An Application of near Infrared Spectroscopy to the Study of the Selenite Minerals: Chalcomenite, Clinochalcomenite and Cobaltomenite

Abstract

The selection of five naturally occurring selenite minerals that contain two different transition metal ions, Cu 2+ and Co 2+ could be distinguished by near infrared spectroscopy. Dependence of composition on spectral properties is a key to mineral identification and differentiation of the members of the selenite group. The nature of the band positions and splitting of band components in the electronic spectra of Cu 2+ selenites in the region 12,400-8000 cm -1 are in conformity with octahedral geometry distortion. The two split components which are observed for the Co 2+ band near 9000 cm -1 in cobaltomenites are considered as the vibrational satellites of spin-allowed transition 4 T 1g (F) → 4 T 2g (F). Bands observed at 6950 cm -1 , 6810 cm -1 and 6700 cm -1 are the overtones of OH stretches of structural water in selenites and a strong absorption feature near 6700 cm -1 is the result of hydrogen bonding between (SeO 3 ) 2− and H 2 O. These bands are shifted in cobaltomenites. A sharp absorption band at 5170 cm -1 is a common feature in all the spectra of selenite minerals and is the contribution by the combinations of the OH vibrations of water molecules, n 3 and n 1 . A series of overlapping bands around 4500 and 4100 cm -1 is the result of the combination of the vibrational modes of (SeO 3 ) 2− ion in the minerals.

An application of near-infrared and mid-infrared spectroscopy to the study of selected tellurite minerals: xocomecatlite, tlapallite and rodalquilarite

“…This feature further supports the presence of molecular water in tellurites. Investigations on near-infrared spectra of selenites show that the bands in the region 7,500-4,000 are assigned to the overtones of water stretching vibrations and the vibrational units of (SeO 3 ) 2-and this study of selenite minerals; chalcomenite, clinochalcomenite and cobaltomenite by Frost et al [62], reveals the assignment of the sharp band observed at 5,170 cm -1 along with a low intensity band near 5,600 cm -1 that are derived from the combinational modes of OH vibrations of H 2 O molecules.…”

“…6 A 1g ? 4 T 1g transition band in minerals that contain ferric ion sites has been reported; 853 nm (11,710 cm -1 ) in andradite Ca 3 Fe 2 (SiO 4 ) 3 [61], hematite Fe 2 O 3 855 nm (11,695 cm -1 ), and 917 nm (10,895 cm -1 ) in lepidocrocite FeO(OH) [61,62].Ferric ion is responsible for the origin of the observed transition in Fig. 1c (12,300-8,800 cm -1 ).…”

Near Infrared Spectroscopy of Marble from Chillagoe, Australia and in Comparison with other Selected Natural Carbonates

“…22,23,25 NIR bands of marble at 4937 cm -1 , 5005 cm -1 , 5106 cm -1 , 5234 cm -1 and 5391 cm -1 are due to water vibrations. 21,37,38 The NIR spectrum of monohydrocalcite shows water bands at 4698 cm -1 , 4819 cm -1 , 5041 cm -1 and 5213 cm -1 . 21,37,38 The NIR spectra for marble and monohydrocalcite over the 5500-6200 cm -1 spectral range are displayed in Figure 7.…”

“…21,37,38 The NIR spectrum of monohydrocalcite shows water bands at 4698 cm -1 , 4819 cm -1 , 5041 cm -1 and 5213 cm -1 . 21,37,38 The NIR spectra for marble and monohydrocalcite over the 5500-6200 cm -1 spectral range are displayed in Figure 7. Dolomite does not show any intensity in this spectral region.…”

Characterisation of the Copper Arsenate Mineral Strashimirite, Cu8(AsO4)4(OH)4·4H2O, by near Infrared Spectroscopy

“…It was found that the hydroxyl unit was coordinated directly to the metal ion and formed hydrogen bonds to the arsenate anion. [50][51][52][53][54][55][56] the basic copper arsenates include a significant number of diagenetically related minerals. the aim of this paper is to present the near infrared (nIr) spectra of strashimirite and to relate the spectra to the structure of the mineral, the structure of which is uncertain.…”