BaSO4
Barite [BaSO4], also known as baryte, crystallises in an orthorhombic Pnma (D2h16) structure. It is used as a thermo-luminescent dosimeter of gamma rays, and in the production of paint and paper 1. In barite, cation Ba is surrounded by twelve oxygen anions belonging to seven different SO4 molecules 2. Baldyrev 3 also reports substitution of SO4 group by two NO3 groups.
The fundamental vibrational modes of the SO4 molecule are known as four distinct internal modes, i.e. one nondegenerate mode v1, one doubly degenerate mode v2, and two triply degenerate modes v3 and v4. The IR spectrum of barite has two strong bands v3 and v4, and one weak band v1 2. There is a significant disagreement among reported spectra for barite. Only one reference reports the presence of water in the IR spectrum of barite at 3430 and 1650 cm-1 4. While two references found band at 980 cm-1 assigned to v1 2,5, only Farmer 5 observes v2 vibrational mode at 470 and 439 cm-1. Vibrational mode v3 is reported to have bands at 1180, 1120 and 1080 cm-1 2, while Farmer 5 finds these bands at 1205, 1136, 1100 and 1042 cm-1 . Similarly, vibrational mode v4 is shown at 633 and 608 cm-1 2, and is also reported at 641, 633 and 614 cm-1 5. Barite bands are also found in the far infrared region at 198, 167, 142, 125 and 100 cm-1 2. Bands at 2350, 1470, 1330 and 725 cm-1 have been observed in some IR spectra of barite 4.
The strongest band in the Raman spectrum of barite occurs at 987 cm-1, followed by bands found at 460 and 451 cm-1. Other weaker bands are resolved at 1167, 1140, 1083, 646, 630, and 617 cm-1 6.
1. Nikolic, P.M., Dimitrijevic, P.M., Stojilkovic, S.M., Sekulic,M., and Mihajlovic, P.R. (1980). Optical properties of the orthorhombic mineral barite., Fizika (Zagreb), 12(Suppl.1), 169-173.
2. Omori, K. (1968). Infrared diffraction and the far infrared spectra of anhydrous sulfates. Mineralogical Journal, 5(5), 334-354.
3. Boldyrev, A.I. and Povarennykh, A.S. (1968). Infrared absorption spectra of the main carbonate and nitrate minerals., Mineral. Sb. (Lvov), 22(1), 11-21.
4. J.A. Gadsden 1975. Infrared spectra of minerals and related inorganic compounds. Butterworths, London. Pp96.
5. V.C. Farmer, 1974 Infrared spectra of minerals in Mineralogical Society Monograph 4 VC Farmer (Ed) pp 427. Mineralogical Society, London.
6. Griffith, W.P. (1970) Raman studies on rock-forming minerals. II. Minerals containing MO3, MO4 and MO6 groups. J. Chem. Soc. A(2), 286-91.
SELECTED REFERENCES ON SPECTROSCOPY OF
BARITE:
1. Omori, K. (1968). Infrared diffraction and the far infrared spectra of anhydrous sulfates. Mineralogical Journal, 5(5), 334-354.
2. V.C. Farmer, 1974 Infrared spectra of minerals in Mineralogical Society Monograph 4 VC Farmer (Ed) pp 427. Mineralogical Society, London.
3.
J.A. Gadsden 1975. Infrared spectra of minerals and related inorganic
compounds. Butterworths, London. Pp96.
4. Griffith, W.P. (1970) Raman studies on rock-forming minerals. II. Minerals containing MO3, MO4 and MO6 groups. J. Chem. Soc. A(2), 286-91
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.
Fax +61
7 3864 1804
For more information see our general website at: http://www.sci.qut.edu.au/sci_schps.html
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