Infrared characterization of water and hydroxyl ion in the basic magnesium carbonate minerals

Abstract

Infrared spectra in the 0.5-50 m range have been measured on nesquehonite (MgCO 3 .3H 2 O, artinite (MgCO 3 .Mg(OH) 2 .3H 2 O) and hydromagnesite (4MgCO 3 .Mg(OH) 2 .4H 2 O). The CO 3 2- internal vibrations are sharp in hydromagnesite and unexpectedly broad and diffuse in artinite and nesquehonite. The OH - stretching region contains a sharp band indicative of a weak, well defined hydrogen bond in all three minerals. There is also a broad band characteristic of moderately strong and less well defined hydrogen bonds in all three. In addition hydromagnesite has two sharp intense bands not present in the other two minerals. The artinite spectrum is interpretable by Jagodzinski's structure and nesquehonite appears to be similar. Hydromagnesite should have a distinctly different structure. There is no evidence for bicarbonate groups in nesquehonite.