BEIDELLITE

Na_0.7Al₄(Si_7.3Al_0.7)O₂₀(OH)₄.xH₂O

Beidellite is a clay mineral of the smectite family (see Introduction to Clay Mineralogy). The name beidellite was given by Larsen and Wherry ¹ to a clay specimen from Beidell, Colorado, which they had earlier described as leverrierite ². Nowadays beidellite has been defined as a dioctahedral Al-smectite with an average layer charge of 0.6 to 0.7. This charge is completely created by the substitution of Si⁴⁺ by Al³⁺ on the tetrahedral positions. 

Kloprogge et al. ^3,4 observed that for synthetic beidellite in the infrared spectra the maxima had slightly shifted towards higher wavenumbers compared to natural beidellite ⁵. Russell ⁶ reported well-resolved OH-deformation bands at 915 cm^-1 for Al-OH-Al in beidellite, 840 cm^-1 for Al-OH-Mg in montmorillonite, and 890 cm^-1 for Al-OH-Fe²⁺ in e.g. Wyoming montmorillonite. For the synthetic beidellite a band was observed at 935 cm^-1 together with only one broad band around 800 cm^-1, whereas Russell ⁶ indicated two strong bands at 818 cm^-1 and 770 cm^-1. Recently, Kloprogge et al. ⁷ have made a comparison between several synthetic beidellites. These beidellites were characterised by Si-O bending vibrations shifted by approximately 5-10 cm^-1 towards higher wavenumbers compared to natural beidellite. Interlayer water was characterized by a single H₂O bending vibration at 1635 cm^-1 and a vibration due to H₂O-H₂O hydrogen bonds at 3450 cm^-1. The shoulder at 3220-3230 cm^-1 was ascribed to interlayer H₂O chemically bound or coordinated to the interlayer cation. A separate band was distinguished around 3645 cm^-1 assigned to OH-groups H-bonded to the non-charged Si-O-Si bond. The H-bonding of OH-groups to the charged Si-O-Al bond would occur around 3400 cm^-1, but this band was obscured by the stronger water-water H-bonding band at the same position.  

Original spectra shown for this mineral can be obtained on request from J.T. Kloprogge (E-mail t.kloprogge@qut.edu.au), or R.L. Frost (E-mail r.frost@qut.edu.au).

Postal address:

Centre for Instrumental and Developmental Chemistry, Queensland University of Technology, GPO Box 2434, Brisbane, Qld 4001, Australia.

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SELECTED REFERENCES ON SPECTROSCOPY OF BEIDELLITE:

  1.     Kloprogge, J.T., Jansen, J.B.H. and Geus, J.W. (1990) Characterization of synthetic Na-beidellite. Clays & Clay Minerals, 38, 409-414.

2.    Kloprogge, J.T., van der Eerden, A.M.J., Jansen, J.B.H. and Geus, J.W. (1990) Hydrothermal synthesis of Na-beidellite. Geologie & Mijnbouw, 69, 351-357.

3.    Kloprogge, J.T., Komarneni, S., Frost, R.L. and Fry, R. (1998) Infrared study of some synthetic and natural beidellites. Journal of Material Science Letters, 17, 1853-1855

4.    Kloprogge, J.T., Komarneni, S., Yanagisawa, K, Fry, R. and Frost, R.L. (1999) Infrared emission spectroscopic study of the dehydroxylation via surface silanol groups of synthetic and natural beidellite. Journal of Colloid and Interface Science, 212, 562-569.

5.    Kloprogge, J.T., Frost, R.L. and Hickey, L. (1999) Infrared absorption and emission study of synthetic mica-montmorillonite in comparison to rectorite, beidellite and paragonite, Journal of Material Science Letters, 18, 1921-1923.

6.    Kloprogge, J.T., Hickey, L. and Frost, R.L. (2000) The effect of increasing layer charge on the infrared absorption spectra of synthetic beidellites, Journal of Materials Science Letters, 19(13), 1131-1134.

7.     H. W. van der Marel, and H. Beutelspacher, “Atlas of Infrared Spectroscopy of Clay Minerals and their Admixtures” (Elsevier, Amsterdam, 1976).

8.     J. D. Russell, in “A Handbook of Determinative Methods in Clay Mineralogy” edited by M. J. Wilson (Blackie, Glasgow 1987), 133.

9.     V. C. FARMER, in “The Infrared Spectra of Minerals” edited by V.C. Farmer, (Mineral. Soc. London, 1974) 331.