Raman spectroscopy of natural oxalates at 298 and 77 K

Abstract

A comparative study of a suite of natural oxalates including weddellite, whewellite, moolooite, humboldtine, glushinskite, natroxalate and oxammite was undertaken using Raman spectroscopy at 298 and 77 K. Oxalates are found as films on host rocks as a result of heavy metal expulsion by primitive plants such as lichens and fungi. The minerals are characterized by the Raman position of the CO stretching vibration, which is cation sensitive. The band is observed at 1468 cm−1 for weddellite, 1464 cm−1 for whewellite, 1489 cm−1 for moolooite, 1489 cm−1 for humboldtine, 1471 cm−1 for glushinskite, 1456 cm−1 for natroxalate and 1473 cm−1 for oxammite. Except for oxammite, the infrared and Raman spectra are mutually exclusive, indicating that the minerals are bidentate and planar. Significant differences are observed in the CC stretching region and in the OCO bending region centred upon 910 and 860 cm−1, respectively. The significance of this work rests with the ability of Raman spectroscopy to identify oxalates which often occur as a film on a host rock. As such, Raman spectroscopy has the potential to identify the existence or pre‐existence of life forms on planets such as Mars. Copyright © 2003 John Wiley & Sons, Ltd.

Rapid outdoor non‐destructive detection of organic minerals using a portable Raman spectrometer

“…From the large selection of known organic minerals, oxalic acid salts can be seen as structurally less complex and have the most common occurrence. Infrared (IR) and Raman spectra of synthetic [18 -20] and natural oxalates [21,22] have been obtained and interpreted. Edwards et al [23] have studied the occurrence of oxalates at the biogeochemical interface between rocks and lichens by Fourier transform (FT)-Raman spectroscopy with 1064 cm −1 excitation.…”

Studies of natural and synthetic agardites

“…In particular, Raman spectroscopy has been used to determine paragenetic relationships between many closely related phases FROST & KLOPROGGE 2003;FROST et al 2004;FROST et al 2003c;FROST & WEIER 2003;FROST et al 2003d). Agardite-(Ce), for example, is the mineral (CeCu 6 (AsO 4 ) 2 (OH) 6 .3H 2 O) as such the mineral has two vibrating units which will contribute to the NIR spectra, namely the hydroxyl units and the water HOH units.…”

Hygroscopic properties of oxalic acid and atmospherically relevant oxalates

“…The gray dashed line represents the Raman spectrum of iron (II) oxalate dihydrate. (Ebisuzaki and Angel, 1981;Frost, 2004;Frost and Weier, 2003;Mancilla et al, 2009;Moha cek-Gro sev et al, 2009). Previous studies always assigned the Raman shift bands in the range of 1610e1650 cm À1 to the stretching mode of C]O (Frost, 2004;Mancilla et al, 2009 particles.…”