- journal_title：Clays and Clay Minerals
- Contributor：Cliff T. Johnston ; Jessica Elzea Kogel ; David L. Bish ; Toshihiro Kogure ; Haydn H. Murray
- Publisher：Clay Minerals Society
- Date：2008-
- Format：text/html
- Language：en
- Identifier：10.1346/CCMN.2008.0560408
- journal_abbrev：Clays and Clay Minerals
- issn：0009-8604
- volume：56
- issue：4
- firstpage：470
- section：Articles
Low-temperature FTIR spectroscopy was used to characterize the ν(OH) region of kaolin-group minerals including well ordered to poorly ordered kaolins from Georgia, Brazil, and England, along with samples of discrete dickite and nacrite. Low-temperature FTIR spectra were useful in resolving dickite- and nacrite-like features present in the spectra of kaolins when cooled to <30 K. These features were not resolved at room temperature and only partially resolved at liquid N2 temperature (77 K). The room-temperature and low-temperature positions of the ν(OH) bands of kaolinite, dickite, and nacrite were linearly correlated with the interatomic OH···O distances and this relationship served as the basis for polytype/disorder identification. Dickite or dickite-like disorder was found in high Hinckley-Index kaolinite from Keokuk, Iowa, and from Cornwall, England. Dickite- and nacrite-like features were observed in both high- and low-Hinckley-index kaolinite and the amounts of these stacking sequences generally increased with decreasing Hinckley Index.