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

Crystal structure of Melanterite

Formula:

Fe2+SO4•7(H2O)

Crystal Data:

Crystal System: Monoclinic - Prismatic

Point Group: 2/m

Cell Data:

Space Group: P 21/c, a = 14.11, b = 6.51, c = 11.02, Z = 4

Using the mouse (click here for more information)

Density (calc.) = 1.89 and V = 976.61 Å3
Element color: Fe, S, O
Melanterite sample
Melanterite

Synthetic sample




Click image to enlarge
Raman spectrum and vibrations of Melanterite
Element color: S, 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 melanterite (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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SO4 polyhedra on SO4 polyhedra off 		Vibrations:
ν2 SO4 ν4 SO4 ν1 SO4 ν3 SO4

Vibration on Vibration off 		Download spectrum:
Raman spectrum .txt Raman spectrum .spc


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Interpretation of Raman spectrum of Melanterite

The most intense Raman lines, corresponding to the ν1 symmetric stretching vibration of the sulfate group were found at 992 cm-1 for melanterite and 1024 cm-1 for bieberite. The ν2 mode of sulfate group was found at 457 cm-1 and 480 cm-1 in ferrous sulfate, and at 423 cm-1 and 495 cm-1 in bieberite; the ν3 mode presents lines at 1074 cm-1 and 1146 cm-1, respectively at 1069 cm-1 and 1181 cm-1. The peaks 611 cm-1 of melanterite, 623 cm-1 and 667 cm-1 of bieberite were assigned to the ν4 mode. In both spectra we observe peaks corresponding to water stretching modes, at 3385 cm-1 for melanterite and above 3400 cm-1 for bieberite. Chio et al., (2007) showed that increasing degrees of hydration, shift the intensity of the ν1 peak to lower wavenumbers.

In melanterite, the bands 214 cm-1, 241 cm-1 and 285 cm-1 are attributed to the translational modes T (Fe, H2O). In bieberite only two Raman bands appear, at 223 cm-1 and 285 cm-1. The melanterite spectrum shows some differences in bands position in Raman shift most probably due to analytical factors.


Bieberite Melanterite Assignments
Buzgar et al., 20091 Buzgar et al., 20091 Chio et al., 2007
223 214 206 T(M, H2O)
241 241
285 285 264
423 457 446 ν2 SO4
495 480 465
565 ν4 SO4
623 611 619
667
875
917		 ν(OH)
ν(H2O)
1024 992 976 ν1 SO4
1069 1074 1075 ν3 SO4
1102
1181 1146 1138
1625 ν(H2O)
1801 1648
3385 3371
3436
References

• The Mineralogy Database [link]

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

• 1BUZGAR N., BUZATU A., SANISLAV I. V. (2009) - The Raman study on certain sulfates. Analele Stiintifice ale Universitatii “Al. I. Cuza” - Iasi, Tome 55, issue 1, 5-23 [link]

• Chio, C. H., Sharma, S. K., Muenow, D. W. (2007) - The hydrates and deuterates of ferrous sulfate (FeSO4): a Raman spectroscopic study. Journal of Raman Spectroscopy, 38, 87-99.[link]