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

Crystal structure of Aragonite

Formula:

CaCO3

Crystal Data:

Crystal System: Orthorhombic - Dipyramidal

Point Group: 2m/2m/2m

Cell Data:

Space Group: Pmcn, a = 4.959, b = 7.968, c = 5.74, Z = 4

Using the mouse (click here for more information)

Density (calc.) = 2.930 and V = 226.85 Å3

Element color: Ca, C, O
Aragonite sample
Aragonite

Sample no. 5473 from the "Mineralogy and Petrography Museum Grigore Cobălcescu" of "Alexandru Ioan Cuza" University, Iaşi.

Origin: Corund - Romania.




Click image to enlarge

Raman spectrum and vibrations of Aragonite
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 aragonite (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:
701 cm-1 - ν4b (E') 1083 cm-1 - ν1 (A'1) 1461 cm-1 - ν3a (E') 1573 cm-1 - ν3b (E')

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Download spectrum:
Raman spectrum .txt Raman spectrum .spc


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Interpretation of Raman spectrum of Aragonite

The characteristic Raman band due to the external vibration mode (M-CO3) at 250 cm-1, and the ν1 internal mode (symmetric stretching) at 1083 cm-1 are easily distinguished. In the Raman spectrum of the aragonite sample don't have values below 200 cm-1 because the spectral range is between 200-3400 cm-1.

In case of aragonite only four bands out of the 30 predicted Raman-active modes (J. Urmos et al., 1991) were detected in the Raman spectra of the aragonite sample no. 5473. This spectrum is governed by the very strong Raman line (1083 cm-1) atributed to the ν1 symmetric stretching mode of the carbonate group. The ν4 mode of CO3 has values at 701 cm-1. The ν2 vibration mode is not observed in this study; ν3 vibration are observed at 1461 and 1573 cm-1.

The frequencies of all Raman bands observed in Aragonite, Strontianite and Witherite can be corelated with the atomic masses of the cations.


Buzgar et al., 20091 Urmos, 1991 Krishnamurti, 1960 Assignment
250 284 285 T(Ca,CO3)
701 701
705
702
707
716
ν4 symmetric deformation
NO 853 854 ν2 asymmetric deformation
1083 1085 1086 ν1 symmetric stretch
1461
1573
1462
1547
1415
1463
ν3 asymmetric stretching
1547 NA
NO 2165 1

NO = not observed; NA = not assigned.
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]

• URMOS J., SHARMA S. K., MACKENZIE F. T. (1991) - Characterization of some biogenic carbonates with Raman spectroscopy. American Mineralogist, 76, p. 641-646 [link]

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