of Baker, San Bernardino County, California. It is found in narrow veins in a highly siliceous hornfels in association with cerussite, chrysocolla, fluorite, goethite, gypsum, mimetite, opal, plumbotsumite, quartz, sepiolite, and wulfenite. The streak is white, the luster is vitreous, the Mohs hardness is about 5, and there is one perfect cleavage, {100}. The measured density is 3.96(5) g/cm3 and the calculated density is 3.940 g/cm3. Optical properties (589 nm): biaxial (+), α = 1.674(2), β = 1.684(2), γ = 1.708(2), 2V = 66(2)°, dispersion r > v (strong); X = b, Y = c, Z = a. Electron microprobe analysis provided PbO 60.25, CuO 0.23, SiO2 36.22 wt%, and CHN analysis provided H2O 3.29 wt% for a total of 99.99 wt%. Powder IR spectroscopy confirmed the presence of H2O and single-crystal IR spectroscopy indicated the H2O to be oriented perpendicular to the b axis. Raman spectra were also obtained. The strongest powder X-ray diffraction lines are [d (hkl) I]: 7.88(110)97, 6.63(200)35, 4.90(020)38, 3.623(202)100, 3.166(130)45, 2.938(312/411/222)57, 2.555(132/213)51, and 2.243(521/332)50. The atomic structure (R1 = 2.04%) consists of undulating sheets of silicate tetrahedra between which are located Pb atoms and channels containing H2O (and Pb2+ lone-pair electrons). The silicate sheets can be described as consisting of zigzag pyroxene-like (SiO3)n chains joined laterally into sheets with the unshared tetrahedral apices in successive chains pointed alternately up and down, a configuration also found in pentagonite.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Bonded interactions in silica polymorphs, silicates, and siloxane molecules
- Spatially heterogeneous burial and high-P/T metamorphism in the Crescent Formation, Olympic Peninsula, Washington
- Quantitative microstructural characterization of natrojarosite scale formed during high-pressure acid leaching of lateritic nickel ore
- Magnetic and microscopic characterization of magnetite nanoparticles adhered to clay surfaces
- Single crystal growth of wadsleyite
- Elastic behavior and phase stability of pollucite, a potential host for nuclear waste
- Crystal structure determination of anandite-2M mica
- Excess heat capacity and entropy of mixing in high structural state plagioclase
- Cannibalization of an amphibole-rich andesitic progenitor induced by caldera-collapse during the Matahina eruption: Evidence from amphibole compositions
- Experimental constraints on rutile saturation during partial melting of metabasalt at the amphibolite to eclogite transition, with applications to TTG genesis
- Mineralogical stability of phyllosilicates in hyperalkaline fluids: Influence of layer nature, octahedral occupation and presence of tetrahedral Al
- Plumbophyllite, a new species from the Blue Bell claims near Baker, San Bernardino County, California
- Simultaneous aluminum, silicon, and sodium coordination changes in 6 GPa sodium aluminosilicate glasses
- Mineral chemistry and alteration of rare earth element (REE) carbonates from alkaline pegmatites of Mount Malosa, Malawi
- The carbonatation of gypsum: Pathways and pseudomorph formation
- Calcium L2,3-edge XANES of carbonates, carbonate apatite, and oldhamite (CaS)
- Thermochemistry of a synthetic Na-Mg-rich triple-chain silicate: Determination of thermodynamic variables
- Change in compressibility of δ-AlOOH and δ-AlOOD at high pressure: A study of isotope effect and hydrogen-bond symmetrization
- Crystal structure and iron topochemistry of erionite-K from Rome, Oregon, U.S.A.
- First-principles energetics and structural relaxation of antigorite
- Letter. Evidence in favor of small amounts of ephemeral and transient water during alteration at Meridiani Planum, Mars
- Letter. Native aluminum: Does it exist?
- Letter. Hydration state and activity of aqueous silica in H2O-CO2 fluids at high pressure and temperature