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Witherite: Crystal structure | Sample photo | Raman spectrum | Interpretation | References

Crystal structure of Witherite

Formula:

BaCO3

Crystal Data:

Crystal System: Orthorhombic - Dipyramidal

Point Group: 2m/2m/2m

Cell Data:

Space Group: Pmcn, a = 5.313, b = 8.904, c = 6.43, Z = 4

Using the mouse (click here for more information)

Density (calc.) = 4.31 and V = 304.18 Å3

Element color: Ba, C, O
Witherite sample
Witherite

Sample no. 5484 from the "Mineralogy and Petrography Museum Grigore Cobălcescu" of "Alexandru Ioan Cuza" University, Iaşi.

Origin: Alston - England.




Click image to enlarge

Raman spectrum and vibrations of Witherite (no. 5484)
Element color: C, O Toggle Grid Toggle Coordinates Reverse Spectrum

Click to in the Raman spectrum. To see the vibrations click on one of them (highlight region) and it (the selected vibration) will appear on the right side of the Raman spectrum.
Below spectra are various settings, and other vibrations of witherite (which are not present in this spectrum).
You have the possibility to zoom in the spectrum by selecting a spectral region you need to be increased (along axis x); to zoom keep the left mouse-click continously pressed, drag (to left or to right) and release the left button. To return to the initial size spectrum, press the right click on the spectrum -> Zoom -> Reset View.

Model type:
Sticks Ball-and-Sticks (1) Ball-and-Sticks (2) CPK (Spacefill)

Orientation:
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Background color:
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CO3 polyhedra on CO3 polyhedra off
Vibrations:
693 cm-1 - ν4b (E') 1059 cm-1 - ν1 (A'1) 1422 cm-1 - ν3a (E') 1511 cm-1 - ν3b (E')

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Download spectrum:
Raman spectrum .txt Raman spectrum .spc
Raman spectrum .txt Raman spectrum .spc

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Raman spectrum of synthetic Witherite (BaCO3)
Interpretation of Raman spectrum of Witherite

The characteristic Raman band due to the external vibration mode (M-CO3) at 227 cm-1 and 222 cm-1, 285 cm-1 for witherite and synthetic BaCO3, respectively, and the ν1 internal mode (symmetric stretching) for both witherite sample at 1059 cm-1 are easily distinguished. In the Raman spectrum of the witherite and synthetic BaCO3 samples don't have values below 200 cm-1 because the spectral range is between 200-3400 cm-1.

The Raman spectra for the witherite and synthetic BaCO3 are very similar the only differences are found in the 200-300 cm-1 region. In the synthetic BaCO3 spectra appear one peak in addition at 285 cm-1 attributed to the external vibration mode. As can be seen in Raman spectra, witherite and BaCO3 synthetic do not present values below 200 cm-1 because the spectral range is between 200-3400 cm-1. The intense ν1 symmetric stretching mode of carbonate group is at 1059 cm-1 for both spectra. The bands at 1422 cm-1 and 1421 cm-1 are due to the ν3 asymmetric stretching mode, and the bands at 1511 cm-1 and 1508 cm-1 are not assigned. The ν2 vibration mode is not observed. The Raman line at 693 cm-1 is attributed to ν4 vibration.


Buzgar et al., 20091 Buzgar et al., 20091 Krishnamurti, 1960 Beny, 1989 Assignment
sample no. 5484 synthetic BaCO3
227 222, 285 227 224 T(M,CO3)
693 693 691
699
690
696
v4 - symmetric deformation
NO NO 852* v2 - asymmetric deformation
1059 1059 1061 1035
1059
v1 - symmetric stretch
1422
1511
1421
1508
1394
1409
1421
1419
1505
v3 - asymmetric stretching
NO NO 2116* 2v1
The frequencies marked with asterisk are reported for the first time.
NO = not observed.
References

• The Mineralogy Database [link]

• Crystal data (.cif file) from the American Mineralogist Crystal Structure Database [link]

1BUZGAR N., APOPEI A. I. (2009) - The Raman study on certain carbonates. Analele Stiintifice ale Universitatii “Al. I. Cuza” - Iasi, Tome 55, issue 2, 97-112 [link]

• KRISHNAMURTI D. (1960) - The Raman spectra of aragonite, strontianite and witherite. Indian Academy of Sciences [link]

• BENY C. (1989) - Societe Francaise de Mineralogie et de Cristallographie - Base donnees de spectres Raman. Witherite [link]