Crystal Structure and Chemical Composition of Ludwigite from Vranovac Ore Deposit (Boranja Mountain, Serbia)

Abstract

The crystal structure of ludwigite from Vranovac ore deposit (Boranja Mt., Serbia) was refined using the X‐ray powder diffraction (XRPD) Rietveld method in the space group Pbam to a final RB=7.45% and RF=5.26%. It has the unit cell dimensions of: a= 9.2515(2) Å; b= 12.3109(2) Å; c= 3.03712 (7) Å; and V= 345.91(1) Å3. The calculated distances and angles are mostly in good agreement with the Mg2+‐Fe2+ substitutions across the M(1) and M(3) sites, as well as with the Fe3+‐Al3+ replacement in the M(4) site. However, the mean observed M(2)‐O distance is considerably shorter than prescribed, due to a slight increase of the Fe3+ content in the M(2) site. Such replacement was compensated by slight increase of the Fe2+ content in the M(4) site, resulting in the (Mg1.48Fe2+0.46Fe3+0.05Mn0.02)2.01 (Fe3+0.94Fe2+0.04Al0.02)1.00B1.00O5 composition. The formation temperature was estimated to be about 500–600°C. The influences of the various chemical compositions to the crystallographic parameters, M‐O distances, M(3) and M(4) sites shift, distortion parameters and estimated valences, were also studied and compared with other reference samples.

A possible connection between phosphate tungsten bronzes properties and Briggs-Rauscher oscillatory reaction response

“…Furthermore, it was previously shown that various tilting and orientations of the polyhedrons and polyhedral chains in other phosphate tungsten bronzes could derive the different space groups of crystallization [5], which makes this problem very complex from the structural aspect. The similar observations were also confirmed in our studies of other materials [38,39]. Although crystal structure refinements were beyond of the scope of this paper, different calculated crystallographic axis and angles between PWB, Li-PWB, and Ca-PWB (Table II) could be sufficient proof of the various tilting of their WO 6 octahedrons and PO 4 tetrahedrons.…”

Characterisation, axial anisotropy, and formation conditions of celestine minerals from the Jabal Eghei (Nuqay) late Neogene – Pleistocene volcanic province, southeastern edge of the Sirt Basin, southern Libya: Constraints on the mineralogical geothermometer

“…(v) The option that various structural variations within the samples could take place Although the crystal structure refinements are beyond the scope of this paper, our previous studies of diverse mineral species and solid solutions, have demonstrated that the different UCPs, polyhedral distortions, site occupancy factors, bond lengths, bond angles and valence units, could be influenced either by: (1) different inserted cations into the mineral structure; and/or by ( 2) diverse conditions of their formation, in particular, the temperature and pressure (Tančić 2017(Tančić , 2018Tančić and Kremenović, 2022;Tančić et al, 2012Tančić et al, , 2020Tančić et al, , 2023.…”

The Unconventional Peridotite-Related Mg-Fe-B Skarn of the El Robledal, SE Spain

“…These mineral assemblages are accompanied by their resulting altered minerals (i.e., humite, chondrodite, serpentine, phlogopite, calcite, and brucite). Thus, endogenous borates in Mg-skarn deposits are systematically developed on the outermost part of the contact aureole formed at the contact between igneous rocks and dolomite protolith [2,[6][7][8][9][10][11][12][13][14].…”