Topic
Danburite
About: Danburite is a research topic. Over the lifetime, 73 publications have been published within this topic receiving 1302 citations.
Papers published on a yearly basis
Papers
TL;DR: In this article, the authors investigated matrix effects in secondary-ion mass spectrometric (SIMS) analysis of light elements (H, Li, Be, B, and F) in epoxy-mounted in a known crystallographic orientation relative to the primary-ion beam.
Abstract: Matrix effects in secondary-ion mass spectrometric (SIMS) analysis of light elements (H, Li, Be, B, and F) have been investigated in phenacite, kornerupine, danburite, axinite, spodumene, tourmaline, hambergite, and mica,all of which were epoxy-mounted in a known crystallographic orientation relative to the primary-ion beam. As reference chemical information, we used data from electron microprobe analysis (EMPA) and from single-crystal structure-refinement (SREF) on the same crystals used for SIMS. Quantification of secondary-ion intensities into concentrations was done using Si as the reference matrix element. The results indicate that matrix effects due to crystallographic orientation are <10% relative, or below analytical uncertainty for most analyzed elements. In dioctahedral mica, there is a difference in H/Si ion yield (IY) of -25% relative when the crystal is analyzed parallel and orthogonal to the main cleavage (which is perpendicular to the c axis). The magnitude of this effect is significant and higher than our SIMS accuracy for H in micas: ′10% relative. Among the analyzed elements, Be is affected least by matrix effects, even when present as a major element. The most significant chemical effects on SIMS analysis of H, Li, F, and B in silicates seem to be related to the Fe (+Mn) content of the matrix: the light-element IY decreases as the Fe (+Mn) content increases, as previously seen in tourmaline, axinite, and kornerupine. Silicon and Al seem to have complementary and opposite effects on IY with respect to Fe and Mn. The agreement between SIMS and SREF is close for most light elements when they are present as major constituents. The results of our study also show that analytical problems are still present for B by EMPA, and this technique may not be adequate to measure B accurately in some minerals.
69 citations
TL;DR: In this paper, the topological properties of the electron den- sity distributions for more than 20 geometry optimized molecules with SiO and GeO bonds with 3-, 4-, 6- and 8-coordinate Si and Ge cations were calculated.
Abstract: The topological properties of the electron den- sity distributions for more than 20 hydroxyacid, geometry optimized molecules with SiO and GeO bonds with 3-, 4-, 6- and 8-coordinate Si and Ge cations were calculated. Electronegativities calculated with the bond critical point (bcp) properties of the distributions indicate, for a given coordination number, that the electronegativity of Ge (1.85) is slightly larger than that of Si (1.80) with the electronegativities of both atoms increasing with de- creasing bond length. With an increase in the electron density, the curvatures and the Laplacian of the electron density at the critical point of each bond increase with de- creasing bond length. The covalent character of the bonds are assessed, using bond critical point properties and elec- tronegativity values calculated from the electron density distributions. A mapping of the (3, u3) critical points of the valence shell concentrations of the oxide anions for bridging SiOSi and GeOGe dimers reveals a location and disposition of localized nonbonding electron pairs that is consistent with the bridging angles observed for sil- icates and germanates. The bcp properties of electron den- sity distributions of the SiO bonds calculated for represen- tative molecular models of the coesite structure agree with average values obtained in X-ray diffraction studies of coesite and danburite to within5%.
58 citations
Journal Article•
55 citations
TL;DR: In this article, the authors investigated the pleochroic behaviour of two nominally anhydrous structurally similar minerals, danburite and An59 labradorite, in the region of the OH stretching frequencies.
Abstract: The pleochroic behaviour of two nominally anhydrous structurally similar minerals, danburite and An59 labradorite, was investigated in the region of the OH stretching frequencies. Danburite shows a sharp absorption band at 3540 cm−1, labradorite shows a broad band with an absorption maximum at 3230 cm−1. On the basis of the pleochroic scheme of theinfrared (IR) absorption spectra it is proposed that the OH dipoles in danburite are located within the symmetry plane showing a distinct orientation parallel to [010]; the OH groups in labradorite are oriented approximately perpendicular to (001). The proposed models are in accordance with bond valence calculations showing that in both framework structures the most deficient oxygens, O5 in danburite and O
C
m in labradorite, are partially replaced by OH.
54 citations
TL;DR: In this paper, the B K-edge X-ray absorption near-edge structure (XANES) spectra of two borates with tetrahedrally-coordinated B [[4]B; natural danburite (CaB2Si2O8) and synthetic boron phosphate (BPO4)] have been recorded in total electron yield (TEY) and fluorescence yield (FY) modes to investigate the surface and bulk structure of these materials.
Abstract: The B K-edge X-ray absorption near-edge structure (XANES) spectra of two borates with tetrahedrally-coordinated B [[4]B; natural danburite (CaB2Si2O8) and synthetic boron phosphate (BPO4)] have been recorded in total electron yield (TEY) and fluorescence yield (FY) modes to investigate the surface and bulk structure of these materials. The TEY XANES measurement shows that danburite is susceptible to surface damage involving conversion of [4]B sites to [3]B sites by reaction with moisture and/or mechanical abrasion (grinding, polishing, etc.). The bulk of the mineral is essentially unaffected. Commercial boron phosphate powder exhibits more extensive surface and bulk damage, which increases with air exposure but is recovered on heating at 650°C. In contrast to ELNES, the XANES technique is not affected by beam damage and when collected in the FY mode is capable of yielding meaningful information on the coordination and intermediate-range structure of B in borate and borosilicate materials.
44 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 1 |
| 2020 | 2 |
| 2019 | 1 |
| 2018 | 2 |
| 2017 | 5 |
| 2016 | 2 |