A Raman and infrared spectroscopic study of Ca²⁺ dominant members of the mixite group from the Czech Republic

Abstract

and to molecular water, hydroxyl ions, and Cu-(O,OH) units in both minerals. O-H· · ·O hydrogen-bond lengths in zálesíite and calciopetersite structures were calculated with Libowitzky's empirical relation.

Theoretical and experimental study of the vibrational spectra of liroconite, Cu2Al(AsO4)(OH)4∙4H2O and bayldonite, Cu3Pb[O(AsO3OH)2(OH)2]

“…3g) exhibit two absorption maxima at 1100 and 1050 cm À1 vs. four liroconite bands at 1190, 1110, 1045 and 1020 cm À1 (Fig. 3c) (Table 1) [26,29].…”

“…3f-i, Table 1) bringing additional spectroscopic evidence for the absence of the H 2 O groups in the latter mineral. The 1520-1300 cm À1 region in bayldonite spectrum differs from the liroconite due to the presence of two doublets of characteristic (AsÀ ÀOH) bands arising from the (AsO 3 OH) 2-groups (Table 1) also registered in other arsenic complex hydrate minerals [24][25][26][27][28]. Namely, lowering of the symmetry of the AsO 4 group (due to the replacement of one O atom by an OH group) resulted in band splitting and enhanced number of AsÀ ÀO/OH stretching bands in bayldonite in comparison with the reduced number of AsÀ ÀO stretching bands in liroconite.…”

“…3c), two additional bands evolve at 641 and 612 cm À1 and are ascribed to water librational modes. Their assignment is reasonable because the observed wavenumber maxima are not typical for bayldonite (and other arsenate hydroxide minerals) and can be used as distinguishing bands between hydroxide [24,26,27,[29][30][31] and hydrate [32] arsenate minerals. The lowest peaks at 516, 487 and 461 cm À1 appear at somewhat lower frequencies compared to the corresponding peaks in studied bayldonite (Table 1), but are very close to the observed ones in sarkinite (510, 485 and 450 cm À1 ) [30] and are designated as 4 (AsO 4 ) bands.…”

Raman and infrared spectroscopic characterization of the arsenate‐bearing mineral tangdanite– and in comparison with the discredited mineral clinotyrolite

“…One possibility is that these bands are attributable to the acid arsenate unit (HOAsO 3 ) 2À ν 3 antisymmetric stretching mode and the ν 1 symmetric stretching mode. [14] Two intense Raman bands are found at 593 and 628 cm À1 . These bands are attributed to the (SO 4 ) 2À ν 4 bending modes.…”

Bismoclite (BiOCl) in the San Francisco de los Andes Bi–Cu–Au Deposit, Argentina. First Occurrence of a Bismuth Oxychloride in a Magmatic–Hydrothermal Breccia Pipe and Its Usefulness as an Indicator Phase in Mineral Exploration

“…Povarennykh (1978) [75] grouped the characteristic ν 3 and ν 4 vibrations of arsenates between 900-760 cm´1 and 420-310 cm´1 (Table 8). More recent studies documented that the tetrahedral (AsO 4 ) 3´e xhibits the ν 1 symmetric stretching vibration (A 1 ) at 818 cm´1, the ν 3 antisymmetric stretching vibration (F 2 ) at 786 cm´1, the ν4 bending vibration (F 2 ) at 405 cm´1, and the ν 2 symmetric bending vibration (E) at 350 cm´1 (Table 8) [76][77][78][79]. The position of IR absorption bands for (AsO 4 ) 3´m olecules of preisingerite from San Francisco de los Andes are in agreement with the studies cited above; the main difference between them is the interpretation of absorption peaks.…”