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

Crystal structure of Rhodochrosite

Formula:

MnCO3

Crystal Data:

Crystal System: Trigonal - Hexagonal Scalenohedral

Point Group: 3 2/m

Cell Data:

Space Group: R 3c, a = 4.777, c = 15.67, Z = 6

Using the mouse (click here for more information)

Density (calc.) = 3.70 and V = 309.68 Å3

Element color: Mn, C, O
Rhodochrosite sample
Rhodochrosite

Sample no. 5438 from the "Mineralogy and Petrography Museum Grigore Cobălcescu" of "Alexandru Ioan Cuza" University, Iaşi.

Origin: Kohlenbach - Germany.




Click image to enlarge

Raman spectrum and vibrations of Rhodochrosite
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 rhodochrosite (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)

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CO3 polyhedra on CO3 polyhedra off
Vibrations:
726 cm-1 - ν4b (E') 1094 cm-1 - ν1 (A'1) 1439 cm-1 - ν3a (E')

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Download spectrum:
Raman spectrum .txt Raman spectrum .spc


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Interpretation of Raman spectrum of Rhodochrosite

The Raman spectrum of rhodochrosite consists in a strongest intensity band at 1094 cm-1 assigned to symmetric stretching mode ν1 of CO3 group, the ν3 mode appears at 1439 cm-1 and the ν4 mode at 726 cm-1.

The observed vibrational bands of rhodochrosite compared with well-documented values are listed below. The minor shift in positions may be due to the effects of natural impurities present in the sample.


Buzgar et al., 20091 Beny, 1991 Free CO32- Assignment
R*(CO3)
184 T(Ca, CO3)
293 289 T(Ca, CO3)
726 718 680 ν4 symmetric CO3 deformation
879 ν2 asymmetric CO3 deformation
1094 1064
1085
1063 ν1 symmetric CO3 stretching
1439 1414 1415 ν3 asymmetric CO3 stretching
1752 1725 ν1 + ν4

R* - rotational

The lower wavenumbers of rhodochrosite (293 cm-1) observed in the above table, arise from the external vibration of the CO3 group that involve translatory oscillations of the group (relative translations between the cation and anionic group). In this spectrum are no values below 200 cm-1 because the spectral range is between 200 - 3400 cm-1.

A weak line observed at 1729 cm-1 may be regarded as the combination band of ν1 + ν4.

The positions of the observed Raman bands are in agreement with those reported by Beny C., 1991.

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]

• BENY C. (1991) - Societe Francaise de Mineralogie et de Cristallographie - Base donnees de spectres Raman. Rhodochrosite [link]