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Raman spectroscopy has been applied to study a range of chromites ([Fe.sup.2+], Mg)(Cr, Al, [Fe.sup.3+])[.sup.2][O.sub.4] with variable chromium to aluminum to iron contents to ascertain conclusions about possible correlations between the chromium concentration and the position of the main Raman peaks within this mineral. Our intention was to examine chromite grains from different paragenesis, which vary significantly in their chromium content, to observe changes in the Raman spectra of this mineral. It was found that a negative correlation exists between the chromium number, calculated from the electron microprobe data, and the Raman peak number. Chromite grains with high chromium numbers show a low Raman peak, whereas samples with low chromium number show a higher Raman peak. Therefore, it is possible to infera relationship between the mineral composition and Raman bands for this type of spinel. The measurements have clearly shown that it is possible to draw precise conclusions about the chromium content of the mineral based on the Raman peak alone. This finding supports a possible application of portable Raman devices on Earth or in space for asteroids and planets., Raman spectroscopy has gained increasing importance in almost all areas of earth and material sciences. This is particularly true in studies of mineralogy, petrology, and volcanology. Raman spectroscopy has also [...]

Hydroxylbenyacarite, (H2O)2Mn2(Ti2Fe)(PO4)4[O(OH)](H2O)10⋅4H2O, is a new paulkerrite-group mineral from the El Criollo mine, Cordoba Province, Argentina (IMA2023–079). It was found in specimens of altered triplite, in association with bermanite, phosphosiderite, quartz, strengite and manganese oxides. Hydroxylbenyacarite occurs as light greenish-yellow rhombic tablets with dimensions of typically 20 to 50 μm, occasionally to 400 μm. The crystals are flattened on {010}, slightly elongated on [001] and bounded by the {111} and {010} forms. The calculated density is 2.32 g cm–3. Optically, hydroxylbenyacarite crystals are biaxial (+), with α = 1.608(3), β = 1.624(3), γ = 1.642(3) (measured in white light) and 2V(meas.) = 88(2)°. The calculated 2V is 87.5°. The empirical formula is Ca0.06A [K0.46(H2O)0.88□0.66]Σ2.00M1(Mn1.52Mg0.02Fe2+0.35□0.11)Σ2.00M2+ M 3(Fe3+1.21Al0.02Ti1.77)Σ3.00(PO4)4X [F0.16(OH)0.70O1.14]Σ2.00(H2O)10⋅3.77H2O. The average crystal structure for hydroxylbenyacarite has space group Pbca and unit cell parameters a = 10.5500(3) Å, b =20.7248(5) Å, c = 12.5023(3) Å, V = 2733.58(12) Å3 and Z = 4. It was refined using single-crystal data to wRobs = 0.074 for 2611 reflections with I > 3σ(I). The crystal structure contains corner-connected linear trimers of Ti-centred octahedra that share corners with PO4 tetrahedra to form 10-member rings parallel to (010). K+ cations and water molecules are located in interstitial sites within the rings. Additional corner-sharing of the PO4 tetrahedra with MnO2(H2O)4 octahedra occurs along [010] to complete the 3D framework structure. A new eight-coordinated interstitial site, previously unreported for paulkerrite-group minerals, is occupied by Ca2+ cations. Weak diffuse diffraction spots in reconstructed precession images for hydroxylbenyacarite violate the a and b glide plane extinctions for Pbca and are consistent with local, unit-cell-scale regions of monoclinic, P 21/ c structure, in which ordering of the interstitial K+ and Ca2+ cations occurs. [ABSTRACT FROM AUTHOR]

