BRUCITE

Mg(OH)₂

Brucite is a mineral which is of commercial importance. The dehydroxylated products of brucites have potential application as catalysts. However the natural mineral is often contaminated with other magnesium minerals such as dolomite and serpentinite. Brucite (Mg(OH)₂) is a layered hydroxide with two sheets of hydroxyls parallel to the basal plane and with a sheet of Mg ions between these hydroxyls which are in hexagonal close packing with each of the hydroxyls linked to three Mg on the one side and fitted into three hydroxyls of the next layer.  In comparison with gibbsite where only two of the three cation sites are occupied, all three sites are occupied in brucite ¹. In both these minerals, the layers are regarded as built of octahedra linked laterally by sharing edges. The most common occurrence of brucite is as the alteration product of periclase (MgO) in contact with metamorphosed dolomites ^2-3.  Consequently pure naturally occurring brucite minerals are difficult to obtain and often contain impurities of dolomite, talc serpentinite and other magnesium minerals.

Farmer reported the hydroxyl stretching frequency of magnesium hydroxide at 3698 cm^-1 with the deformation vibration at 415 cm^{-1 4}.  The Raman hydroxyl stretching frequency was reported at 3653 cm^-1. There are considerable differences in the band positions of brucites reported in the literature.  Gadsden reported brucite hydroxyl stretching bands at 4290, 4050, 3730, 3570, and 3290 cm^-1 in the hydroxyl-stretching region ².  Van der Marel reported brucite hydroxyl stretching bands at 3698 and 3275 cm^-1 in the hydroxyl-stretching region ³. 

1.     W.A. Deer, R.A. Howie and J. Zussman, An introduction to the rock forming minerals, 1996. Addison Wesley Longman, Harlow, Essex, England pp571-2.

2.    J.A. Gadsden 1975. Infrared spectra of minerals and related inorganic compounds. Butterworths, London. Pp55.

3.    H. W. van der Marel and H. Beutelspacher, Atlas of Infrared spectroscopy of clay minerals and their admixtures, Elsevier, Amsterdam, The Netherlands. 1976. pp224-229.

4.    V.C. Farmer, 1974 Infrared spectra of minerals in Mineralogical Society Monograph 4 VC Farmer (Ed) pp 138-139. Mineralogical Society, London.

SELECTED REFERENCES ON SPECTROSCOPY OF BRUCITE:

1.    Frost, R.L. and Kloprogge, J.T. (1999) Infrared emission spectroscopic study of brucite. Spectrochimica Acta, 55, 2195-2205.

2.    Frost, R.L. and Kloprogge, J.T. (2000) The application of near-infrared spectroscopy to the study of brucite and hydrotalcite structures. Canadian Journal of Analytical Science and Spectroscopy, 45(4), 96-102.

3.    J.A. Gadsden 1975. Infrared spectra of minerals and related inorganic compounds. Butterworths, London. Pp55.

4.     H. W. van der Marel and H. Beutelspacher, Atlas of Infrared spectroscopy of clay minerals and their admixtures, Elsevier, Amsterdam, The Netherlands. 1976. 224-229.

5.    V.C. Farmer, 1974 Infrared spectra of minerals in Mineralogical Society Monograph 4 VC Farmer (Ed) pp 138-139. Mineralogical Society, London.

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).

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