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A multi-domain gem-grade Brazilian apatite
-
Tom Baikie
,
Martin K. Schreyer
Veröffentlicht/Copyright:
2. April 2015
Abstract
A gem-grade apatite from Brazil of general composition (Ca,Na)10[(P,Si,S)O4]6(F,Cl,OH)2 has been studied using single-crystal X-ray and neutron diffraction together with synchrotron powder X-ray diffraction. Earlier electron microscopy studies had shown the nominally single-phase apatite contains an abundant fluorapatite (F-Ap) host, together with chloro-hydroxylapatites (Cl/OH-Ap) guest phases that encapsulate hydroxylellestadite (OH-El) nanocrystals. While the latter features appear as small (200-400 nm) chemically distinct regions by transmission electron microscopy, and can be identified as separate phases by synchrotron powder X-ray diffraction, these could not be detected by singlecrystal X-ray and neutron analysis. The observations using neutron, X-ray and electron probes are however consistent and complementary. After refinement in the space group P63/m the tunnel anions F− are fixed at z = ¼ along <001>, while the anions Cl− and OH− are disordered, with the suggestion that O-H···O-H··· hydrogen-bonded chains form in localized regions, such that no net poling results. The major cations are located in the 4f AFO6 metaprism (Ca+Na), 6h ATO6X tunnel site (Ca only), and 6h BO4 tetrahedron (P+Si+S). The structural intricacy of this gem stone provides further evidence that apatite microstructures display a nano-phase separation that is generally unrecognized, with the implication that such complexity may impact upon the functionality of technological analogues.
Received: 2011-12-1
Accepted: 2012-5-30
Published Online: 2015-4-2
Published in Print: 2012-10-1
© 2015 by Walter de Gruyter Berlin/Boston
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Schlagwörter für diesen Artikel
Apatite;
X-ray diffraction;
Laue neutron diffraction;
synchrotron X-ray diffraction
Artikel in diesem Heft
- MSA Roebling medal lecture. Mineralogy, petrology, U-Pb geochronology, and geologic evolution of the Dabie-Sulu classic ultrahigh-pressure metamorphic terrane, East-Central China
- Brittle-ductile microfabrics in naturally deformed zircon: Deformation mechanisms and consequences for U-Pb dating
- In situ hot-stage AFM study of the dissolution of the barite (001) surface in water at 30–55 °C
- A multi-domain gem-grade Brazilian apatite
- High-temperature structural behaviors of anhydrous wadsleyite and forsterite
- Rates and mechanism of Y, REE, and Cr diffusion in garnet
- EPR discrimination of microcrystalline calcite geomaterials
- Crystal chemistry of Bi- and Mn-bearing vesuvianite from Långban, Sweden
- Cation ordering in Pb2+-bearing, Mn3+-rich pargasite from Långban, Sweden
- Long-term solid-phase fate of co-precipitated U(VI)-Fe(III) following biological iron reduction by Thermoanaerobacter
- The sulfur speciation in S-bearing minerals: New constraints by a combination of electron microprobe analysis and DFT calculations with special reference to sodalite-group minerals
- Simultaneous sound velocity and density measurements of NaCl at high temperatures and pressures: Application as a primary pressure standard
- The temperature and compositional dependence of disordering in Fe-bearing dolomites
- Quantifying crystallization and devitrification of rhyolites by means of X-ray diffraction and electron microprobe analysis
- Reactions of strontium anorthite with H2O+CaCl2 fluids at 500 °C and high pressure: Kinetic information from in situ synchrotron-radiation XRF analyses of the fluid
- Solubility of xenotime in a 2 M HCl aqueous fluid from 1.2 to 2.6 GPa and 300 to 500 °C
- Elastic and anelastic anomalies due to spin-state transitions in orthorhombic perovskite from isoelectronic behavior of Co3+ and Fe2+
- Accurate determination of ferric iron in garnets by bulk Mössbauer spectroscopy and synchrotron micro-XANES
- Re-investigation of the crystal structure of enstatite under high-pressure conditions
- Second-order P6̄c2-P31c transition and structural crystallography of the cyclosilicate benitoite, BaTiSi3O9, at high pressure
- High-pressure structural studies of eskolaite by means of single-crystal X-ray diffraction
- Almandine: Lattice and non-lattice heat capacity behavior and standard thermodynamic properties
- Witzkeite: A new rare nitrate-sulphate mineral from a guano deposit at Punta de Lobos, Chile
- Krasheninnikovite, KNa2CaMg(SO4)3F, a new mineral from the Tolbachik volcano, Kamchatka, Russia
- Crystal structure of pseudojohannite, with a revised formula, Cu3(OH)2[(UO2)4O4(SO4)2](H2O)12
- Letter. A natural photoelectrochemical cell for water splitting: Implications for early Earth and Mars
- Letter. In situ observation of the breakdown of magnetite (Fe3O4) to Fe4O5 and hematite at high pressures and temperatures
- Letter. The crystal structure of bartelkeite, with a revised chemical formula, PbFeGeVI(Ge2IVO7) (OH)2·H2O, isotypic with high-pressure P21/m lawsonite