Rewitzerite, K(H2O)Mn2(Al2Ti)(PO4)4[O(OH)](H2O)10⋅4H2O, is a new monoclinic member of the paulkerrite group, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in specimens of altered zwieselite, in association with rockbridgeite. Rewitzerite forms clusters of colourless elongated hexagonal-shaped prisms, up to 0.1 mm long. The crystals are flattened on {010} and elongated along [100], with forms {010}, {001}, {111} and { $\bar{1}$ 11}. The calculated density is 2.33 g⋅cm–3. Optically, rewitzerite crystals are biaxial (+), with α = 1.585(2), β = 1.586(2), γ = 1.615(2) (measured in white light) and 2V(meas) = 25(2)°. The empirical formula from electron microprobe analyses and structure refinement is A1[K0.77(H2O)0.23]A2[H2O] M1(Mn2+0.82Mg0.64Fe3+0.43□0.11)Σ2.00M2+ M 3(Al1.51Ti4+1.06Fe3+0.43)Σ3.00(PO4)4X [(OH)0.54F0.42O1.04]Σ2.00(H2O)10⋅4H2O, where □ = vacancy. Rewitzerite has monoclinic symmetry with space group P 21/ c and unit-cell parameters a = 10.444(2) Å, b = 20.445(2) Å, c = 12.2690(10)Å, β = 90.17(3)°, V = 2619.8(6) Å3 and Z = 4. The crystal structure was refined using synchrotron single-crystal data to wR obs = 0.068 for 5894 reflections with I > 3σ(I). The crystal structure has the same topology as that for orthorhombic paulkerrite-group minerals but differs primarily in having an ordering of K+ and H2O molecules in different A sites, whereas they are disordered at a single A site in the orthorhombic members of the group. [ABSTRACT FROM AUTHOR]

A reef-associated mollusc fauna (gastropods and bivalves) and its facies context are described from latest Triassic (Sevatian–Rhaetian) reef carbonates of Austria (Rötelwand reef at Gaissau and Gosaukamm near Hallstatt). The studied carbonates from the Rötelwand reef consist of mollusc-rich rudstones, partly boundstones, which contain branched corals (Cycliphyllia and Retiophylia, Pinacophyllum), whereas coralline sponges are absent. The rich foraminiferid fauna that is associated with the reef builders consists of 11 genera; eight of these genera became extinct until the end of the Rhaetian. Associated with small patch reefs was a rich mollusc fauna with 19 gastropod species and 8 epifaunal bivalve species. The gastropod fauna is dominated by Microschiza rhaetica, Trochotoma praecursor, and the large growing Purpuroidea moosleitneri. Six gastropod species are new to science: Angulomphalus senowbarii sp. nov., Stuorella zapfei sp. nov., Hologyra callosa sp. nov., Microschiza rhaetica sp. nov., Angularia corallina sp. nov., and Purpuroidea moosleitneri sp. nov. Four Triassic gastropod species are placed in other genera (new combinations): Tylotrochus diversicostatus Wolff, 1967 and Eucycloscala epitoniformis Nützel and Senowbari-Daryan, 1999 are placed in Sadkia, Praelittorina sepkoskii Nützel and Erwin, 2004 in Microschiza, and Purpuroidea? minioi Leonardi, 1935 in Angularia Koken, 1892. Reversal of precedence is proposed for Angularia Koken, 1892 (Gastropoda) and Angularia Busk, 1881 (Bryozoa) under ICZN Art. 23.9. Although reefs suffered a catastrophic decline at the end of the Triassic, most of the studied reef-associated bivalve and gastropod genera survived into the Jurassic, indicating a considerable ecological plasticity of these groups. Only 12 out of 47 reef-associated mollusc genera became extinct (25.5%). This observation is at variance with earlier suggestions that taxa that were associated with reefs and carbonate substrata had a significantly higher extinction risk than level-bottom dwellers. However, extinction at the species level appears more severe; only three bivalve species but no gastropod species recorded in this fauna have records from the Jurassic. [ABSTRACT FROM AUTHOR]

The emergence of prebiotic organics was a mandatory step toward the origin of life. The significance of the exogenous delivery versus the in-situ synthesis from atmospheric gases is still under debate. We experimentally demonstrate that iron-rich meteoritic and volcanic particles activate and catalyse the fixation of CO2, yielding the key precursors of life-building blocks. This catalysis is robust and produces selectively aldehydes, alcohols, and hydrocarbons, independent of the redox state of the environment. It is facilitated by common minerals and tolerates a broad range of the early planetary conditions (150–300 °C, ≲ 10–50 bar, wet or dry climate). We find that up to 6 × 108 kg/year of prebiotic organics could have been synthesized by this planetary-scale process from the atmospheric CO2 on Hadean Earth. [ABSTRACT FROM AUTHOR]

