title: Comment on "A spectroscopic comparison of selected Chinese kaolinite, coal bearing kaolinite and halloysite--a mid-infrared and near-infrared study" and "Infrared and infrared emission spectroscopic study of typical Chinese kaolinite and halloysite" by Hongfei Cheng et al. (2010).
abstract: In two papers Cheng et al. (2010) reported in this journal on the mid-infrared, near-infrared and infrared emission spectroscopy of a halloysite from Hunan Xianrenwan, China. This halloysite contains around 8% of quartz (SiO2) and nearly 9% gibbsite (Al(OH)3). In their interpretation of the spectra these impurities were completely ignored. Careful comparison with a phase pure halloysite from Southern Belgium, synthetic gibbsite, gibbsite from Minas Gerais, and quartz show that these impurities do have a marked influence on the mid-infrared and infrared emission spectra. In the near-infrared, the effect is much less pronounced. Quartz does not show bands in this region and the gibbsite bands will be very weak. Comparison still show that the presence of gibbsite does contribute to the overall spectrum and bands that were ascribed to the halloysite alone do coincide with those of gibbsite.
authors.affiliation: School of Earth Sciences, The University of Queensland, St. Lucia, Queensland 4072, Australia. Electronic address: j.kloprogge@uq.edu.au.
authors.forename: J Theo
authors.initials: JT
authors.lastname: Kloprogge
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry*; D003031:Coal; D007616:Kaolin / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D000538:Aluminum Silicates; D003031:Coal; D007616:Kaolin
keywords: Gibbsite; Halloysite; Hydroxyl; Infrared spectroscopy