Raman microprobe spectroscopy of hydrated halloysite from a Neogene cryptokarst from Southern Belgium
✍ Scribed by J. Theo Kloprogge; Ray L. Frost
- Book ID
- 101249346
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 152 KB
- Volume
- 30
- Category
- Article
- ISSN
- 0377-0486
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✦ Synopsis
The Raman spectrum of single-crystal tubular hydrated 10 Å halloysite obtained by Raman microscopy clearly shows differences from dehydrated or metahalloysite. The hydroxyl stretching region shows two relatively strong asymmetric bands representing multiple bands n 1 and n 2 ascribed to the outer hydroxyl groups and n 3 and n 4 ascribed to the inner hydroxyl groups of the halloysite with two additional broad, lowintensity bands at 3556 and 3598 cm -1 . These bands are absent in dehydrated halloysite and are assigned to OH stretching modes of the adsorbed surface and interlayer water. Comparison between the 10 Å halloysite and metahalloysite shows that almost all bands observed for the hydrated halloysite are also observed for the metahalloysite, but with small differences in the band positions. These differences may indicate differences in crystal structure (interlayer water) or folding of the layers. New bands observed for the 10 Å halloysite are at 359 and 332 cm -1 , which are absent in all other kaolin minerals. Therefore, these vibrations are assigned to hydrogen-bonded water modes of adsorbed and interlayer water corresponding to the two hydroxyl stretching modes around 3556 and 3598 cm -1 .