This study explains the ionic conductivity in the mineral sugilite (idealized formula: Fe2Na2K[Li3Si12O30]) by resolving the dynamic disorder of both Li and Na cations using synchrotron X-ray single-crystal diffraction from 298 K to 1023 K. Non-zero anharmonic atomic displacement parameters at Na and Li sites at 1023 K adumbrated long-range charge transport routes for Li and Na cations commonly parallel to the (a–b) plane. Temperature-enhanced diffuse residuals in Fourier maps could unambiguously localize two interstitial sites suitable for Li, as well as three for Na. Each two-dimensional (2D) network of Li and Na interstitials was formed parallel to each other, providing Li and Na hopping pathways. The higher concentration of Na cations hopping in short distances of 2.0962(4)–2.3015(5) Å could be the main reason for the higher bulk conductivity values evaluated by impedance spectra of sugilite in comparison to those of its structural relatives with low Na contents, e.g., the mineral sogdianite ((Zr,Al,Fe)2Na0.36K[Li3Si12O30]). Bond valence sum landscape maps supported the critical role of dynamic disorder of Na+ over densely packed 2D interstitial networks for combined ionic conductivity along with mobile Li+ in sugilite-type compounds. [ABSTRACT FROM AUTHOR]

Pleysteinite, [(H 2 O) 0.5 K 0.5 ] 2 Mn 2 Al 3 (PO 4) 4 F 2 (H 2 O) 10 ⚫ 4H 2 O, is the aluminium analogue of benyacarite, from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in specimens of altered zwieselite, in association with nordgauite, fluellite, rockbridgeite, pyrite and columbite. Pleysteinite occurs as isolated and small aggregates of colourless, stubby prisms that are typically 10 to 30 µ m wide and up to 100 µ m long. The crystals are flattened on {010} and bounded by {111} , {100} and {001} planes. The calculated density is 2.34 g cm -3. Optically, pleysteinite crystals are biaxial (+), with α=1.566(2) , β=1.580(2) , γ=1.600(2) (measured in white light) and 2 V (meas.) = 80(1) ∘. The empirical formula from electron microprobe analyses and structure refinement is [(H 2 O) 0.50 K 0.50 ] 2 (Mn 1.20 Mg 0.49 Fe 0.272+ Zn 0.05) ∑2.01 (Al 1.63 Fe 0.203+ Ti 0.194+) ∑2.02 (Al 0.56 Ti 0.444+) (PO 4) 4.02 [F 0.58 O 0.31 (OH) 0.11 ] 2 (H 2 O) 10 ⚫ 3.92H 2 O. Pleysteinite has orthorhombic symmetry, with space group Pbca and unit-cell parameters a = 10.4133(8) Å, b=20.5242(17) Å, c=12.2651(13) Å, V=2621.4(4) Å 3 and Z=4. The crystal structure was refined using single-crystal data to wR obs=0.054 for 1692 reflections with I>3σ(I). The crystal structure contains corner-connected linear trimers of Al-centred octahedra that share corners with PO 4 tetrahedra to form 10-member rings parallel to (010). K + cations and water molecules are located in the rings. Additional corner-sharing of the PO 4 tetrahedra with Mn(H 2 O) 4 O 2 octahedra occurs along [010] to complete the 3D framework structure. [ABSTRACT FROM AUTHOR]

Whiteite-(CaMnFe), CaMn 2+ Fe 22+ Al 2 (PO 4) 4 (OH) 2 ⋅ 8H 2 O, is a new whiteite-subgroup member of the jahnsite group from the Hagendorf-Süd pegmatite, Oberpfalz, Bavaria, Germany. It was found in vugs in an altered feldspar area of a specimen composed predominantly of rockbridgeite, with hureaulite and relic triphylite. Other associated minerals in small vugs in the specimen were strengite and laueite. Whiteite-(CaMnFe) occurs as sprays and clusters of colourless to pale yellow, rod-like crystals, with diameters of typically 10 to 50 µ m and lengths up to ∼ 500 µ m. The crystals are flattened on {001} and elongated along [010]. The measured density is 2.80(2) g cm -3. Optically, whiteite-(CaMnFe) crystals are biaxial (+), with α=1.608(3) , β=1.612(3) , γ=1.624(3) and 2 V (meas.) = 59(1) ∘. The empirical formula from electron microprobe analyses and structure refinement is (Ca 0.70 Mn 0.30)Mn(Fe 1.232+ Mn 0.49 Mg 0.29 Zn 0.06) (Al 1.88 Fe 0.123+)(PO 4) 3.96 (OH) 2 (H 2 O) 8. Whiteite-(CaMnFe) is monoclinic, P2 /a , a=14.925(5) , b=7.0100(14) , c=10.053(2) Å, β=111.31(2) ∘ , V=979.9(4) Å 3 and Z=2. The crystal structure was refined using single-crystal data to wRobs=0.052 for 1613 reflections with I>3σ(I). Site occupancy refinements confirm the ordering of dominant Ca, Mn and Fe 2+ in the X , M 1 and M 2 sites, respectively, of the general jahnsite-group formula XM 1 M 2 2 M 3 2 (H 2 O) 8 (OH) 2 (PO 4) 4. [ABSTRACT FROM AUTHOR]

In this paper, we discuss information on crystal structure and morphology available from nuclear magnetic resonance (NMR) spectroscopy of 207Pb for the mineral family [Pb(4f)]2[Pb(6h)]3(AO4)3Cl with A = V (vanadinite), P (pyromorphite), and As (mimetite). The isotropic chemical shift of the 207Pb atoms at Wyckoff positions 4f and 6h was (re-)determined from either static single-crystal or magic angle spinning NMR experiments. This isotropic shift can be linearly correlated to the unit-cell volume within the mineral family, and in the wider context of lead-bearing minerals, to the shortest Pb-O distance for position 4f, in which 207Pb is solely coordinated by oxygen. By evaluating the number of resonances and their respective line widths in the 207Pb-NMR spectra of these three naturally grown minerals, it could be established that vanadinite forms single-domain macroscopic crystals with very small mosaicity, whereas pyromorphite crystals show NMR characteristics, which can be interpreted as being caused by significant mosaicity. In some instances, this mosaic spread could be quantitatively approximated by a Gaussian distribution with a standard deviation angle of σ = 5°. In contrast, our mimetite specimen was composed of multiple sub-crystals with a very high variability of orientations, going beyond mere mosaicity effects. By extending the NMR methodology presented here to other minerals, it may be possible to gain new insights about structure-property relationships and the morphology of natural grown minerals. [ABSTRACT FROM AUTHOR]

The chemical shift (CS) tensors for 31P and 207Pb in the natural mineral pyromorphite, Pb5(PO4)3Cl, were determined from orientation-dependent NMR spectra of a single crystal, and MAS-NMR spectroscopic experiments. For the two crystallographically independent lead atoms in the hexagonal crystal lattice with space group P63/ m, the NMR parameters derived from the tensor eigenvalues are δiso = -2172 ppm, ηcs = 0.08 for the 207Pb at Wyckoff position 6 h, and δiso = -2810 ppm, ηcs = 0.49 for position 4 f. For the 31P, which are also located at positions 6 h, δiso = -1.74 ppm and ηcs = 0.21 was found. A multi-parameter fit was utilized to extract the tensors from spectra acquired with one crystal rotation axis. The fit was sufficiently overdetermined to also include the orientation of the crystal rotation axis into the fit, which could not be determined by X-ray diffraction because of the high absorption coefficient of pyromorphite, caused by the large lead content, and the large crystal size. In contrast to the precisely determined tensor eigenvalues, the orientation of the eigenvectors in the crystal ab-plane of the pyromorphite system could only be resolved by using the results of density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]